JOURNAL

OF EXPERIMENTAL

Dimensional

CHILD

PSYCHOLOGY

Dominance

and

DON University

21,

175-189

Stimulus

(1976)

Discriminability

FERNANDEZ

of Victoria

The relationship between the discriminability of scaling stimuli and assessed dimensional dominance was investigated in three studies. Sixty kindergarten children were assessed using a psychophysical scaling method to determine JND values for the size, brightness, and orientation dimensions. Thirty of the same subjects were then assessed for dimensional dominance using stimuli of two levels of known discriminability, based on the obtained JND values. In a third experiment, the remaining 30 subjects were assessed for dimensional dominance using stimuli that systematically emphasized the values of one dimension relative to the other two dimensions, again based on obtained JND values. The results indicated that (1) kindergarten children were able to perform consistently during psychophysical scaling, and there was little variability between children in their judgments of stimuli. (2) the overall level of discriminability affects dimensional dominance scaling behavior, with subjects more likely to exhibit dominance for one dimension when all the values of scaling stimuli are high in discriminability, and (3) some support for the hypothesis that dimensional dominance scaling behavior can be manipulated by manipulating the relative discriminability of scaling stimuli was found, though the trend was not clear. The relative discriminability of scaling stimuli appears to have some effects on dimensional dominance scaling behavior of young children. However, some preexperimental bias to attend to a particular dimension seems to remain even when the values of all dimensions present are of equal and known discriminability. Dimensional dominance is a function of an interaction between discriminability of scaling stimuli and the experiential bias or perceptual set of the subject.

A number of studies with children have attempted to demonstrate selective effects in learning tasks due to attention to particular stimulus dimensions (e.g., Mitler & Harris, 1969; Suchman & Trabasso, 1966). The usual paradigm involves assessing children to determine which dimension out of the set of dimensions present is dominant or preferred, i.e., to which dimension does each child attend.’ Following scaling, a discrimination task is presented with either the dominant or a nondominant dimension relevant to problem solution. One reliable finding has been that when dominant dimensions are relevant, problem solution is facilitated, whereas when nondominant dimensions are relevant, problem solution is delayed. These results, along with similar results from other This research was at the University of and Linda S. Siegel for Child and Family

conducted as partial fulfi!lment of the requirements for the PhD degree Victoria. The author thanks Drs. Richard B. May, Sandra S. Smiley, for their valuable suggestions. Author’s address: Integrated Services Development, 1951 Cook Street, Victoria, British Columbia, Canada. 175

CopyrIght 0 1976 by Academic Press. Inc. All lights of reproduction in any form reerved.

176

DON

FERNANDEZ

learning tasks like transfer shift problems (e.g., Campione, 1969; May & Fernandez, 1974; Trabasso, Stave, & Eichberg, 1%9), have been interpreted as supportive of two-stage models of discrimination learning. However, one persistent problem in this area involves stimulus discriminability. Stimulus discriminability refers to the degree of similarity between values of a dimension. For example, with the form dimension a circle and a triangle would be highly discriminable, whereas a circle and an ellipse would be lower in discriminability. Imai and Garner (1965) and Trabasso and Bower (1968) warn against attributing behavior that may be due to the use of particular stimulus values to a construct assumed to reside within subjects, i.e., dimensional dominance. When a child matches stimuli during scaling, it is not clear whether the response is based on some internal perceptual bias or on the simple fact that the values of one dimension are more discriminable and thus stand out or elicit attention. The influence of stimulus discriminability on matching behavior has been demonstrated by Huang (1945) and Smiley (1972). Using random forms Smiley (1972) found that when a red three-turn form is paired on a scaling task with a green six-turn form, children match on the basis of color. When the same red three-turn form is paired with a violet 25turn form, children match on the basis of form. Thus when the values of the color dimension are highly discriminable relative to the values of the form dimension, color dominance results. When the values of the form dimension are more discriminable, form dominance results. This is in keeping with a number of theories that conceptualize dimensional dominance as a function of discriminability of cues (Kendler, Basden, & Bruckner, 1970; Lovejoy, 1968; Shepp & Zeaman, 1966). It seems apparent, then, that relative discriminability of dimensional values used in scaling and discrimination tasks must be controlled before invoking the concept of perceptual selectivity. Following the lead of Gliner, Pick, Pick, and Hales (1969), the present study examines the possible use of psychophysical scaling to control stimulus discriminability. It is proposed that the just-noticeable difference (JND) for change in the values of dimensions may serve as a standard unit of measurement applicable to stimulus discriminability. The amount of physical change that will be noticed on the size dimension, for example, should have exactly the same meaning as the amount of change noticed on the brightness or orientation dimension. Galanter (1%2) has argued against the use of classical psychophysical scaling methods. He suggests the use of the signal detection paradigm. However, scaling with young children as subjects involves restrictions not necessarily present when scaling adults. For example, the task and instructions must be relatively simple and not too long or demanding.

