The Quarterly Journal of Experimental Psychology Section A
ISSN: 0272-4987 (Print) 1464-0740 (Online) Journal homepage: http://www.tandfonline.com/loi/pqja20
Do visual images have gestalt properties? Pertti Saariluoma To cite this article: Pertti Saariluoma (1992) Do visual images have gestalt properties?, The Quarterly Journal of Experimental Psychology Section A, 45:3, 399-420, DOI: 10.1080/02724989208250621 To link to this article: http://dx.doi.org/10.1080/02724989208250621
Published online: 29 May 2007.
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THE QUARTERLY JOURNAL OF EXPERIMENTAL PSYCHOLOGY, 1992,45A (3) 3 W 2 0
Do Visual Images have Gestalt Properties? Pertti Saariluoma
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University of Helsinki, Finland
Recent research has demonstrated that percepts and images share processing resources. A natural consequence of this evidence is to ask what kind of properties are shared by the two representational systems, i.e. images and percepts. To what degree, for example, do images share the complex organization of visual percepts? This paper investigates whether percepts and images share Gestalt properties. Four experiments were conducted to study this hypothesis. In all experiments subjects were presented with an auditory message in which approximately 15 locations in a matrix were defined by giving the co-ordinates of the cells. Half of the stimuli presented some “good” form, whereas in the other half the locations of the pieces were scattered. Subjects were systematically less able to recall the locations of the random forms. Therefore, it could be argued that the “good” forms help in image construction, even though the elements were auditorily presented. Effects of varying presentation speed, order, and of requiring a mental rotation before recall support this conclusion,
Consistent evidence has been found for the overlapping cognitive and neural processing resources of visual images and percepts (Farah, 1985; Finke, 1980,1985;Kosslyn, 1987). The most obvious evidence is the experience of images. They are reported to be more like percepts than stories. Thus, we are able to recall the colour of a continuous object, though we are unlikely to be able to describe all the points on its surface verbally. The experience of an image is not, of course, sufficient argument for shared processing resources, but the number of objective observations that supRequests for reprints should be sent to Pertti Saariluoma, Department of Psychology, University of Helsinki, Fabianinkatu 28, 00100 Helsinki 10, Finland. I am very grateful to Robert H. Logie and an unknown referee for their helpful comments and suggestions. I would also like to thank Lauri Oksama, Tiina Takala, and Michael Miettinen for running the experiments and Mark Shackleton, Lecturer in English at the University of Helsinki, for correcting the language. The research has been supported by the Academy of Finland. @ 1992 The Experimental Psychology Society
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port overlapping resources has grown substantially during the last ten to fifteen years or so (Farah, 1988; Finke, 1985). Consequently, it is now fairly safe to assume the existence of shared processing resources and to try to define precisely the overlapping parts of the percepts and images. An argument for the shared processing resources for images and percepts is the high percept-like character of some forms of images such as eidetic images. This form of imagery is so vivid and close to percepts that eidetic images have sometimes been called “photographic memories” (Richardson, 1969). This phenomenon appears to be virtually decisive evidence in support of shared processing resources. However, only a small part of the population can produce eidetic images, and therefore eidetic images can hardly be taken as a crucial argument for shared representational resources between images and percepts (Harber, 1979). It may only be argued that the existence of the phenomenon could hardly be possible without any connections between percepts and images. Stronger evidence can be found in image-percept interference and interaction experiments, which show that mental images and visual percepts interfere with each other. A classic experiment by Segal and Fusella (1970) showed that image interference in detecting perceptual stimuli is larger in isomodal than cross-modal conditions. It has later also been shown that images may cause selective facilitation in the perception of a stimulus. Farah and Smith (1983), for example, have shown that auditory images may facilitate perception of the same frequency signals. The contradictory findings suggest that percepts and images may interact and share the representational resources. A very clear example of imaging interference effects can be found in experiments on visual working memory (Baddeley, 1986; Baddeley & Hitch, 1974). Visuo-spatial secondary tasks usually strongly interfere with visual-memory and imagery tasks (Baddeley, 1986, 1988). Even unattended pictorial material may cause some processes to deteriorate. As Logie (1986) showed, unattended pictures interfere with the use of imagery-based mnemonics. Numerous experiments demonstrate the solidity of imaging interference on the processing of visuo-spatial materials. Even experts in a field suffer from imaging interference. Bradley, Hudson, Robbins, and Baddeley (1987) found a strong imaging interference effect in chess players’ recall of chess positions. Similarly, Saariluoma (1991a, 1992) has shown that chess players’ calculation of variations suffers from imaging interference. A third link between images and percepts is to be seen in functional imagery experiments. Mental rotation, transformation of size, image overflow, scanning, and comparison of imagined objects all show effects that are highly analogous with the physical manipulation of the same objects (Bundesen & Larsen, 1975; Kosslyn, 1980; Cooper & Shepard, 1973;
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Shepard & Metzler, 1971). Paivio (1978), for example, asked subjects to select from two clock times the one in which the angular distance between the hands was smaller and found that the comparison reaction time increased as the difference decreased. Similar differences were found with pictures of clocks. An extensive literature also shows that concrete, i.e. visible, objects and their names can be recalled better than abstract objects, i.e. objects that are not highly visible (Paivio, 1971, 1986). Additionally, if the subjects are able to form an image of a word that is close to a percept, it is more likely that they will recall it than a case where the word is somewhat abstract (Paivio, 1971, 1986; Richardson, 1980). This also suggests that percepts and images are close to each other. Finally, Farah (1988) has presented strong neuropsychological evidence for a shared representational medium for images and percepts. Though the above-mentioned lines of research provide clear evidence for shared representations, none of them suggests total overlap. If images and percepts do not share all the processing resources, it must be asked to what degree overlap does exist. In addition, which properties of visual percepts are important in processing images, and which are not? A very evident property of percepts that could be compared with images is their high level of organization. Do images share some organizational aspects with percepts? Do images have, for example, Gestalt properties? The latter question is the main topic of this paper. Gestalt psychologists have shown how the human perceptual system is able to organize meaningless patterns of lines and dots into “meaningful” wholes by using relatively simple principles, such as similarity, symmetry, proximity, good continuation, etc. (Lasaga, 1989; Kohler, 1935; Wertheimer, 1923). If images and percepts do share processing resources, a very interesting question arises, namely, whether people also use the same principles of good organization in constructing images that they use in constructing percepts. Memory experiments with dot matrixes and some meaningless forms show that a good Gestalt improves the recall of visual patterns (Asch, Ceraso, & Heimer, 1960; Garner, 1974). This suggests that visual images share Gestalt properties with visual images. Unfortunately, the experiments with visually presented stimuli cannot provide unambiguous evidence for the sharing of organizational resources, because the stimuli have first been encoded visually, and therefore the origin of organization may be on the visual rather than the imagery level. Subjects might simply be able to benefit from “good forms” because they have stored the visual trace information in their long-term memory. It might be that they could not encode the “good” forms unless the shapes had been first processed by the resources responsible for the visual but not the imagery processing.
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On the other hand, people use mental images and benefit from them in encoding verbal materials. People with vivid visual images understand prose better than less vivid imagers (see Denis, 1982). It is also known that people often use visuo-spatial working memory for encoding and storing verbal information (Baddeley, 1986). Saariluoma (1991b), for example, presented chess positions auditorily for recall to chess players to test recall and found a strong concurrent imaging interference effect, although articulatory performance level was well over 90% with skilled chess players. Therefore, it may be assumed that subjects’ mental images can be studied by representing auditorily a task whose basic task demands are spatial. Consequently, in the present experiments the mode of stimulus representation was changed compared to earlier experiments on Gestalt effects in recall. Instead of presenting the patterns to be recalled visually, they were presented auditorily. The locations to be recalled were specified by verbally giving the x and y co-ordinates of an imaginary matrix. It was assumed that if subjects could still benefit from the “good” forms of presented groups of dots, it is a sign that images share some organizational properties with percepts. As the pattern “goodness” was varied in the Gestalt sense, the organizational properties should be the Gestalt properties of the stimuli. It is important for our concept of image if it can be shown that subjects are better able to recall “good” forms than random ones, because Gestalt properties are usually thought to be encoded at a very early stage of processing (Kosslyn, 1991; Marr, 1982; Pylyshyn, 1978). Verbally presented propositions cannot have any visual Gestalt properties themselves, and they must be added into representation by the processing system. If images really do have Gestalt properties and their origin can be found, it will undoubtedly increase our understanding of images and the mechanisms of “Gestalts”.
GENERAL METHOD In all experiments subjects were asked to recall the locations of a set of 14 to 15 dots “placed” on an imaginary 8 X 8 matrix. The locations of the dots were read to them using a tape recorder. The location of each dot was specified by using a chessboard- or spreadsheet-type notational system: a cell in the matrix was specified by reading its co-ordinates, one of which was a letter (a-h) and the other a number (1-8). The expression “al” specified, therefore, one cell, and “a2” or “bl” two of its adjacent cells. The matrix on which the dots were recalled was visible for the subjects during the presentation, but they were only allowed to put pieces on it after all the dots had been read out from the tape. Therefore, they had to
GESTALT PROPERTIES IN IMAGERY Random
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FIG. 1. Four examples of stimuli: two good and two random forms.
construct the locations of objects in their mental image. Two examples of “good” and “random” forms are presented in Figure 1. It was assumed that each cell read out contained a dot, and the subjects were asked to recall as many dots as possible immediately after the presentation was over. Recall was made by placing black draughts pieces, referred to here as dots, on the verbally specified squares on a real board. The number of correctly placed pieces was scored, and the results present the average percentage of correctly placed dots per stimulus position. The forms of dot groups were manipulated either by letting them form some “good” shape such as a square, symmetrical rows, a triangle, the letter Z, and so on, or by scattering the locations randomly. If subjects are able to use Gestalt properties of images in encoding the auditory messages, they should be substantially better in recalling good forms than in recalling random forms.
