Perceptual and Motor Skills, 1991, 73, 115-123. O Perceptual and Motor Skills 1991
VIVIDNESS OF IMAGE A N D RETRIEVAL T I M E ' SHINSUKE HISHITANI Department of Literature Seinan Gakuin Universitj Summary.-The relationship between vividness of image and information-retrieval time was examined. In an integrated-image condition the retrieval time for a vivid-image set was shorter than the retrieval time for a dim-image set; on the other hand, there was no difference in retrieval time between vivid- and dim-image sets in a verbal-rehearsal condition. Since the retrieval time difference between the two sets in the integrated-image group was not an artifact of image-construction time or presentation position, it was concluded that vividness of image affected information-retrieval time in the integrated-image group. The results were explained in terms of a picture-metaphor hypothesis of imagery.
Those who propose that imagery can be explained in propositional terms (e.g., Anderson & Bower, 1973; Pylyshyn, 1973, 1981) assert that the experience of imagery is epiphenomenal. Pylyshyn, especialy, considers that, when imaging tasks such as mental rotation (Shepard & Metzler, 1971), image scanning (Kosslyn, Ball, & Reiser, 1978), and image comparison (Kosslyn, 1975) are presented to subjects, they use their tacit knowledge of physical laws in the real world and simulate what they believe would occur under the actual physical condtions corresponding to the tasks. According to his position, it is not necessary to postulate specific processes of imagery to explain the phenomena of imagery, and subjects' introspections concerning the function and nature of imagery are invalid. However, some findings suggest that this hypothesis about tacit knowledge must be reexamined. For example, children presumably d o not know the relationship between mental rotations and chronometric measurements in mental rotation tasks. Nevertheless, their reaction times increase as a linear function of the angular discrepancy between stimuli (Marmor, 1975, 1977). If the hypothesis about tacit knowledge is correct, subjects could predict the results of imagery experiments such as mental rotation and mental scanning after reading only the description of the tasks or after mentally simulating the processes of those tasks. Denis and Carfantan (1985, 1986), however, found that most subjects could not predict such results. Furthermore, the following findings are the strongest criticism against Pylyshyn's position: images can produce McCollough effects (Finke & Schmidt, 1977, 1978) and the 'I thank Dr. E. R. Valentine of Royal HoUoway and Bedford New CoUege and Professor D. F.
Mark, of Middlesex Polytechnic for their helpful advice in preparing this manuscript; and Dr. D. A. Johnson of Seinan Gakuin University for his helpful advice on English expression. I also thank the Editor and anonymous referees for their valuable comments on an earlier version of this manuscript. Please address correspondence to S. Hishitani, Ph.D., Department of Literature, Seinan Gakuin University, 6-2-92, Nishijin, Sawara-ku, Fukuoka 814, Japan.
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Mdler-Lyer illusion (Berbaum & Chung, 1981; Ohkuma, 1986), even if the subjects are not at all familiar with these phenomena. The above findings, especially image-induced McCollough effects, seem to suggest that imagery is a process with its own raison d'Ctre, in which perceptual information from memory is reencoded in a modality-specific way in a unique system referred to variously as imagery space (Hishitani, 1986), a visual buffer (Kosslyn, 1980), and consciousness (Marks, 1983). The newly reconstructed images are observed and treated as if they were visual stimuli. Therefore, the Miiller-Lyer illusion could be induced by mental imagery as well as McCollough effects. It is well known that the vividness of imagery fluctuates within and between subjects (e.g., Marks, 1983). According to the above considerations, much more information may be maintained in the imagery system in the case of vivid images than dim images. In other words, a vivid image may preserve more visual information than a dim one. This hypothesis is supported by the finding, through the analysis of sketches of images, that a vivid image has more visual features than a dim one (Hishitani, 1988). Furthermore, it is expected that, if an image is vivid, that is, there is a lot of information in the imagery system, i t will have a more powerful effect as a mental stimulus. Finke and Schmidt (1978) found that imagery induces a stronger McCollough effect in vivid imagers than in nonvivid imagers. This finding confirms the above expectation. Consequently, imagery is not epiphenomenal but a real mental entity, something "seen" as a mental picture, and vivid images function as perception-like stimuli. If so, vivid images can be "seen" more easily than dim ones. Therefore, it is predicted that subjects would retrieve information more quickly from vivid images than from dim images. I n the present study this last hypothesis was examined in an integrated-image condition which measured the time required to judge whether or not a target item is in a memory set of a concrete-noun triplet. A verbal rehearsal group was used as a control condition. METHOD
Subjects The subjects were 16 undergraduate students who volunteered to participate. Eight subjects (one man and seven women) were assigned to the integrated-image group; the remaining one man and seven women were assigned to the verbal-rehearsal group. Each subject in the verbal-rehearsal group was paired with one of the same sex in the integrated-image group. Subjects in the former group verbally rehearsed items for the period of time which the yoked subjects in the integrated-image group needed to construct an integrated image. Prior to the experiment, the subjects were asked which hand they used
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mainly for such daily manual skills as writing, eating with chopsticks, and using scissors. All the subjects were judged right-handed, because all of them reported that they used their right hands for the above activities.