DIMENSIONAL

DOMINANCE

AND

DISCRIMINABILITY

177

Although the use of a signal detection procedure would allow assessments of systematic response biases and therefore result in more powerful assessments of physical discriminability, the simpler JND scaling technique was employed in the present work. The purpose of the study was to employ psychophysical scaling to assess JNDs for change in the size, brightness, and orientation dimensions (Expt 1). These scaled JNDs were then used to construct dimensional dominance scaling stimuli that had values of equivalent discriminability (Expt 2) or systematically emphasized each dimension relative to the other two by using more discriminable values (Expt 3). The goal in Expt 2 was to assess the effects of two levels of discriminability on dominance when discriminability is constant across the values of all three dimensions. Thus scaling cards were constructed with values of all three dimensions 2 JNDs apart or 4 JNDs apart. The goal of Expt 3 was to manipulate dominance by manipulating discriminability. To attempt this the values of one dimension were 4 JNDs apart, whereas the values of the remaining dimensions were 2 JNDs apart. EXPERIMENT

1

Experiment I involved psychophysical scaling with the dimensions of size, brightness, and orientation. The scaling procedure was a modified method of limits in which a standard and a comparison stimulus were paired on cards. Only one dimension was varied on each of three sets of cards: one for size, one for brightness, and one for orientation scaling. The two dimensions not varied were present but constant. The purpose of psychophysical scaling was to obtain just-noticeable differences (JND) values for each dimension. A JND is defined by Woodworth and Schlosberg (1954, p. 193) as that amount of physical change that will be noticed 50% of the time. The JND represents the amount of physical increase or decrease in the values of a dimension that will be detected one-half of the times that they are presented. Thus, the JND is a psychological representation of physical change. Method

Subjects The subjects were 32 boys and 32 girls from two kindergarten classes in two public schools. The age range of the children was 62 to 73 months with a mean of 68.2 months. According to parental occupation, one of the schools was located in a predominantly high socioeconomic residential area, whereas the second school was in a relatively middle-class area of the city. The testing was conducted during the months of January and February.

178

DON

FERNANDEZ

Stimuli

All stimuli were circles cut out of photographic paper and glued to 8 x j-in. white cards. Each card had a standard stimulus on the left located 1% in. from the side and 1% in. from the bottom. A comparison stimulus was located on the right of the card, the same distances from the side and bottom. There were three sets of cards, one for scaling each of the three dimensions: size, brightness, and orientation. The values of the two dimensions not being scaled were held constant at the standard value for each dimension. The values of the size-scaling stimuli were a standard of 2.0~cm radius circle and comparisons of 1.95-, 1.90-, 1.85-, 1.80-, 1.75-, 1.70-, and 1.65-cm radii. There were eight scaling cards, the first pairing the standard with another circle of standard size. The following seven cards had the standard paired with each of the seven comparison values. Thus from Card 2 through 8 there was a .5-m reduction per card of the comparison value’s radius. The brightness series of stimuli were obtained by varying the exposure time of photographic paper to a controlled light source. The brightness series consisted of Kodak Ektamatic T photographic paper exposed under a Chromega D6 enlarger set at 24 in. The 80-mm lens was set at f8. The first exposure time was 3 set, and each subsequent exposure increased by .2 sec. Eight values were taken from this series: 3.0, which was the standard, and 3.2, 3.4, 3.6, 3.8,4.0, 4.2, and 4.4, which were the comparison values. The brightness values corresponded approximately to Munsell’s neutral series values as follows: 3.0 (N8.25), 3.2 (N8.00), 3.4 (N7.75), 3.6 (N7.50), 3.8 (N7.00), 4.0 (N6.50), 4.2 (N6.25), and 4.4 (N5.75). The eight scaling cards were constructed exactly as in the sizescaling condition. The orientation series was constructed using Letraset tape l/32 in. wide. A l-cm section of tape was placed on the edge of each circle, pointing inward toward the center. For the standard value the line was located at 90” from the horizontal (at “12 o’clock”). The comparison values had the line moving in 2” steps in a clockwise direction. Thus the seven comparison values were 92”, 94”, 96”, 98”, loo”, 102”, and 104”. Again, the scaling cards were constructed the same as in the size- and brightness-scaling conditions. Two prescaling cards were presented prior to scaling to familiarize the child with the stimuli and the task. On the first card both circles were the standard values for all three dimensions. The second card had a circle of standard values on the left and a comparison circle on the right with the values of 1.60 radius for size, 4.6 exposure for brightness, and 40” line for orientation.