EXPERIMENT 1 The main interest of this experiment was whether the subjects could benefit from the “good” Gestalt of the well-organized dot patterns, though the presentation was auditory and they could not, therefore, use their visual system in stimulus organization. A positive answer to the question would provide prima facie evidence for shared organizational resources. Another question the experiment was designed to answer was the effect of the speed of presentation. Saariluoma (1989) has shown that chess players’ recall of auditorily presented chess positions suffers from a faster speed of presentation, even though this does not cause any qualitative effects. The reading was varied in this experiment in order to find a suitable speed.
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Method
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Subjects. Eight subjects were used; they were first-year psychology students at the University of Helsinki, and they were given a course credit for their participation. Stimuli. Twenty dot matrixes were read onto a tape. In half of them the dots formed a “good” pattern (Kohler, 1935), in the other half, the dots were scattered in the matrix. The locations of the dots were read onto a tape either at a speed of one location per second or one location every two seconds. They were read out from left to right, from top to bottom. In this way four sets of five stimuli were acquired: “good” form at one dot per sec, random form at one dot per sec, “good” form at one dot every 2 sec, and random form at one dot every 2 sec. To control the possible differences between the read positions, a second tape was made in which the stimuli that had been read at the speed of one dot per sec were read at the speed of one dot every 2 sec and vice versa. Half of the subjects were presented with the first tape and the other half with the second tape.
Procedure. The stimuli were presented to the subjects in randomized order. Subjects heard one set of stimuli-i.e. one array-at a time, and they were required to recall all the dots in that array immediately after they had heard the location of the last dot. Therefore, they had to rely on their image of the locations. Recall was made by placing round draughts pieces on a white matrix of cells.
Results and Discussion The results of the experiments are presented in Figure 2. For clarity, the means of “good” vs. random shape and presentation time 1 vs. 2 sec have been presented separately. The differences between “good” vs. random shape comparisons are very clear, the absolute difference in means being almost 40%. The difference is statistically significant, F(1, 7) = 139.7, p < 0.001. The results of the first experiment thus support the main hypothesis. Though the presentation is auditory, subjects benefit from “good” forms. To recall the dot locations, subjects form an image of the matrix, and they locate the dots on that image. If the shape of a pattern is “good”, they can chunk it, as a good chess player can chunk chess-specific patterns, more easily and store it in long-term memory (Saariluoma, 1989). The speed of reading effect is quite large and statistically significant, F(1, 7) = 26.46, p < 0.001. There was no significant interaction between the conditions. Presumably, the speed of reading effect is caused by the
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FIG. 2. Time and pattern goodness. The effects of time and presentation order on recall. Goodl = “good” pattern, one sec; Good2 = “good” pattern, two sec; Random1 = randomized pattern, one sec; Random2 = randomized pattern, two sec (percentages of correctly recalled locations).
time it takes to form a visuo-spatial representation. Subjects lose dots because they have not yet been able to encode adequately the previously presented dots. The increased speed causes an overflow in image construction. This overflow, however, is roughly the same in both conditions, and the interaction between conditions was not significant [F(l, 7) = 2.891. An important question is the possible influence of verbal labels on recall. The literature cited in the introduction suggests that subjects may better recall “good” forms that are easy to name than “good” forms that are difficult to name. This issue can be studied in a post hoc manner by dividing the “good” stimuli into two equally large groups: easily nameable items (e.g. diamond, cross) and very difficult or non-nameable items (see Appendix). A group of ten subjects were asked to classify the “good” stimuli into difficult and easily nameable ones. The absolute number of classifications into easily nameable category was taken as the measure of the ease of nameability. When this nameability measure was correlated with the recall probability of the stimuli using Spearman’s rank correlation, no dependency could be found (p = 0.07, n.s.).
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Subjects regularly made errors of commission, and these errors provide further information about the cognitive mechanisms behind subjects’ “good” Gestalt superiority. These errors can be looked at from two different points of view: (1) it is possible to compare the location of an erroneous dot with the presented stimulus, and (2) it is possible to compare it with the recalled dots. To study the first aspect of the errors, they were allocated two two classes: in one class were put all the errors in which subjects had placed a piece into a cell next to some actually existing piece, in the other class all the pieces that were not immediately adjacent to some piece read to the subjects. The errors belonging to the first class were termed adjacent errors and the errors in the latter class non-adjacent errors. The adjacent vs. non-adjacent classification may be assumed to provide information about the blindness of guessing. If the pieces are located close to correct locations, it suggests that subjects have had some idea about the location of the dot. If the errors of commission are spread randomly over the board, they are caused by blind guessing. In the first experiment the results were clearly biased towards adjacency errors in all four conditions. The percentages of the eight types of errors of all 344 errors of commission are presented in Table 1 (top). Subjects make surprisingly large numbers of adjacency errors. They are more probable, but this cannot be explained solely on the basis of random guessing. The probability of putting a piece randomly on a non-adjacent square is 0.25 and to an adjacent square 0.52 with “good” formed positions. With random positions the corresponding probabilities are 0.12 and 0.64. However, in “good” positions adjacent errors are approximately 40 times more common than non-adjacent, and even in random positions the empirical probability is 12 to 27 times larger. The empirical ratios are clearly TABLE 1 Adjacent and Non-adjacent Location Errors (Top) and Continuous and Discontinuous Location Errors (Bottom Panel)
GI
G2
RI
R2
Total
Adjacent Non-adjacent Total
13 0 13
15 0 15
26 2 28
42 1 43
96 3 100
Continuous Discontinuous Total
12 3 15
15 12 27
12 3 15
31 12 43
70 30 100
Percentages of all errors of commission.
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larger (2-3 times) than one would expect on the basis of expected probabilities. This suggests that in making an error of commission a subject has some overall idea about the location of the dot, but he or she has not been able to encode it precisely. The other classification of the errors of commission is based on their relation to recalled dots, real or imaginary. If a dot is located erroneously next to some other recalled dot, it is a continuity error. If no dots are placed in cells adjacent to it, it is classified as a discontinuous error. The continuity properties of errors are assumed to provide information about the Gestalt properties of the recalled form. It may be argued that a dot that is placed next to some other shares a “good continuity” or proximity property with the other dot. So the probability with which subjects place a piece erroneously next to another piece may provide information about the chunking mechanisms subjects use in these kinds of tasks. The distribution of errors in eight main conditions has been presented in Table 1 (bottom). The distribution is quite similar to that shown in the top panel in Table 1, although the continuouddiscontinuous difference in Table 1 is smaller than the corresponding adjacenthon-adjacent difference, and the “good” vs. “random” pattern asymmetry is somewhat smaller. The superiority of continuous over discontinuous errors suggests that subjects try to encode larger wholes than just single pieces. However, they may often fail in locating their chunks precisely. The results support the claim that subjects use and benefit from some Gestalt principles in representing auditorily presented dot groups. “Good” pattern superiority is very clear, and there is no evidence for the assumption that it is caused by naming. The analysis of errors also shows that continuity and adjacency errors are frequent. This suggests that the errors of commission are not caused by blind guessing but reflect rather chunking mechanisms. Subjects often rely on an overall impression of the dot locations, and they also use continuity properties of dot groups. An interesting problem is, of course, why subjects make more commission errors with random stimuli if these errors are caused by chunks, which are partly made by using Gestalt principles. The explanation is that the subjects are also able to extract such chunks in random positions. The size of these chunks is just substantially smaller.
EXPERIMENT 2 Though the first experiment provided evidence for the use of Gestalt principles in constructing mental images, it may be thought that the order of the presentation of the dots with scattered patterns may be more random with random than with “good” patterns. One might think, for example, that the dots in “good” forms are somehow more regular when read from
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left to right than are the scattered patterns. Therefore, it might be that the difference between random and “good” forms is due to the organization of the presented dot sequences ’and has nothing to do with the images themselves. To study possible sequence order effects in “good” pattern superiority the order of presentation was varied. If “good” pattern superiority disappears when the dot sequences are presented in random order and not from left to right, it can be argued that the difference between “good” and random forms was not caused by imagery level effects but rather by the difficulties in organizing the encoding of scattered patterns into propositions.
Method Subjects. Eight subjects participated in the experiment. They were all students from an elementary course in psychology, and they received a course credit for participating in the experiment. Stimuli. The same dot patterns were used as in the previous experiment; the only difference was that instead of varying the reading speed, the reading order was varied. In ordered reading five “good” forms and five random dot patterns were presented at the speed of one dot every 2 sec starting from left and proceeding to the right. In random reading order five “good” and five random forms were presented, so that the presentation order of dots was not regular but random. Again two complementary tapes were used. Procedure. The procedure was the same as in the first experiment.