Materials and Apparatus To construct four triplets for the memory sets, 12 concrete nouns were selected from a pool of 96 Japanese nouns which had previously been rated for imagery value on a seven-point scale (Hishitani, 1980). The mean imagery value for the 12 nouns was 6.6 (SD = 0.3). The remaining 84 nouns were used as negative probes; their mean imagery value was 6.5 (SD = 0.5). The four triplets were presented in eight different orders, one pair of subjects from the integrated-image and verbal-rehearsal groups being assigned to each of the eight orders. Each triplet was used successively in 42 trials where positive (elements of the triplet) and negative probes appeared with the restrictions that: three positive and three negative probes occurred in any six successive trials, neither positive nor negative probes occurred for more than three successive trials, and each negative probe was used only once in d 168 trials (four triplets x 42 trials). Each probe was written in katakana (the Japanese alphabet) with a black marker in the centre of a 21-cm x 20.4-cm white card. The visual angle subtended by each character was l o x l o and the visual angle between the left edge of the leftmost character and the right edge of the rightmost character was adjusted to 4O during tachistoscopic presentation. The warning signal was a 350-Hz square wave. The robes and white field, which were 80 cm from the subject, were presented using a three-channel tachistoscope (Takei Co.). A multipurpose latency measurement system (Hishitani & Yumino, 1976) was used to control the warning signal and to measure the retrieval time from probe onset to response onset (see Fig. 1).
Procedure The integrated-image group was instructed to relate the nouns to each other to construct an imaged scene. They were asked to judge as correctly and as quickly as possible whether a probe was in the image and to respond by pressing a green or a red switch which corresponded to a yes or no response. I n addition, the integrated-image group was required to refresh the image, make it vivid in every trial, and to report the disappearance of the image when it occurred. The verbal-rehearsal group was instructed to rehearse verbally the nouns for the period, as measured by stopwatch, which the paired subject in the integrated-image group needed to construct or refresh an image. They were also instructed to push the switches correctly and as quickly as possible to indicate whether the probe existed in the rehearsed triplet.
S. HISHITANI
VIVIDNESS OF IMAGE A N D RETRIEVAL T I M E ' SHINSUKE HISHITANI Department of Literature Seinan Gakuin Universitj Summary.-The relationship between vividness of image and information-retrieval time was examined. In an integrated-image condition the retrieval time for a vivid-image set was shorter than the retrieval time for a dim-image set; on the other hand, there was no difference in retrieval time between vivid- and dim-image sets in a verbal-rehearsal condition. Since the retrieval time difference between the two sets in the integrated-image group was not an artifact of image-construction time or presentation position, it was concluded that vividness of image affected information-retrieval time in the integrated-image group. The results were explained in terms of a picture-metaphor hypothesis of imagery.
Those who propose that imagery can be explained in propositional terms (e.g., Anderson & Bower, 1973; Pylyshyn, 1973, 1981) assert that the experience of imagery is epiphenomenal. Pylyshyn, especialy, considers that, when imaging tasks such as mental rotation (Shepard & Metzler, 1971), image scanning (Kosslyn, Ball, & Reiser, 1978), and image comparison (Kosslyn, 1975) are presented to subjects, they use their tacit knowledge of physical laws in the real world and simulate what they believe would occur under the actual physical condtions corresponding to the tasks. According to his position, it is not necessary to postulate specific processes of imagery to explain the phenomena of imagery, and subjects' introspections concerning the function and nature of imagery are invalid. However, some findings suggest that this hypothesis about tacit knowledge must be reexamined. For example, children presumably d o not know the relationship between mental rotations and chronometric measurements in mental rotation tasks. Nevertheless, their reaction times increase as a linear function of the angular discrepancy between stimuli (Marmor, 1975, 1977). If the hypothesis about tacit knowledge is correct, subjects could predict the results of imagery experiments such as mental rotation and mental scanning after reading only the description of the tasks or after mentally simulating the processes of those tasks. Denis and Carfantan (1985, 1986), however, found that most subjects could not predict such results. Furthermore, the following findings are the strongest criticism against Pylyshyn's position: images can produce McCollough effects (Finke & Schmidt, 1977, 1978) and the 'I thank Dr. E. R. Valentine of Royal HoUoway and Bedford New CoUege and Professor D. F.