DIMENSIONAL

DOMINANCE

AND

DISCRIMINABILITY

179

Procedure

Each child was tested individually in the health room at each school. The ambient room light was kept between 50 and 55 fc. All cards were presented one at a time on a large white paper made out of the same material as the cards. The experimenter held the cards down, and the subject was not allowed to pick them up or move them. The prescaling cards were presented first, followed immediately by the scaling cards. The instructions spoken to each child requested that he look carefully at the two things on each card and tell the experimenter if the one over here (the comparison) was exactly the same as the one over there (the standard). Care was taken during the prescaling trials to make sure that the child understood the task and was aware of the three dimensions present. Each child was assessed on each dimension, i.e., received each of the three sets of scaling cards. There were four blocks of trials within each scaling condition, two descending and two ascending trials. The scaling was continuous, however, with the child shifted from descending to ascending after three consecutive “different” judgments were given and shifted from ascending to descending after three consecutive “same” judgments were given. Order of presentation of the three scaling conditions and beginning with descending or ascending trials were counterbalanced across all subjects. The subjects were assigned randomly to orders, with the restriction that there be an approximately equal number of boys and girls in each condition and each order. Results

Of the 64 children tested, two from each school did not complete the scaling task. These children were not included in data analysis. That left 13 boys and 17 girls in one school and 17 boys and 13 girls in the second school. Each child’s JND for each dimension was determined by taking the average of the four blocks (two ascending and two descending). Within each block, the JND was found by subtracting the value of the stimulus judged different from the value of the standard. For example, in size scaling, if the third card in descending order was judged to have circles of different sizes on it, the JND for that block would be 2.00 - 1.90, or 1 mm. The following data analyses are based on the average JND value for each subject on each dimension. To check for sex differences, r-tests were carried out on each dimension within each school. A11 the t values except two were less than 1, and neither of the two that was greater than 1 approached significance [t(28) = 1.51, p < .lO; t(28) = 1.68, p < .lO]. The absence of any sex

180

DON FERNANDEZ TABLE MEANS,

STANDARD

DEVIATIONS,

1 AND

RANGES

OF JNDs

Values Size (mm) Mean SD Range

Brightness (tenths of I-set exposure)

.I4 .04 .05-.25

.50 .I3 .3-.8

Orientation (deg) 8.42 2.04 4.50-12.00

differences allows the data to be collapsed across sex for further analysis. The mean JN-Ds for scaling with each dimension at each school, along with standard deviations and ranges, are presented in Table 1. The data were submitted to a multivariate analysis of variance, with schools and ascending or descending trials first as factors and the average JND for each of the three dimensions as dependent variables. The results uniformly indicated no significant main effects or interactions due to sex, school, or ascending versus descending order present either in the multivariate test or the univariate tests. Discussion

The mean JND value for each dimension across all 60 subjects would seem to be representative of the average child from the sample tested. Only two of the 60 children tested were greater than two standard deviations away from the grand mean for any dimension (both in size scaling). It appears that the kindergarten children tested were able to understand the psychophysical scaling procedure and made reasonably consistent judgments about the stimuli. In general, then, the mean JND for each dimension can be taken as reasonably representative of an individual child’s sensitivity to changes in the values of that dimension and, therefore, can serve as an index of discriminability that applies to the particular population scaled and the particular dimensions and values used. EXPERIMENT

2

Experiment 2 involved dimensional dominance scaling with stimuli of predetermined discriminability. The JND values for size, brightness, and orientation arrived at in Expt 1 were used as units of measurement to construct the scaling stimuli for dominance scaling. It was reasoned that values that are 2 JNDs apart on each dimension should be available but not emphasized, whereas values 4 JNDs apart should be both available and emphasized. Two sets of dominance-scaling cards were prepared. The values of