Results and Discussion Reading order is an important factor. The random order substantially decreases the performance level; the difference is large and statistically significant, F(1, 7) = 74.72, p < 0.001. A randomized presentation order clearly impairs recall of the dot patterns (Figure 3). However, the results do not support the critical hypothesis. Not only “good” patterns suffer from the randomized presentation order; the recall of random patterns is evidently impaired by the randomized presentation, F(1, 7) = 50.55, p < 0.001, though the interaction is clear, F(1, 7) = 13.36, p < 0.001. The results of the previous experiment were thus not accidental for a “good” shape makes it easier to build a visuo-spatial representation of auditorily presented sets of dots. The comparison between easy-to-name and difficult-to-name stimuli provided no new information. Spreaman’s rank order correlation between
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FIG. 3. Presentation order and pattern goodness. The effects of the order of presentation and pattern goodness on recall. Gp = “good” pattern; Go = “good” order; Rp = random pattern; Ro = random order (percentages of correctly recalled locations).
the ease of naming and the probability of recall was as low (p = 0.01) and not significant. Therefore, no superiority based on naming could be shown. Error distributions in this experiment are very similar to those in Experiment 1. The distribution of adjacency errors among the 362 errors of commission have been presented in Table 2 (top). The adjacency superTABLE 2 Adjacent and Non-adjacent Location Errors (Top) and Continuous and Discontinuous Location Errors (Bottom Panel)
GG
GR
RG
RR
Total
Adjacent Non-adjacent Total
13 2 15
14 1 15
34 4 38
26 4 28
87 11 100
Continuous Discontinuous Total
12 1 13
12 6 18
15 11 26
27 14 41
66 32 100
Percentages of all errors of commission
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iority is clear but not as strong as in Experiment 1. Again, the majority of adjacency errors are committed in recalling random forms. The continuity vs. discontinuity errors also have a very similar distribution to those in Experiment 1 (see Table 2, bottom panel). The error distributions are to a large extent similar to those in Experiment 1 and provide no new conclusions. The inferiority of random presentation order suggests that subjects keep the dots in working memory for some time before they are able to integrate them with the other dots. The Gestalt principles of closure, symmetry, proximity, etc. are used in constructing images with sufficient detail. The strong interaction supports this interpretation. The use of Gestalt principles in constructing visuo-spatial representation can thus be interfered with in two ways: either by randomizing the pattern or randomizing the order of presentation. The randomization of the shape makes the use of Gestalt principles very difficult; as there is no global shape to build on the image, there are only small and incidental well-shaped subpatterns. The randomization of presentation has quite different effects. It makes it necessary for the subjects to keep in working memory singly “floating” dots, which can be associated or chunked with others only in a later stage of presentation, when a sufficient number of dots has been read and suitable associates can be found. The interaction between conditions suggests that subjects benefit in encoding “good” forms from “good” presentation order. It allows them better opportunity to build chunks than random order in which some of the key dots may be lost and, consequently, the construction of the “good” form may be impaired. This fact provides further support for the Gestalt interpretation.
EXPERIMENT 3 Stimuli with “good” form are sometimes reminiscent of a familiar perceptual form, e.g. a diamond. Though not all the stimuli have a nameable form and no nameability superiority can be shown in post hoc tests, it may be that subjects are able to give names for some subfigures, and they may be better at this with “good” forms than with random forms. Therefore, there is still a slight possibility that subjects retain the stimuli better with a nameable pattern or subpattern, and the results would therefore reflect, rather, the ease of recalling a familiar name than encoding the Gestalt of a pattern. The most evident argument against the above thesis is the fact that subjects must first have an image of the pattern before they can name it. Further, it can be argued that subjects must recall the locations of the pieces, and an overall verbal knowledge about the form does not entail
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knowledge about the locations. A diamond, for example, can be either large or small. It can also be transferred one square left or right from where it actually is, and the knowledge of the name of a familiar form cannot entail the precise location of the pattern, which is the decisive task demand. The counter-argument can and must also be studied empirically. It can be argued that some functional use of the patterns-eg. their rotationwould have a much greater effect on random patterns than it has on verbally labelled patterns. A rotated diamond is still a diamond, and therefore “good” patterns, if verbal labelling is decisive for their maintenance, should not suffer from the rotation.
Method Subjects. Ten subjects participated in the experiment. They were recruited in the same way as the subjects in the first two experiments. Stimuli and Procedure. The same set of 20 stimuli was used as in the previous experiments. The procedure was otherwise similar to the two previous experiments, but subjects were asked in half of the stimuli to rotate them 90”before recall. The order of rotated and non-rotated stimuli was randomized, but the presentation order was regularly from left to right, in both “good” and scattered patterns.
Result and Discussion The randomized stimuli were again less well recalled than those with a “good” shape. The difference was around 40% and was statistically significant, F(1, 9) = 93.60, p < 0.001 (see Figure 4). The third experiment thus confirms the results of the previous experiments. “Good” patterns are better recalled, even though the presentation was auditory, and thus the direct use of percept organization would be impossible. Rotation also proved to be an impairing factor. The stimuli to be rotated were substantially less well recalled than the non-rotated ones, and the difference was statistically significant, F(1, 9) = 21.22, p < 0.001. The interaction, however, was not significant [F(1, 9) = 0.331. The results suggest that rotation affects encoding. The analysis of a total of 726 errors of commission made by the subjects did not introduce much new information. The adjacency errors are presented in Table 3 (top panel). In Table 3 the adjacenthon-adjacent relations remain normal. However, the rotated stimuli are somewhat more prone to adjacency errors. So the rotation may cause some difficulties for subjects when they try to define the locations precisely. The distribution of continuous vs. discontinuous errors reflects the normal pattern of these
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FIG. 4. Rotation and pattern goodness. Rotation and pattern goodness. Gnrot = “good” pattern, no rotation; Grot = ‘‘good’’ pattern rotated; Rnrot = random pattern, no rotation; Rrot = random pattern rotated (percentages of correctly recalled locations).
TABLE 3 Adjacent and Non-adjacent Location Errors (Top) and Continuous and Discontinuous Location Errors (Bottom Panel)
G
GR
R
RR
Total
Adjacent Non- adjacent Total
11 1
22
32 4
93 8
12
23
28 2 30
36
100
Continuous Discontinuous Total
9 2
22 23
29 7 36
85
11
25 4 29
1
1
Percentages of all errors of commission.
412
14 100
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errors (see Table 3, bottom panel). If the relatively high interference caused by rotation in recalling good patterns is excluded, there is nothing special in the results compared with Experiments 1 and 2. The results do not provide evidence for the importance of verbal labelling. The loss of information is roughly equivalent in “good” and random stimuli. Therefore, the benefit subjects possibly have from using verbal labelling does not help them against the interference caused by mental rotation. It means that the “good” form superiority is caused by pictorial or conceptual rather than verbal factors.
EXPERIMENT 4 An important property of “good” forms is that they can be easily distinguished from their background, if the background has a random form. If the effect of the good “Gestalts” is really perceptual, one should be able to benefit from the good forms compared to random forms, even though both had been embedded in the same stimulus. In this experiment the recall of “pure” “good” and random patterns are compared with the retention of “good” and random patterns embedded in the same stimulus. The embedding of “good” forms or their fragments and the randomization of the background should also cause “perceptual” competition and therefore impair the recall of the “good” forms. In this way the experiments should provide a new type of evidence for the sharing of processing resources between images and percepts.
Method Subjects. Twelve first-year psychology students participated to the experiment. They were given a course credit for their participation. Stimuli. Eighteen dot matrixes were read onto a tape. None of the good or totally randomized patterns had been used in the previous experiments. In six of the dot matrixes there were 14-15 dots forming a “good” pattern (Good Forms); in another six the dots formed a random pattern (Rand. Forms); in the remaining six half of the dots belonged to a “good” form (Good Parts) and the other half was randomized (Rand. Parts). These stimuli were made by randomizing half of the points in some of the patterns used in the previous three experiments. Procedure. The procedure was the same as in the previous experiments.
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Results and Discussion The experiment replicated the previous good vs. random pattern effects. The overall differences between conditions were significant, F(3, 33) = 51.38,p < 0.001.Comparison of individual means with Duncan’s multiple range test showed that “good” patterns were recalled substantially better than random patterns (CR = 13.64,p < 0.001). The difference between “good” and random parts was also significant (CR = 7.22, p < 0.05) as well as the differences between random stimuli and random parts and good stimuli and “good” parts (CR = 7.22, p < 0.05). The error distribution was very similar to the previous experiments. Adjacent and continuous errors of commission are clearly more frequent than non-adjacent or discontinuous errors in the total of 509 errors. In Table 4, “good” part vs. random part comparisons have not been made, as it is not possible to ascertain, say with an error of commission, to which part of a stimulus it belongs. Again, the majority of errors are adjacent errors-i.e. subjects put a piece into a wrong cell next to a correct location. Though the number of non-adjacent cells is smaller than the number of adjacent cells, the distribu-
FIG. 5. Embedded good patterns. The results of the fourth experiment (percentages of correctly recalled dot locations).
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TABLE 4 Adjacent and Non-adjacent Location Errors (Top) and Continuous and Discontinuous Location Errors (Bottom Panel)
G
HR
R
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Adjacent Non-adjacent Total
10
38 1 39
47
95 3 100
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tion is far too biased to be caused purely by random guessing. Obviously, subjects have some idea about the correct location, but they fail to encode it precisely. The same phenomenon has also been found in experiments on chess players (Chase & Simon, 1973). The degree of randomness increases the number of probability or adjacency errors. This suggests that good Gestalt helps subjects in locating the dots precisely. This is naturally associated with the ease of recall. A high percentage of correct recalls decreases the probability of errors. Contiguity errors are more common than discontinuous errors. Subjects are more apt to “guess” a location that is next to an already existing group of pieces than a location that is separate. If the two types of errors are viewed as a whole, it seems that subjects do not make blind guesses. They like to group pieces into larger continuous chunks, or if they recall single pieces, they do it because they have a rough idea about the correct location. The results show that subjects are fully able to extract good forms from auditorily presented stimuli and benefit from them, even though they were embedded among random dots, but the performance was never as successful as in the recall of “pure” good patterns. Subjects were also better able to recall the random dots in half-randomized matrixes compared to the totally randomized matrixes. This suggests that the subjects relied on “good” forms to support the encoding of random forms. They constructed illusory “good” patterns by associating random dots with the fragments of “good” patterns. The selection of a “good” pattern is thus not an absolutely determined process. When there is a random background, subjects are able to construct alternative chunks. They may in this way lose some dots in good fragments, but this can be compensated by the corresponding rise in the recall of randomized dots.