Mark, of Middlesex Polytechnic for their helpful advice in preparing this manuscript; and Dr. D. A. Johnson of Seinan Gakuin University for his helpful advice on English expression. I also thank the Editor and anonymous referees for their valuable comments on an earlier version of this manuscript. Please address correspondence to S. Hishitani, Ph.D., Department of Literature, Seinan Gakuin University, 6-2-92, Nishijin, Sawara-ku, Fukuoka 814, Japan.
116
S. HISHITANI
Mdler-Lyer illusion (Berbaum & Chung, 1981; Ohkuma, 1986), even if the subjects are not at all familiar with these phenomena. The above findings, especially image-induced McCollough effects, seem to suggest that imagery is a process with its own raison d'Ctre, in which perceptual information from memory is reencoded in a modality-specific way in a unique system referred to variously as imagery space (Hishitani, 1986), a visual buffer (Kosslyn, 1980), and consciousness (Marks, 1983). The newly reconstructed images are observed and treated as if they were visual stimuli. Therefore, the Miiller-Lyer illusion could be induced by mental imagery as well as McCollough effects. It is well known that the vividness of imagery fluctuates within and between subjects (e.g., Marks, 1983). According to the above considerations, much more information may be maintained in the imagery system in the case of vivid images than dim images. In other words, a vivid image may preserve more visual information than a dim one. This hypothesis is supported by the finding, through the analysis of sketches of images, that a vivid image has more visual features than a dim one (Hishitani, 1988). Furthermore, it is expected that, if an image is vivid, that is, there is a lot of information in the imagery system, i t will have a more powerful effect as a mental stimulus. Finke and Schmidt (1978) found that imagery induces a stronger McCollough effect in vivid imagers than in nonvivid imagers. This finding confirms the above expectation. Consequently, imagery is not epiphenomenal but a real mental entity, something "seen" as a mental picture, and vivid images function as perception-like stimuli. If so, vivid images can be "seen" more easily than dim ones. Therefore, it is predicted that subjects would retrieve information more quickly from vivid images than from dim images. I n the present study this last hypothesis was examined in an integrated-image condition which measured the time required to judge whether or not a target item is in a memory set of a concrete-noun triplet. A verbal rehearsal group was used as a control condition. METHOD
Subjects The subjects were 16 undergraduate students who volunteered to participate. Eight subjects (one man and seven women) were assigned to the integrated-image group; the remaining one man and seven women were assigned to the verbal-rehearsal group. Each subject in the verbal-rehearsal group was paired with one of the same sex in the integrated-image group. Subjects in the former group verbally rehearsed items for the period of time which the yoked subjects in the integrated-image group needed to construct an integrated image. Prior to the experiment, the subjects were asked which hand they used
VIVIDNESS OF IMAGE AND RETRIEVAL TIME
117
mainly for such daily manual skills as writing, eating with chopsticks, and using scissors. All the subjects were judged right-handed, because all of them reported that they used their right hands for the above activities.
Materials and Apparatus To construct four triplets for the memory sets, 12 concrete nouns were selected from a pool of 96 Japanese nouns which had previously been rated for imagery value on a seven-point scale (Hishitani, 1980). The mean imagery value for the 12 nouns was 6.6 (SD = 0.3). The remaining 84 nouns were used as negative probes; their mean imagery value was 6.5 (SD = 0.5). The four triplets were presented in eight different orders, one pair of subjects from the integrated-image and verbal-rehearsal groups being assigned to each of the eight orders. Each triplet was used successively in 42 trials where positive (elements of the triplet) and negative probes appeared with the restrictions that: three positive and three negative probes occurred in any six successive trials, neither positive nor negative probes occurred for more than three successive trials, and each negative probe was used only once in d 168 trials (four triplets x 42 trials). Each probe was written in katakana (the Japanese alphabet) with a black marker in the centre of a 21-cm x 20.4-cm white card. The visual angle subtended by each character was l o x l o and the visual angle between the left edge of the leftmost character and the right edge of the rightmost character was adjusted to 4O during tachistoscopic presentation. The warning signal was a 350-Hz square wave. The robes and white field, which were 80 cm from the subject, were presented using a three-channel tachistoscope (Takei Co.). A multipurpose latency measurement system (Hishitani & Yumino, 1976) was used to control the warning signal and to measure the retrieval time from probe onset to response onset (see Fig. 1).
Procedure The integrated-image group was instructed to relate the nouns to each other to construct an imaged scene. They were asked to judge as correctly and as quickly as possible whether a probe was in the image and to respond by pressing a green or a red switch which corresponded to a yes or no response. I n addition, the integrated-image group was required to refresh the image, make it vivid in every trial, and to report the disappearance of the image when it occurred. The verbal-rehearsal group was instructed to rehearse verbally the nouns for the period, as measured by stopwatch, which the paired subject in the integrated-image group needed to construct or refresh an image. They were also instructed to push the switches correctly and as quickly as possible to indicate whether the probe existed in the rehearsed triplet.
S. HISHITANI