DIMENSIONAL

DOMINANCE

AND

DISCRIMINABILITY

181

size, brightness, and orientation differed by 2 JNDs for one set and by 4 JNDs for the second set. The effects of scaling with these two sets of cards might be in one of two directions. Scaling with the emphasized (more discriminable) 4-JND cards might result in more unidimensional responding as compared to scaling with 2-JND cards. This could result if the child gets “locked in” to one dimension by the highly discriminable values of that dimension. Thus the first dimension that gets his attention might hold it throughout scaling. Conversely, scaling with 4-JND cards might result in more equal dominance assessments as compared to 2-JND cards. This could occur if the equally emphasized but usually nondominant dimensions, to which the child would not normally attend, now get some attention due to their more obvious presence. Method

Subjects The subjects were 30 of the 60 kindergarten children who successfully completed Expt 1. These children had experience with all three dimensions employed in dominance scaling by virtue of Expt 1 psychophysical scaling. There were 15 children from each of two schools. Three boys and four girls from one school and four boys and four girls from the second school were randomly assigned to the 2-JND scaling condition. The remaining eight boys and seven girls were assigned to the 4-JND scaling condition. Stimuli The scaling procedure employed was a variation of one outlined by Seitz (1971). All cards were 8 x 5-in. white cardboard with three figures glued on in triad fashion. There were 10 free-choice cards on which the three figures could be logically grouped into pairs matched as having the same value of size, brightness, or orientation. In addition, there were 18 forced-choice cards, six for each dimension. On the forced-choice cards only one dimension was the same value in two of the three figures, whereas the values of the remaining two dimensions were distinctly different in all three figures. Thus, a logical match could be made only on one dimension. This procedure does not provide a measure of psychological distances between dimensions; however, it does provide an assessment of the rank ordering of the dimensions in dominance. The total deck consisted of 28 cards. The first five cards were freechoice cards, and the remaining 23 cards were randomly arranged from the forced-choice cards and the other five free-choice cards, with the restrictions that there be one free-choice card in every four or five trials and that each type of forced-choice card be present in every four of five trials with no more than two in a row of the same type.

182

DON

FERNANDEZ

The values of the free-choice 2-JND scaling cards were as follows: size, 2.00- and 1.70-cm radius; brightness, 3.0- and 4.0-set exposure: orientation, 90 and 106” clockwise from the horizontal. The corresponding values for 4-JND scaling were 2.00- and 1.40-cm, 3.0- and 5.0-set, 90 and 122”. On forced-choice cards the matched values were the same as those on free-choice, and the three values used to represent a dimension as an illogical match were as follows: size, 1.20-, 2.00-, and 2.90-cm; brightness, 3.6-, 4.8-, and 6.0 set; orientation, 90, 130, and 170”. These values were used for both 2- and 4-JND forced-choice cards. The particular triad combinations of all scaling cards were selected randomly from the total possible combinations of each type of card. The same particular triad combination was used for each card in both the 2and 4-JND decks, and the same order of cards was maintained in both decks. Thus, the only difference between the two decks was in the values employed. Procedure

The subjects were tested individually in the same health room at each school used in Expt. 1. The ambient room light was kept between 50 and 55 fc. All subjects were tested between 2 and 3 weeks after their participation in Expt 1. Cards were presented directly in front of the subject on a cardboard blotter made of the same material used for the cards. An intertrial interval of 10 set was maintained throughout all scaling. The following instructions were spoken to each subject: “I have some cards here I’m going to show you one at a time. See these three things (pointing to the stimuli)? I want you to look very carefully at these three things and tell me which two of these three things you think are the same, which two are most alike. These two, these two, or these two (pointing to each pair in turn).” No reinforcement was given after responses. The only feedback provided was “Now let’s do these two.” If the child claimed that no two stimuli were alike on forced-choice trials, he was told to pick two that seemed most alike. If, during scaling, a subject consistently adopted a strategy on forcedchoice cards, the strategy was noted on the data sheet, and no credit was given for fortuitously correct responses. For example, a sizedominant child may consistently match the two smallest stimuli on each forced-choice card. Such a strategy would provide correct responses for one brightness and one orientation forced-choice card. Scoring

Rationale

The total number of matches on each dimension on free-choice cards and the number of correct matches on forced-choice cards were tabu-