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GENERAL DISCUSSION In all four experiments “good” patterns were more successfully recalled than scattered ones. The order of presentation, the speed of presentation, and the rotation of stimuli impair the level of performance. The impairment is in the first case larger with “good” forms than with random but roughly equal in the latter case. The last experiment also showed that subjects are able to use fragments of “good” forms and to some extent associate random background dots with them, which means that they are to some degree able to select among the alternative interpretations. No naming effect could be shown, but the adjacency and continuity properties of the errors of commission proved to be strong. The data support the main hypothesis. Subjects benefit from the “good” visual organization of stimulus patterns, despite the fact that the patterns are presented auditorily. The processing resources used in the Gestalt organization of visual percepts are also used in processing visual images, and therefore the resources used in perceptual organization are shared to some degree with the resources used in constructing visuo-spatial representations from auditory inputs. The speed of presentation effect is logical. It is well known that images have a construction time, and therefore the increase in the speed of presentation decreases the number of recalled pieces (Kosslyn, 1980). The order of presentation effect can be explained in terms of visual information chunking. The randomized order of presentation impairs recall, as it impairs the use of some Gestalt principles such as proximity. In randomized presentation subjects must keep floating dots or dot groups much longer in the working memory before they are able to find the closest associates and build suitable chunks. The nameability of forms does not seem to have any important role. Perhaps this is due to the fact that subjects must first be able to form the image before they are able to name it. As only one object is used per stimulus, the familiarity of the names cannot greatly aid the storage and retention of the stimuli. Experiment 4 showed that subjects may construct alternative representations. They are able to associate random dots with fragments of “good” forms. This suggests that they may use some perceptual-like selection in encoding random positions. The stimuli in the experiments were auditory. They did not contain any visual Gestalt properties; however, visually “good” forms were recalled much better than random ones. Undoubtedly, subjects have first translated the verbal stimuli into propositional format in order to understand them. The major problem is, however, how the Gestalt properties are obtained. The theoreticians are surprisingly unanimous on the Gestalt-related questions. The grouping processes responsible for Gestalt properties are
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usually assumed to take place at a very early stage. Marr (1982) suggested that Gestalt properties are encoded in the construction of primal sketch (Marr, 1982). Accordingly, Pylyshyn (1978) argues that Gestalt properties are encoded by a “transputer”, which is responsible for transforming physical energy into symbol structures. This “transputer” he assumed to be excluded from the process of imaging, though the results of transputing can be stored in long-term memory. Kosslyn (1991) argues that Gestalt properties are encoded at early processing state in visual buffer. Kosslyn (1991), differently from Pylyshyn (1978), assumes that perceptual learning can take place in the early stage of processing. Kosslyn (1991) assumes also a pattern activation subsystem, in which visual patterns are stored. These patterns correspond to shapes of objects or parts of objects. The perceptual Gestalt grouping is assumed to have its origin in an early phase of visual processing. With respect to the current results, this would mean that auditory stimuli should have access to the processing resources responsible for early visual stimulus processing. However, the access to earliest perceptual stimulus coding can hardly be the right explanation. It would be in contradiction with the bottom-up processing assumption. A problem with this explanation is also the sufficiency of Gestalt properties. This means that the Gestalt properties can provide the form of a representation but not their content. In the case of percept the issue is simple, because physical stimulus information provides the objects, but when the presentation is auditory, the origin of objects is unclear. Consequently, I prefer to search for some other origin of the “good” form superiority rather than visual buffer processing. Pattern memory provides an alternative explanation to the visual buffer. The verbal stimuli could activate a number of patterns, and these activated patterns might be used in the construction of the final representation. This kind of procedure would be very similar to what happens in chess players’ recall of auditorily presented chess positions and games (Saariluoma, 1989, 1991b). Chess players transform verbal knowledge into visuo-spatial images using their pre-learned chess-specific patterns. The pattern construction view can be supported by the results. Subjects made a substantial number of errors. They forgot totally or dislocated slightly parts of the stimulus patterns, which suggests that they constructed the final representation of elementary parts and did not encode it as a single whole. If they had a clear idea of the total “Gestalt” of a stimulus, they would dislocate not only some of the parts, but the whole. The randomization of reading order impaired subjects’ performance, but it did not totally destroy the representation. It made subjects lose some of the patterns, but not all. This phenomenon also supports part-by-part encoding. In Experiment 4 the subjects actively used random dots and
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associated them into “good” parts. However, it is far from clear whether the random dots could be in harmony with the parts of one single “Gestalt” or only with the parts with which they were associated. The above arguments suggest that the origin of representation is in some pattern activation subsystem or some other visual pattern storage rather than in the early visual processing systems. According to this alternative “good” form superiority is based on the “good” form of the stored patterns and not on the early physical stimulus encoding. Also, it is logical to assume that propositional information can be better used to obtain information from the pattern activation subsystem than from visual buffer (Kosslyn, 1991). Finally, one may ask whether visual images share Gestalt properties with percepts. The answer seems to be yes in so far as pattern storage is concerned, because pattern-activation-storage-type memories are run topdown and bottom-up. It is not possible that our percepts would not be automatically enriched by the pattern information. On the other hand, pattern storage is also used to construct images with or without the immediate presence of the object. In fact, we very probably use this storage to build up images of objects that do not exist, such as centaurs. Therefore, the “output” of the pattern storage is not always a percept. Subsequently, a tentative answer to the main question could be that images and percepts share Gestalt properties, but only through the pre-learned pattern information.
REFERENCES Asch, S., Ceraso. J., & Heimer, W. (1960). Perceptual conditions of association. Psychological Monographs, 74, 1 4 8 . Baddeley, A.D. (1986). Working memory. Cambridge: Cambridge University Press. Baddeley, A.D. (1988). Imagery and working memory. In M. Denis, J. Engelkamp & J . Richardson (Eds.), Cognitive and neuropsychological approaches to mental imagery. Dordrecht: Martinus Nijhoff. Baddeley. A., & Hitch, G. (1974). Working memory. In G. Bower (Ed.), The psychology of learning and motivation, Vol. 8 . New York: Academic Press. Bradley, A., Hudson, S., Robbins, T.. & Baddeley, A. (1987). Working memory and chess (Unpublished report, Cambridge, May 1987). Bundesen, C., & Larsen, A. (1975). Visual transformation of size. Journal of Experimental Psychology: Human Perception and Performance, 3, 214-220. Chase, W.G., & Simon, H.A. (1973). The mind’s eye in chess. In W.G.Chase (Ed.), Visual information processing (pp. 215-281). New York: Academic Press. Cooper, L., & Shepard, R. (1973). Chronometric studies of the rotation of mental images. In W. Chase (Ed.), Visual information processing. New York: Academic Press. Denis, M. (1982). Images and semantic representations. In J.-F. Le Ny & W. Kintsch (Eds.), Language and comprehension. Amsterdam: North-Holland. Farah, M. (1985). Psychophysical evidence for a shared representational medium for mental images. Journal of Experimental Psychology: General, 114,91-103.
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Farah, M. (1988). Is visual imagery really visual? Overlooked evidence from neuropsychology. Psychological Review, 3, 307-317. Farah, M.J.. & Smith, A.F. (1983). Perceptual interference and facilitation with auditory imagery. Perception & Psychophysics, 33, 475-478. Finke, R.A. (1980). Levels of equivalence in imagery and perception. Psychological Review, 87, 113-132. Finke, R. (1985). Theories relating mental imagery to perception. Psychological Bulletin, 98, 236-259. Garner, W.R. (1974). The processing of information and structure. Hillsdale, NJ: Lawrence Erlbaum Associates, Inc. Harber, R.N. (1979). Twenty years of haunting eidetic imagery: Where is the ghost? The Behavioural and Brain Sciences, 2, 583-629. Kosslyn, S. (1980). Image and mind. Cambridge, MA: Harvard University Press. Kosslyn, S.M. (1987). Seeing and imagining in the cerebral hemispheres: A computing approach. Psychological Review, 94. 148-175. Kosslyn, S.M. (1991). A cognitive neuroscience of visual cognition: Further developments. In R.H. Logie & M. Denis (Eds.), Mental images in human cognition. Amsterdam: North Holland. Kohler, W. (1935). Gestalt psychology. New York: Harbinger. Lasaga, M.L. (1989). Gestalts and their components: Nature of information-precedence. In B.E. Shepp & S. Ballesteros (Eds.). Object perception: Structure and process (pp. 165202). Hillsdale, NJ: Lawrence Erlbaum Associates, Inc. Logie, R.H. (1986). Visuo-spatial processing in working memory. The Quarterly Journal of Experimental Psychology, 38A. 229-247. Marr, D. (1982). Vision. San Francisco, CA: Freeman. Paivio, A. (1971). Imagery and verbal processes. New York: Holt. Paivio, A. (1978). Comparison of mental clocks. Journal of Experimental Psychology: Human Perception and Performance, 4. Paivio, A. (1986). Mental representations: A dual coding approach. Oxford: Oxford University Press. Pylyshyn, Z.W. (1978). Imagery and artificial intelligence. In C.W. Sawage (Ed.). Perception and cognition: Issues in the foundations of psychology. Minnesota Studies in the Philosophy of Science, Vol. 9. Minneapolis, MN: University of Minneapolis Press. Richardson, A. (1969). Mental imagery. New York: Springer. Richardson, J. (1980). Mental imagery and human memory. London: McMillan. Saariluoma, P. (1989). Chess players' recall of auditorily presented chess positions. European Journal of Cognitive Psychology. I, 309-320. Saariluoma, P. (1991a). Visuo-spatial interference and apperception in chess. In R.H. Logie & M. Denis (Eds.), Mental images in human cognition. Amsterdam: North Holland. Saariluoma, P. (1991b). Aspects of skilled imagery in blindfold chess. Acta fsychologica, 77, 65-89. Saariluoma, P. (1992). Visuo-spatial and articulatory interference in chess players' information intake. Applied Cognitive Psychology, 6. 77-89. Segal, S., & Fusella, V. (1970). Influence of imaged pictures and sounds on detection of visual and auditory signals. Journal of Experimental Psychology, 83, 458-463. Shepatd, R., & Metzler, J. (1971). Mental rotation of three-dimensional objects. Science, 171, 701-703. Wertheimer. M. (1923). Laws of organization in perceptual forms. In W. Ellis (Ed.), A source book of Gestalt psychology. London: Routledge & Kegal Paul.