DIMENSIONAL

DOMINANCE

AND

DISCRIMINABILITY

183

lated for each subject. There were six scores for each subject, one for each dimension on free-choice cards and one for each of the three types of forced-choices cards. A raw data matrix was constructed that had the six categories of scores as rows and subjects as columns. Following a suggestion made by Seitz (1971), the pattern of scores for each subject was examined to classify the subject’s dominance. It was reasoned that if a subject does have a dominant dimension, he should match all or most of the free-choice cards on the basis of similarity on that dimension. He also should be correct in his matches of the forcedchoice cards using that same dimension, while making illogical matches on forced-choice cards using the other dimensions. Thus, what Seitz calls a “classic preference” in the present case would be a response pattern of, say, 10 size matches and zero brightness and orientation matches on free-choice cards plus six correct forced-choice size matches and zero forced-choice brightness and orientation matches. The inclusion of the forced-choice cards allows for the assessment of equal dominance. That is, the subject can, if required, use another dimension; he can readily shift his attention and match stimuli on the basis of similarity along a second dimension. Using the aforementioned scheme, criteria for exhibiting dimensional dominance were set. At least eight of 10 free-choice cards had to be matched on one dimension, at least five of six forced-choice on that same dimension had to be correct, and no more than three of six on any other forced-choice cards could be correct. These criteria were arrived at using binomial probabilities (except for the 50% level chosen for the three-of-six criterion). The values chosen are at or beyond the .05 level of chance for the first two criteria. This threefold approach to classifying dimensional dominance seems rather demanding, and subjects meeting all three criteria could be said to exhibit dimensional dominance with some degree of confidence. The criteria set for equal dominance were at least five of six forcedchoice cards correct for two dimensions. Thus, equal dominance assessment was based on forced-choice performance, irrespective of freechoice matching. Resu Its

Applying the aforementioned criteria to the data results in 17 subjects exhibiting dominance for a single dimension, none exhibiting equal dominance for two dimensions, and 13 not satisfying the criteria for exhibiting dominance. The frequencies of dominance in the 2-JND scaling conditions were one dimension dominant (5), equal dominance for two dimensions (0), and no dominance (10). The frequencies in 4-JND scaling were one dimension dominant (12), equal dominance (O),

184

DON FERNANDEZ

and no dominance (3).’ It can be seen clearly that 4-JND scaling resulted in twice as many subjects exhibiting dimensional dominance as compared to 2-JND scaling. The fact that only about half the subjects exhibited dominance supports the contention that the method of incomplete triads scaling commonly employed in this area includes many subjects inappropriately in dominance categories (see Seitz, 1971). There were no differences due to sex or schools (exact probability tests [Myers, 19581, p > .lO). Using the exact probability text, the probability of obtaining the previous observed frequencies was p = .014. Examining the frequency distribution in the 2-JND condition, the obtained frequencies were significantly different from chance (x2(2) = 10.00, p < .Ol). The obtained frequencies in the 4-JND condition were also significantly different from chance (x2(2) = 10.60, p < .Ol). Thus, in the 2-JND condition more subjects fell into the no-dominance category as compared to the dominance or equal-dominance categories. Similarly, in the 4-JND condition more subjects exhibited dominance for one dimension as compared to the equal-dominance and no-dominance categories. Significantly more subjects exhibited dimensional dominance for one dimension in the 4-JND condition as compared to the 2-JND condition (binomial probability = .025). Significantly more subjects exhibited no dominance in the 2-JND condition as compared to the 4-JND condition (binomial probability = .Ol 1). The aforementioned results were supported by a parametric analysis using the number of responses on free-choice cards as the dependent variables. A repeated measures analysis of variance was performed using the number of matches on a single dimension on the first five freechoice cards and the number of matches on that same dimension on the remaining five free-choice cards as two levels of the repeated measures factor. Four- or two-JND scaling served as two levels of the between factor. There was a significant effect due to 2- or 4-JND scaling [F(1),(28) = 7.12, p < .Ol]. a significant effect due to the block of free choice trials [F(1),(28) = 4.07. p < ,051, and a significant interaction between the two [F( 1),(28) = 5.15, p < .03]. The 4-JND scaling resulted in essentially the same mean number of matches across the two trial blocks (x1 = 4.53; iZ = 4.60), whereas 2-JND scaling resulted-in a drop in mean number of matches across the two trial blocks (x1 = 4.33; x2 = 3.20). The distribution of dimensional dominance for particular dimensions 1 Using less demanding criteria of seven of 10 free-choice and five of six forced-choice on the same dimension and no more than four of six forced-choice for another dimension correct (which are all based on binomial probabilities) yields the following frequencies for 2 JND: one dimension dominant (6), equal dominance (4), no dominance (IO): and for 4 JND: one dimension dominant (12). equal dominance (2). no dominance (1).