Revised manuscript received I 1 April 1992
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APPENDIX Non-nameable and Nameable Patterns from Experiments 1 and 2 and the Percentage of Subjects Who Have Classified a Particular Pattern Easy to Name
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ISSN: 0272-4987 (Print) 1464-0740 (Online) Journal homepage: http://www.tandfonline.com/loi/pqja20
Do visual images have gestalt properties? Pertti Saariluoma To cite this article: Pertti Saariluoma (1992) Do visual images have gestalt properties?, The Quarterly Journal of Experimental Psychology Section A, 45:3, 399-420, DOI: 10.1080/02724989208250621 To link to this article: http://dx.doi.org/10.1080/02724989208250621
Published online: 29 May 2007.
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Date: 01 June 2016, At: 13:10
THE QUARTERLY JOURNAL OF EXPERIMENTAL PSYCHOLOGY, 1992,45A (3) 3 W 2 0
Do Visual Images have Gestalt Properties? Pertti Saariluoma
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University of Helsinki, Finland
Recent research has demonstrated that percepts and images share processing resources. A natural consequence of this evidence is to ask what kind of properties are shared by the two representational systems, i.e. images and percepts. To what degree, for example, do images share the complex organization of visual percepts? This paper investigates whether percepts and images share Gestalt properties. Four experiments were conducted to study this hypothesis. In all experiments subjects were presented with an auditory message in which approximately 15 locations in a matrix were defined by giving the co-ordinates of the cells. Half of the stimuli presented some “good” form, whereas in the other half the locations of the pieces were scattered. Subjects were systematically less able to recall the locations of the random forms. Therefore, it could be argued that the “good” forms help in image construction, even though the elements were auditorily presented. Effects of varying presentation speed, order, and of requiring a mental rotation before recall support this conclusion,
Consistent evidence has been found for the overlapping cognitive and neural processing resources of visual images and percepts (Farah, 1985; Finke, 1980,1985;Kosslyn, 1987). The most obvious evidence is the experience of images. They are reported to be more like percepts than stories. Thus, we are able to recall the colour of a continuous object, though we are unlikely to be able to describe all the points on its surface verbally. The experience of an image is not, of course, sufficient argument for shared processing resources, but the number of objective observations that supRequests for reprints should be sent to Pertti Saariluoma, Department of Psychology, University of Helsinki, Fabianinkatu 28, 00100 Helsinki 10, Finland. I am very grateful to Robert H. Logie and an unknown referee for their helpful comments and suggestions. I would also like to thank Lauri Oksama, Tiina Takala, and Michael Miettinen for running the experiments and Mark Shackleton, Lecturer in English at the University of Helsinki, for correcting the language. The research has been supported by the Academy of Finland. @ 1992 The Experimental Psychology Society
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port overlapping resources has grown substantially during the last ten to fifteen years or so (Farah, 1988; Finke, 1985). Consequently, it is now fairly safe to assume the existence of shared processing resources and to try to define precisely the overlapping parts of the percepts and images. An argument for the shared processing resources for images and percepts is the high percept-like character of some forms of images such as eidetic images. This form of imagery is so vivid and close to percepts that eidetic images have sometimes been called “photographic memories” (Richardson, 1969). This phenomenon appears to be virtually decisive evidence in support of shared processing resources. However, only a small part of the population can produce eidetic images, and therefore eidetic images can hardly be taken as a crucial argument for shared representational resources between images and percepts (Harber, 1979). It may only be argued that the existence of the phenomenon could hardly be possible without any connections between percepts and images. Stronger evidence can be found in image-percept interference and interaction experiments, which show that mental images and visual percepts interfere with each other. A classic experiment by Segal and Fusella (1970) showed that image interference in detecting perceptual stimuli is larger in isomodal than cross-modal conditions. It has later also been shown that images may cause selective facilitation in the perception of a stimulus. Farah and Smith (1983), for example, have shown that auditory images may facilitate perception of the same frequency signals. The contradictory findings suggest that percepts and images may interact and share the representational resources. A very clear example of imaging interference effects can be found in experiments on visual working memory (Baddeley, 1986; Baddeley & Hitch, 1974). Visuo-spatial secondary tasks usually strongly interfere with visual-memory and imagery tasks (Baddeley, 1986, 1988). Even unattended pictorial material may cause some processes to deteriorate. As Logie (1986) showed, unattended pictures interfere with the use of imagery-based mnemonics. Numerous experiments demonstrate the solidity of imaging interference on the processing of visuo-spatial materials. Even experts in a field suffer from imaging interference. Bradley, Hudson, Robbins, and Baddeley (1987) found a strong imaging interference effect in chess players’ recall of chess positions. Similarly, Saariluoma (1991a, 1992) has shown that chess players’ calculation of variations suffers from imaging interference. A third link between images and percepts is to be seen in functional imagery experiments. Mental rotation, transformation of size, image overflow, scanning, and comparison of imagined objects all show effects that are highly analogous with the physical manipulation of the same objects (Bundesen & Larsen, 1975; Kosslyn, 1980; Cooper & Shepard, 1973;
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Shepard & Metzler, 1971). Paivio (1978), for example, asked subjects to select from two clock times the one in which the angular distance between the hands was smaller and found that the comparison reaction time increased as the difference decreased. Similar differences were found with pictures of clocks. An extensive literature also shows that concrete, i.e. visible, objects and their names can be recalled better than abstract objects, i.e. objects that are not highly visible (Paivio, 1971, 1986). Additionally, if the subjects are able to form an image of a word that is close to a percept, it is more likely that they will recall it than a case where the word is somewhat abstract (Paivio, 1971, 1986; Richardson, 1980). This also suggests that percepts and images are close to each other. Finally, Farah (1988) has presented strong neuropsychological evidence for a shared representational medium for images and percepts. Though the above-mentioned lines of research provide clear evidence for shared representations, none of them suggests total overlap. If images and percepts do not share all the processing resources, it must be asked to what degree overlap does exist. In addition, which properties of visual percepts are important in processing images, and which are not? A very evident property of percepts that could be compared with images is their high level of organization. Do images share some organizational aspects with percepts? Do images have, for example, Gestalt properties? The latter question is the main topic of this paper. Gestalt psychologists have shown how the human perceptual system is able to organize meaningless patterns of lines and dots into “meaningful” wholes by using relatively simple principles, such as similarity, symmetry, proximity, good continuation, etc. (Lasaga, 1989; Kohler, 1935; Wertheimer, 1923). If images and percepts do share processing resources, a very interesting question arises, namely, whether people also use the same principles of good organization in constructing images that they use in constructing percepts. Memory experiments with dot matrixes and some meaningless forms show that a good Gestalt improves the recall of visual patterns (Asch, Ceraso, & Heimer, 1960; Garner, 1974). This suggests that visual images share Gestalt properties with visual images. Unfortunately, the experiments with visually presented stimuli cannot provide unambiguous evidence for the sharing of organizational resources, because the stimuli have first been encoded visually, and therefore the origin of organization may be on the visual rather than the imagery level. Subjects might simply be able to benefit from “good forms” because they have stored the visual trace information in their long-term memory. It might be that they could not encode the “good” forms unless the shapes had been first processed by the resources responsible for the visual but not the imagery processing.
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On the other hand, people use mental images and benefit from them in encoding verbal materials. People with vivid visual images understand prose better than less vivid imagers (see Denis, 1982). It is also known that people often use visuo-spatial working memory for encoding and storing verbal information (Baddeley, 1986). Saariluoma (1991b), for example, presented chess positions auditorily for recall to chess players to test recall and found a strong concurrent imaging interference effect, although articulatory performance level was well over 90% with skilled chess players. Therefore, it may be assumed that subjects’ mental images can be studied by representing auditorily a task whose basic task demands are spatial. Consequently, in the present experiments the mode of stimulus representation was changed compared to earlier experiments on Gestalt effects in recall. Instead of presenting the patterns to be recalled visually, they were presented auditorily. The locations to be recalled were specified by verbally giving the x and y co-ordinates of an imaginary matrix. It was assumed that if subjects could still benefit from the “good” forms of presented groups of dots, it is a sign that images share some organizational properties with percepts. As the pattern “goodness” was varied in the Gestalt sense, the organizational properties should be the Gestalt properties of the stimuli. It is important for our concept of image if it can be shown that subjects are better able to recall “good” forms than random ones, because Gestalt properties are usually thought to be encoded at a very early stage of processing (Kosslyn, 1991; Marr, 1982; Pylyshyn, 1978). Verbally presented propositions cannot have any visual Gestalt properties themselves, and they must be added into representation by the processing system. If images really do have Gestalt properties and their origin can be found, it will undoubtedly increase our understanding of images and the mechanisms of “Gestalts”.
GENERAL METHOD In all experiments subjects were asked to recall the locations of a set of 14 to 15 dots “placed” on an imaginary 8 X 8 matrix. The locations of the dots were read to them using a tape recorder. The location of each dot was specified by using a chessboard- or spreadsheet-type notational system: a cell in the matrix was specified by reading its co-ordinates, one of which was a letter (a-h) and the other a number (1-8). The expression “al” specified, therefore, one cell, and “a2” or “bl” two of its adjacent cells. The matrix on which the dots were recalled was visible for the subjects during the presentation, but they were only allowed to put pieces on it after all the dots had been read out from the tape. Therefore, they had to
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FIG. 1. Four examples of stimuli: two good and two random forms.
construct the locations of objects in their mental image. Two examples of “good” and “random” forms are presented in Figure 1. It was assumed that each cell read out contained a dot, and the subjects were asked to recall as many dots as possible immediately after the presentation was over. Recall was made by placing black draughts pieces, referred to here as dots, on the verbally specified squares on a real board. The number of correctly placed pieces was scored, and the results present the average percentage of correctly placed dots per stimulus position. The forms of dot groups were manipulated either by letting them form some “good” shape such as a square, symmetrical rows, a triangle, the letter Z, and so on, or by scattering the locations randomly. If subjects are able to use Gestalt properties of images in encoding the auditory messages, they should be substantially better in recalling good forms than in recalling random forms.
EXPERIMENT 1 The main interest of this experiment was whether the subjects could benefit from the “good” Gestalt of the well-organized dot patterns, though the presentation was auditory and they could not, therefore, use their visual system in stimulus organization. A positive answer to the question would provide prima facie evidence for shared organizational resources. Another question the experiment was designed to answer was the effect of the speed of presentation. Saariluoma (1989) has shown that chess players’ recall of auditorily presented chess positions suffers from a faster speed of presentation, even though this does not cause any qualitative effects. The reading was varied in this experiment in order to find a suitable speed.
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Method
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Subjects. Eight subjects were used; they were first-year psychology students at the University of Helsinki, and they were given a course credit for their participation. Stimuli. Twenty dot matrixes were read onto a tape. In half of them the dots formed a “good” pattern (Kohler, 1935), in the other half, the dots were scattered in the matrix. The locations of the dots were read onto a tape either at a speed of one location per second or one location every two seconds. They were read out from left to right, from top to bottom. In this way four sets of five stimuli were acquired: “good” form at one dot per sec, random form at one dot per sec, “good” form at one dot every 2 sec, and random form at one dot every 2 sec. To control the possible differences between the read positions, a second tape was made in which the stimuli that had been read at the speed of one dot per sec were read at the speed of one dot every 2 sec and vice versa. Half of the subjects were presented with the first tape and the other half with the second tape.
Procedure. The stimuli were presented to the subjects in randomized order. Subjects heard one set of stimuli-i.e. one array-at a time, and they were required to recall all the dots in that array immediately after they had heard the location of the last dot. Therefore, they had to rely on their image of the locations. Recall was made by placing round draughts pieces on a white matrix of cells.
Results and Discussion The results of the experiments are presented in Figure 2. For clarity, the means of “good” vs. random shape and presentation time 1 vs. 2 sec have been presented separately. The differences between “good” vs. random shape comparisons are very clear, the absolute difference in means being almost 40%. The difference is statistically significant, F(1, 7) = 139.7, p < 0.001. The results of the first experiment thus support the main hypothesis. Though the presentation is auditory, subjects benefit from “good” forms. To recall the dot locations, subjects form an image of the matrix, and they locate the dots on that image. If the shape of a pattern is “good”, they can chunk it, as a good chess player can chunk chess-specific patterns, more easily and store it in long-term memory (Saariluoma, 1989). The speed of reading effect is quite large and statistically significant, F(1, 7) = 26.46, p < 0.001. There was no significant interaction between the conditions. Presumably, the speed of reading effect is caused by the
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FIG. 2. Time and pattern goodness. The effects of time and presentation order on recall. Goodl = “good” pattern, one sec; Good2 = “good” pattern, two sec; Random1 = randomized pattern, one sec; Random2 = randomized pattern, two sec (percentages of correctly recalled locations).
time it takes to form a visuo-spatial representation. Subjects lose dots because they have not yet been able to encode adequately the previously presented dots. The increased speed causes an overflow in image construction. This overflow, however, is roughly the same in both conditions, and the interaction between conditions was not significant [F(l, 7) = 2.891. An important question is the possible influence of verbal labels on recall. The literature cited in the introduction suggests that subjects may better recall “good” forms that are easy to name than “good” forms that are difficult to name. This issue can be studied in a post hoc manner by dividing the “good” stimuli into two equally large groups: easily nameable items (e.g. diamond, cross) and very difficult or non-nameable items (see Appendix). A group of ten subjects were asked to classify the “good” stimuli into difficult and easily nameable ones. The absolute number of classifications into easily nameable category was taken as the measure of the ease of nameability. When this nameability measure was correlated with the recall probability of the stimuli using Spearman’s rank correlation, no dependency could be found (p = 0.07, n.s.).
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Subjects regularly made errors of commission, and these errors provide further information about the cognitive mechanisms behind subjects’ “good” Gestalt superiority. These errors can be looked at from two different points of view: (1) it is possible to compare the location of an erroneous dot with the presented stimulus, and (2) it is possible to compare it with the recalled dots. To study the first aspect of the errors, they were allocated two two classes: in one class were put all the errors in which subjects had placed a piece into a cell next to some actually existing piece, in the other class all the pieces that were not immediately adjacent to some piece read to the subjects. The errors belonging to the first class were termed adjacent errors and the errors in the latter class non-adjacent errors. The adjacent vs. non-adjacent classification may be assumed to provide information about the blindness of guessing. If the pieces are located close to correct locations, it suggests that subjects have had some idea about the location of the dot. If the errors of commission are spread randomly over the board, they are caused by blind guessing. In the first experiment the results were clearly biased towards adjacency errors in all four conditions. The percentages of the eight types of errors of all 344 errors of commission are presented in Table 1 (top). Subjects make surprisingly large numbers of adjacency errors. They are more probable, but this cannot be explained solely on the basis of random guessing. The probability of putting a piece randomly on a non-adjacent square is 0.25 and to an adjacent square 0.52 with “good” formed positions. With random positions the corresponding probabilities are 0.12 and 0.64. However, in “good” positions adjacent errors are approximately 40 times more common than non-adjacent, and even in random positions the empirical probability is 12 to 27 times larger. The empirical ratios are clearly TABLE 1 Adjacent and Non-adjacent Location Errors (Top) and Continuous and Discontinuous Location Errors (Bottom Panel)
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42 1 43
96 3 100
Continuous Discontinuous Total
12 3 15
15 12 27
12 3 15
31 12 43
70 30 100
Percentages of all errors of commission.
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larger (2-3 times) than one would expect on the basis of expected probabilities. This suggests that in making an error of commission a subject has some overall idea about the location of the dot, but he or she has not been able to encode it precisely. The other classification of the errors of commission is based on their relation to recalled dots, real or imaginary. If a dot is located erroneously next to some other recalled dot, it is a continuity error. If no dots are placed in cells adjacent to it, it is classified as a discontinuous error. The continuity properties of errors are assumed to provide information about the Gestalt properties of the recalled form. It may be argued that a dot that is placed next to some other shares a “good continuity” or proximity property with the other dot. So the probability with which subjects place a piece erroneously next to another piece may provide information about the chunking mechanisms subjects use in these kinds of tasks. The distribution of errors in eight main conditions has been presented in Table 1 (bottom). The distribution is quite similar to that shown in the top panel in Table 1, although the continuouddiscontinuous difference in Table 1 is smaller than the corresponding adjacenthon-adjacent difference, and the “good” vs. “random” pattern asymmetry is somewhat smaller. The superiority of continuous over discontinuous errors suggests that subjects try to encode larger wholes than just single pieces. However, they may often fail in locating their chunks precisely. The results support the claim that subjects use and benefit from some Gestalt principles in representing auditorily presented dot groups. “Good” pattern superiority is very clear, and there is no evidence for the assumption that it is caused by naming. The analysis of errors also shows that continuity and adjacency errors are frequent. This suggests that the errors of commission are not caused by blind guessing but reflect rather chunking mechanisms. Subjects often rely on an overall impression of the dot locations, and they also use continuity properties of dot groups. An interesting problem is, of course, why subjects make more commission errors with random stimuli if these errors are caused by chunks, which are partly made by using Gestalt principles. The explanation is that the subjects are also able to extract such chunks in random positions. The size of these chunks is just substantially smaller.
EXPERIMENT 2 Though the first experiment provided evidence for the use of Gestalt principles in constructing mental images, it may be thought that the order of the presentation of the dots with scattered patterns may be more random with random than with “good” patterns. One might think, for example, that the dots in “good” forms are somehow more regular when read from
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left to right than are the scattered patterns. Therefore, it might be that the difference between random and “good” forms is due to the organization of the presented dot sequences ’and has nothing to do with the images themselves. To study possible sequence order effects in “good” pattern superiority the order of presentation was varied. If “good” pattern superiority disappears when the dot sequences are presented in random order and not from left to right, it can be argued that the difference between “good” and random forms was not caused by imagery level effects but rather by the difficulties in organizing the encoding of scattered patterns into propositions.
Method Subjects. Eight subjects participated in the experiment. They were all students from an elementary course in psychology, and they received a course credit for participating in the experiment. Stimuli. The same dot patterns were used as in the previous experiment; the only difference was that instead of varying the reading speed, the reading order was varied. In ordered reading five “good” forms and five random dot patterns were presented at the speed of one dot every 2 sec starting from left and proceeding to the right. In random reading order five “good” and five random forms were presented, so that the presentation order of dots was not regular but random. Again two complementary tapes were used. Procedure. The procedure was the same as in the first experiment.