DIMENSIONAL

DOMINANCE

AND

across both 2- and 4-JND scaling conditions and 3 orientation-dominant subjects.

DISCRIMINABILITY

was 10 brightness-,

185 4 size-,

Discussion

The results of the nonparametric and parametric tests support the hypothesis that subjects might get “locked in” on a single dimension when the dimensions present are highly discriminable. If the level of relative discriminability is uniformily low for the dimensions present, subjects tend to exhibit less dominance and also lean toward more readily shift matching from one dimension to another during mixed forcedchoice and free-choice scaling. These statements are supported by the facts that 4-JND scaling resulted in more dimensional dominance and that subjects in 2-JND scaling were more likely to shift matching during mixed free- and forced-choice scaling. That is, subjects in 4-JND scaling were more likely to single out one of the three dimensions and match stimuli primarily on the basis of similarity along that dimension. This was true for both the first five and remaining five free-choice cards. In 2-JND scaling, subjects tended to use all three dimensions as a basis for matching (no dominance) more often than matching on the basis of a single dimension. These subjects also tended to shift the basis of matching during the latter five free-choice cards more often than subjects in 4-JND scaling. The fact that the majority of subjects who did exhibit dimensional dominance were brightness dominant is in keeping with other studies (e.g., Wolff, 1966). The effects of the discriminability of stimuli used in dimensional dominance scaling were controlled in the present study, and some dimensional dominance still resulted. This suggests that there is some other factor besides relative discriminability operating to produce selective matching on one dimension. However, the overall level of discriminability did have a dramatic effect on the number of subjects exhibiting dimensional dominance. Perhaps when discriminability is high, subjects attend to the dimension that they are otherwise preset or biased to perceive. It is also possible that when discriminability is high, subjects readily attend to the dimension with which they have had the most experience. When discriminability is low, subjects may scan the array of stimuli, searching for some basis for matching, and thereby gain exposure to several or all of the dimensions present. Latency data would be useful in examining this question, since one might expect longer latencies with lower discriminability of stimuli if the previous argument is valid. It is of interest to note that even with the rather stringent criteria for dimensional dominance employed in the present study, over half of the subjects tested were assessed as having one dimension dominant. This is more than the number of subjects classified as having “strong preferences” by Seitz (1971), who assessed 51 of 144 kindergarten children as

186

DON

FERNANDEZ

having exhibited dimensional dominance. Perhaps the discrepancy in the two studies is due to the fact that the relative discriminability of all the dimensions was essentially constant in the present study, whereas the discriminability of the stimuli used in the Seitz study was not assessed. It is possible that the stimuli used by Seitz were relatively low in overall intensity, which, according to the present study, would result in fewer subjects exhibiting dimensional dominance. However, comparisons between the two studies are difficult since the present research included three dimensions, Seitz employed only two dimensions, and the dimensions were not the same (Seitz used hue and form). It is not clear from the present results to what degree the effects of discriminability found with one particular set of dimensions and values will generalize to other dimensions and values. EXPERIMENT

3

The purpose of Expt 3 was to investigate the influence of emphasizing one dimension, relative to the others present, upon scaled dimensional dominance. An attempt was made to manipulate experimentally the dominance scaling behavior of subjects by manipulating the relative discriminability of the values used in scaling. To accomplish this, the 2- and 4-JND values employed in Expt 2 were combined in such a way that the values of one dimension were 4 JNDs apart, whereas the values of the other two dimensions were 2 JNDs apart. Three sets of dimensional dominance scaling cards were constructed. One set emphasized the size dimension by having its values 4 JNDs apart, whereas the values of brightness and orientation were 2 JNDs apart. Similarly, another set of cards emphasized the brightness dimension, and a third set of cards emphasized orientation. If discriminability can influence or determine dimensional dominance, then the dimension emphasized (and therefore more discriminable relative to the other dimensions) should be the dominant dimension or at the very least have equal dominance with one or both of the other dimensions. That is, an emphasized dimension should stand out and elicit attention and be used as a basis for matching stimuli. If a subject has a pre-experimental dominance for one of the nonemphasized dimensions, he might be expected to demonstrate an equal dominance for that dimension and the emphasized one. Method Subjects

The subjects were the remaining 30 children of the 60 who completed Expt 1 but did not participate in Expt 2. There were 15 children from each of the two schools.