Results and Discussion Reading order is an important factor. The random order substantially decreases the performance level; the difference is large and statistically significant, F(1, 7) = 74.72, p < 0.001. A randomized presentation order clearly impairs recall of the dot patterns (Figure 3). However, the results do not support the critical hypothesis. Not only “good” patterns suffer from the randomized presentation order; the recall of random patterns is evidently impaired by the randomized presentation, F(1, 7) = 50.55, p < 0.001, though the interaction is clear, F(1, 7) = 13.36, p < 0.001. The results of the previous experiment were thus not accidental for a “good” shape makes it easier to build a visuo-spatial representation of auditorily presented sets of dots. The comparison between easy-to-name and difficult-to-name stimuli provided no new information. Spreaman’s rank order correlation between
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FIG. 3. Presentation order and pattern goodness. The effects of the order of presentation and pattern goodness on recall. Gp = “good” pattern; Go = “good” order; Rp = random pattern; Ro = random order (percentages of correctly recalled locations).
the ease of naming and the probability of recall was as low (p = 0.01) and not significant. Therefore, no superiority based on naming could be shown. Error distributions in this experiment are very similar to those in Experiment 1. The distribution of adjacency errors among the 362 errors of commission have been presented in Table 2 (top). The adjacency superTABLE 2 Adjacent and Non-adjacent Location Errors (Top) and Continuous and Discontinuous Location Errors (Bottom Panel)
GG
GR
RG
RR
Total
Adjacent Non-adjacent Total
13 2 15
14 1 15
34 4 38
26 4 28
87 11 100
Continuous Discontinuous Total
12 1 13
12 6 18
15 11 26
27 14 41
66 32 100
Percentages of all errors of commission
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iority is clear but not as strong as in Experiment 1. Again, the majority of adjacency errors are committed in recalling random forms. The continuity vs. discontinuity errors also have a very similar distribution to those in Experiment 1 (see Table 2, bottom panel). The error distributions are to a large extent similar to those in Experiment 1 and provide no new conclusions. The inferiority of random presentation order suggests that subjects keep the dots in working memory for some time before they are able to integrate them with the other dots. The Gestalt principles of closure, symmetry, proximity, etc. are used in constructing images with sufficient detail. The strong interaction supports this interpretation. The use of Gestalt principles in constructing visuo-spatial representation can thus be interfered with in two ways: either by randomizing the pattern or randomizing the order of presentation. The randomization of the shape makes the use of Gestalt principles very difficult; as there is no global shape to build on the image, there are only small and incidental well-shaped subpatterns. The randomization of presentation has quite different effects. It makes it necessary for the subjects to keep in working memory singly “floating” dots, which can be associated or chunked with others only in a later stage of presentation, when a sufficient number of dots has been read and suitable associates can be found. The interaction between conditions suggests that subjects benefit in encoding “good” forms from “good” presentation order. It allows them better opportunity to build chunks than random order in which some of the key dots may be lost and, consequently, the construction of the “good” form may be impaired. This fact provides further support for the Gestalt interpretation.
EXPERIMENT 3 Stimuli with “good” form are sometimes reminiscent of a familiar perceptual form, e.g. a diamond. Though not all the stimuli have a nameable form and no nameability superiority can be shown in post hoc tests, it may be that subjects are able to give names for some subfigures, and they may be better at this with “good” forms than with random forms. Therefore, there is still a slight possibility that subjects retain the stimuli better with a nameable pattern or subpattern, and the results would therefore reflect, rather, the ease of recalling a familiar name than encoding the Gestalt of a pattern. The most evident argument against the above thesis is the fact that subjects must first have an image of the pattern before they can name it. Further, it can be argued that subjects must recall the locations of the pieces, and an overall verbal knowledge about the form does not entail
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knowledge about the locations. A diamond, for example, can be either large or small. It can also be transferred one square left or right from where it actually is, and the knowledge of the name of a familiar form cannot entail the precise location of the pattern, which is the decisive task demand. The counter-argument can and must also be studied empirically. It can be argued that some functional use of the patterns-eg. their rotationwould have a much greater effect on random patterns than it has on verbally labelled patterns. A rotated diamond is still a diamond, and therefore “good” patterns, if verbal labelling is decisive for their maintenance, should not suffer from the rotation.
Method Subjects. Ten subjects participated in the experiment. They were recruited in the same way as the subjects in the first two experiments. Stimuli and Procedure. The same set of 20 stimuli was used as in the previous experiments. The procedure was otherwise similar to the two previous experiments, but subjects were asked in half of the stimuli to rotate them 90”before recall. The order of rotated and non-rotated stimuli was randomized, but the presentation order was regularly from left to right, in both “good” and scattered patterns.
Result and Discussion The randomized stimuli were again less well recalled than those with a “good” shape. The difference was around 40% and was statistically significant, F(1, 9) = 93.60, p < 0.001 (see Figure 4). The third experiment thus confirms the results of the previous experiments. “Good” patterns are better recalled, even though the presentation was auditory, and thus the direct use of percept organization would be impossible. Rotation also proved to be an impairing factor. The stimuli to be rotated were substantially less well recalled than the non-rotated ones, and the difference was statistically significant, F(1, 9) = 21.22, p < 0.001. The interaction, however, was not significant [F(1, 9) = 0.331. The results suggest that rotation affects encoding. The analysis of a total of 726 errors of commission made by the subjects did not introduce much new information. The adjacency errors are presented in Table 3 (top panel). In Table 3 the adjacenthon-adjacent relations remain normal. However, the rotated stimuli are somewhat more prone to adjacency errors. So the rotation may cause some difficulties for subjects when they try to define the locations precisely. The distribution of continuous vs. discontinuous errors reflects the normal pattern of these
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FIG. 4. Rotation and pattern goodness. Rotation and pattern goodness. Gnrot = “good” pattern, no rotation; Grot = ‘‘good’’ pattern rotated; Rnrot = random pattern, no rotation; Rrot = random pattern rotated (percentages of correctly recalled locations).
TABLE 3 Adjacent and Non-adjacent Location Errors (Top) and Continuous and Discontinuous Location Errors (Bottom Panel)
G
GR
R
RR
Total
Adjacent Non- adjacent Total
11 1
22
32 4
93 8
12
23
28 2 30
36
100
Continuous Discontinuous Total
9 2
22 23
29 7 36
85
11
25 4 29
1
1
Percentages of all errors of commission.
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errors (see Table 3, bottom panel). If the relatively high interference caused by rotation in recalling good patterns is excluded, there is nothing special in the results compared with Experiments 1 and 2. The results do not provide evidence for the importance of verbal labelling. The loss of information is roughly equivalent in “good” and random stimuli. Therefore, the benefit subjects possibly have from using verbal labelling does not help them against the interference caused by mental rotation. It means that the “good” form superiority is caused by pictorial or conceptual rather than verbal factors.
EXPERIMENT 4 An important property of “good” forms is that they can be easily distinguished from their background, if the background has a random form. If the effect of the good “Gestalts” is really perceptual, one should be able to benefit from the good forms compared to random forms, even though both had been embedded in the same stimulus. In this experiment the recall of “pure” “good” and random patterns are compared with the retention of “good” and random patterns embedded in the same stimulus. The embedding of “good” forms or their fragments and the randomization of the background should also cause “perceptual” competition and therefore impair the recall of the “good” forms. In this way the experiments should provide a new type of evidence for the sharing of processing resources between images and percepts.
Method Subjects. Twelve first-year psychology students participated to the experiment. They were given a course credit for their participation. Stimuli. Eighteen dot matrixes were read onto a tape. None of the good or totally randomized patterns had been used in the previous experiments. In six of the dot matrixes there were 14-15 dots forming a “good” pattern (Good Forms); in another six the dots formed a random pattern (Rand. Forms); in the remaining six half of the dots belonged to a “good” form (Good Parts) and the other half was randomized (Rand. Parts). These stimuli were made by randomizing half of the points in some of the patterns used in the previous three experiments. Procedure. The procedure was the same as in the previous experiments.
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Results and Discussion The experiment replicated the previous good vs. random pattern effects. The overall differences between conditions were significant, F(3, 33) = 51.38,p < 0.001.Comparison of individual means with Duncan’s multiple range test showed that “good” patterns were recalled substantially better than random patterns (CR = 13.64,p < 0.001). The difference between “good” and random parts was also significant (CR = 7.22, p < 0.05) as well as the differences between random stimuli and random parts and good stimuli and “good” parts (CR = 7.22, p < 0.05). The error distribution was very similar to the previous experiments. Adjacent and continuous errors of commission are clearly more frequent than non-adjacent or discontinuous errors in the total of 509 errors. In Table 4, “good” part vs. random part comparisons have not been made, as it is not possible to ascertain, say with an error of commission, to which part of a stimulus it belongs. Again, the majority of errors are adjacent errors-i.e. subjects put a piece into a wrong cell next to a correct location. Though the number of non-adjacent cells is smaller than the number of adjacent cells, the distribu-
FIG. 5. Embedded good patterns. The results of the fourth experiment (percentages of correctly recalled dot locations).
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TABLE 4 Adjacent and Non-adjacent Location Errors (Top) and Continuous and Discontinuous Location Errors (Bottom Panel)
G
HR
R
Total
Adjacent Non-adjacent Total
10
38 1 39
47
95 3 100
Continuous Discontinuous Total
11
1 I1 0 11
30 9 39
2
48 37 13 50
79 21 100
Percentages of all errors of commission.
tion is far too biased to be caused purely by random guessing. Obviously, subjects have some idea about the correct location, but they fail to encode it precisely. The same phenomenon has also been found in experiments on chess players (Chase & Simon, 1973). The degree of randomness increases the number of probability or adjacency errors. This suggests that good Gestalt helps subjects in locating the dots precisely. This is naturally associated with the ease of recall. A high percentage of correct recalls decreases the probability of errors. Contiguity errors are more common than discontinuous errors. Subjects are more apt to “guess” a location that is next to an already existing group of pieces than a location that is separate. If the two types of errors are viewed as a whole, it seems that subjects do not make blind guesses. They like to group pieces into larger continuous chunks, or if they recall single pieces, they do it because they have a rough idea about the correct location. The results show that subjects are fully able to extract good forms from auditorily presented stimuli and benefit from them, even though they were embedded among random dots, but the performance was never as successful as in the recall of “pure” good patterns. Subjects were also better able to recall the random dots in half-randomized matrixes compared to the totally randomized matrixes. This suggests that the subjects relied on “good” forms to support the encoding of random forms. They constructed illusory “good” patterns by associating random dots with the fragments of “good” patterns. The selection of a “good” pattern is thus not an absolutely determined process. When there is a random background, subjects are able to construct alternative chunks. They may in this way lose some dots in good fragments, but this can be compensated by the corresponding rise in the recall of randomized dots.
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GENERAL DISCUSSION In all four experiments “good” patterns were more successfully recalled than scattered ones. The order of presentation, the speed of presentation, and the rotation of stimuli impair the level of performance. The impairment is in the first case larger with “good” forms than with random but roughly equal in the latter case. The last experiment also showed that subjects are able to use fragments of “good” forms and to some extent associate random background dots with them, which means that they are to some degree able to select among the alternative interpretations. No naming effect could be shown, but the adjacency and continuity properties of the errors of commission proved to be strong. The data support the main hypothesis. Subjects benefit from the “good” visual organization of stimulus patterns, despite the fact that the patterns are presented auditorily. The processing resources used in the Gestalt organization of visual percepts are also used in processing visual images, and therefore the resources used in perceptual organization are shared to some degree with the resources used in constructing visuo-spatial representations from auditory inputs. The speed of presentation effect is logical. It is well known that images have a construction time, and therefore the increase in the speed of presentation decreases the number of recalled pieces (Kosslyn, 1980). The order of presentation effect can be explained in terms of visual information chunking. The randomized order of presentation impairs recall, as it impairs the use of some Gestalt principles such as proximity. In randomized presentation subjects must keep floating dots or dot groups much longer in the working memory before they are able to find the closest associates and build suitable chunks. The nameability of forms does not seem to have any important role. Perhaps this is due to the fact that subjects must first be able to form the image before they are able to name it. As only one object is used per stimulus, the familiarity of the names cannot greatly aid the storage and retention of the stimuli. Experiment 4 showed that subjects may construct alternative representations. They are able to associate random dots with fragments of “good” forms. This suggests that they may use some perceptual-like selection in encoding random positions. The stimuli in the experiments were auditory. They did not contain any visual Gestalt properties; however, visually “good” forms were recalled much better than random ones. Undoubtedly, subjects have first translated the verbal stimuli into propositional format in order to understand them. The major problem is, however, how the Gestalt properties are obtained. The theoreticians are surprisingly unanimous on the Gestalt-related questions. The grouping processes responsible for Gestalt properties are
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usually assumed to take place at a very early stage. Marr (1982) suggested that Gestalt properties are encoded in the construction of primal sketch (Marr, 1982). Accordingly, Pylyshyn (1978) argues that Gestalt properties are encoded by a “transputer”, which is responsible for transforming physical energy into symbol structures. This “transputer” he assumed to be excluded from the process of imaging, though the results of transputing can be stored in long-term memory. Kosslyn (1991) argues that Gestalt properties are encoded at early processing state in visual buffer. Kosslyn (1991), differently from Pylyshyn (1978), assumes that perceptual learning can take place in the early stage of processing. Kosslyn (1991) assumes also a pattern activation subsystem, in which visual patterns are stored. These patterns correspond to shapes of objects or parts of objects. The perceptual Gestalt grouping is assumed to have its origin in an early phase of visual processing. With respect to the current results, this would mean that auditory stimuli should have access to the processing resources responsible for early visual stimulus processing. However, the access to earliest perceptual stimulus coding can hardly be the right explanation. It would be in contradiction with the bottom-up processing assumption. A problem with this explanation is also the sufficiency of Gestalt properties. This means that the Gestalt properties can provide the form of a representation but not their content. In the case of percept the issue is simple, because physical stimulus information provides the objects, but when the presentation is auditory, the origin of objects is unclear. Consequently, I prefer to search for some other origin of the “good” form superiority rather than visual buffer processing. Pattern memory provides an alternative explanation to the visual buffer. The verbal stimuli could activate a number of patterns, and these activated patterns might be used in the construction of the final representation. This kind of procedure would be very similar to what happens in chess players’ recall of auditorily presented chess positions and games (Saariluoma, 1989, 1991b). Chess players transform verbal knowledge into visuo-spatial images using their pre-learned chess-specific patterns. The pattern construction view can be supported by the results. Subjects made a substantial number of errors. They forgot totally or dislocated slightly parts of the stimulus patterns, which suggests that they constructed the final representation of elementary parts and did not encode it as a single whole. If they had a clear idea of the total “Gestalt” of a stimulus, they would dislocate not only some of the parts, but the whole. The randomization of reading order impaired subjects’ performance, but it did not totally destroy the representation. It made subjects lose some of the patterns, but not all. This phenomenon also supports part-by-part encoding. In Experiment 4 the subjects actively used random dots and
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associated them into “good” parts. However, it is far from clear whether the random dots could be in harmony with the parts of one single “Gestalt” or only with the parts with which they were associated. The above arguments suggest that the origin of representation is in some pattern activation subsystem or some other visual pattern storage rather than in the early visual processing systems. According to this alternative “good” form superiority is based on the “good” form of the stored patterns and not on the early physical stimulus encoding. Also, it is logical to assume that propositional information can be better used to obtain information from the pattern activation subsystem than from visual buffer (Kosslyn, 1991). Finally, one may ask whether visual images share Gestalt properties with percepts. The answer seems to be yes in so far as pattern storage is concerned, because pattern-activation-storage-type memories are run topdown and bottom-up. It is not possible that our percepts would not be automatically enriched by the pattern information. On the other hand, pattern storage is also used to construct images with or without the immediate presence of the object. In fact, we very probably use this storage to build up images of objects that do not exist, such as centaurs. Therefore, the “output” of the pattern storage is not always a percept. Subsequently, a tentative answer to the main question could be that images and percepts share Gestalt properties, but only through the pre-learned pattern information.
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Farah, M. (1988). Is visual imagery really visual? Overlooked evidence from neuropsychology. Psychological Review, 3, 307-317. Farah, M.J.. & Smith, A.F. (1983). Perceptual interference and facilitation with auditory imagery. Perception & Psychophysics, 33, 475-478. Finke, R.A. (1980). Levels of equivalence in imagery and perception. Psychological Review, 87, 113-132. Finke, R. (1985). Theories relating mental imagery to perception. Psychological Bulletin, 98, 236-259. Garner, W.R. (1974). The processing of information and structure. Hillsdale, NJ: Lawrence Erlbaum Associates, Inc. Harber, R.N. (1979). Twenty years of haunting eidetic imagery: Where is the ghost? The Behavioural and Brain Sciences, 2, 583-629. Kosslyn, S. (1980). Image and mind. Cambridge, MA: Harvard University Press. Kosslyn, S.M. (1987). Seeing and imagining in the cerebral hemispheres: A computing approach. Psychological Review, 94. 148-175. Kosslyn, S.M. (1991). A cognitive neuroscience of visual cognition: Further developments. In R.H. Logie & M. Denis (Eds.), Mental images in human cognition. Amsterdam: North Holland. Kohler, W. (1935). Gestalt psychology. New York: Harbinger. Lasaga, M.L. (1989). Gestalts and their components: Nature of information-precedence. In B.E. Shepp & S. Ballesteros (Eds.). Object perception: Structure and process (pp. 165202). Hillsdale, NJ: Lawrence Erlbaum Associates, Inc. Logie, R.H. (1986). Visuo-spatial processing in working memory. The Quarterly Journal of Experimental Psychology, 38A. 229-247. Marr, D. (1982). Vision. San Francisco, CA: Freeman. Paivio, A. (1971). Imagery and verbal processes. New York: Holt. Paivio, A. (1978). Comparison of mental clocks. Journal of Experimental Psychology: Human Perception and Performance, 4. Paivio, A. (1986). Mental representations: A dual coding approach. Oxford: Oxford University Press. Pylyshyn, Z.W. (1978). Imagery and artificial intelligence. In C.W. Sawage (Ed.). Perception and cognition: Issues in the foundations of psychology. Minnesota Studies in the Philosophy of Science, Vol. 9. Minneapolis, MN: University of Minneapolis Press. Richardson, A. (1969). Mental imagery. New York: Springer. Richardson, J. (1980). Mental imagery and human memory. London: McMillan. Saariluoma, P. (1989). Chess players' recall of auditorily presented chess positions. European Journal of Cognitive Psychology. I, 309-320. Saariluoma, P. (1991a). Visuo-spatial interference and apperception in chess. In R.H. Logie & M. Denis (Eds.), Mental images in human cognition. Amsterdam: North Holland. Saariluoma, P. (1991b). Aspects of skilled imagery in blindfold chess. Acta fsychologica, 77, 65-89. Saariluoma, P. (1992). Visuo-spatial and articulatory interference in chess players' information intake. Applied Cognitive Psychology, 6. 77-89. Segal, S., & Fusella, V. (1970). Influence of imaged pictures and sounds on detection of visual and auditory signals. Journal of Experimental Psychology, 83, 458-463. Shepatd, R., & Metzler, J. (1971). Mental rotation of three-dimensional objects. Science, 171, 701-703. Wertheimer. M. (1923). Laws of organization in perceptual forms. In W. Ellis (Ed.), A source book of Gestalt psychology. London: Routledge & Kegal Paul.
Revised manuscript received I 1 April 1992
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APPENDIX Non-nameable and Nameable Patterns from Experiments 1 and 2 and the Percentage of Subjects Who Have Classified a Particular Pattern Easy to Name
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0 0
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0 0 0 0 0
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30X
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0 0 0 0 0 0 0 0 0 0
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0 0
0 0
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20%
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