DIMENSIONAL

DOMINANCE

AND

DISCRIMINABILITY

187

Stimuli

The same dimensions and values used in Expt 2 scaling were employed. However, three sets of scaling cards were constructed: size emphasis, brightness emphasis, and orientation emphasis. For the sizeemphasis cards, the values of size were 4 JNDs apart (2.00- and 1.40-cm radius), whereas the values of brightness and orientation were 2 JNDs apart (3.0- and 4.0-set exposure; 90 and 106” from the horizontal). For brightness-emphasis cards, the values of brightness were 4 JNDs apart (3.0- and S.O-set exposure), whereas the values of size and orientation were 2 JNDs apart (2.00- and 1.70-cm radius; 90 and 106” from the horizontal). For orientation emphasis cards, the values of orientation were 4 JNDs apart (90 and 122” from the horizontal), whereas the values of size and brightness were 2 JNDs apart. The dimensional dominance scaling procedure was identical to that of Expt 2. The scaling decks had the same triadic combinations and were in the same order as in Expt 2. The only difference between the three types of scaling cards was the values of the dimensions. Procedure

The children in this experiment also were tested individually in the health rooms of both schools. There were 10 children in each of the three scaling conditions. The procedure and instructions were identical to those of Expt 2. Results

A raw data matrix of the six types of scores for each subject was constructed as in Expt 2. The same criteria employed in Expt 2 were used to assess the dimensional dominance of subjects in Expt 3. Of the 30 subjects scaled in the three emphasis conditions, 18 exhibited dimensional dominance for one dimension. The distribution of dominance across the three emphasis conditions was as follows: for size emphasis, 4 size dominant and no brightness or orientation dominant; for brightness emphasis, 8 brightness dominant and no size or orientation dominant; for orientation emphasis, no size dominant, 3 brightness dominant, and 3 orientation dominant. In addition, 6 more subjects exhibited equal dominance for two dimensions: 3 for size and brightness, 1 for size and orientation, and 2 for brightness and orientation. Examination of the aforementioned frequencies shows that except for the orientation emphasis condition, dominance is perfectly predicted by the scaling condition. However, only brightness emphasis produced reliably more dominance for an emphasized dimension (binomial probability = .031); only 4 of 10 subjects were size dominant in the sizeemphasis condition, and there were as many brightness-dominant as orientation-dominant subjects in the orientation-emphasis condition.

188

DON

FERNANDEZ

Six subjects were assessed as exhibiting no dominance for either one or two dimensions: there were 3 such subjects in size emphasis, 2 in brightness emphasis, and 1 in orientation emphasis. Discussi

on

The results of Expt 3 are not conclusive. Some support was found for the contention that dominance scaling behavior can be manipulated by manipulating the relative discriminability of scaling stimuli. This is evident in the performance of subjects in the brightness-emphasis and, to a lesser degree, in the size-emphasis conditions. Further support can be seen if one combines the three equal-dominance size-brightness subjects with the four size-dominant subjects in size-emphasis scaling to get seven of 10 exhibiting some dominance for the emphasized size dimension. However, lacking a clear relationship between emphasized and dominant dimensions in at least two of the three conditions, such an argument must be tentative. As in Expt 2, brightness was most often the dominant dimension. This is particularly true in equal dominance where brightness was one of the two equally dominant dimensions in five out of six cases. It appears that a dimension, such as brightness, that is likely to be higher in some dominance hierarchy is more readily influenced by the relative discriminability of its values. The correspondence of assessed dominance in Expts 2 and 3 is substantial. In Expt 2 there were 10 brightness-, four size-, and three orientation-dominant children, and in Expt 3 there were 11 brightness-, four size-, and three orientation-dominant children. This pattern of results would be predicted by the literature and suggests that approximately one-third of kindergarten children would be brightness dominant when confronted with these three dimensions. In the present research, discriminability was manipulated by using psychophysically derived JND values as units of measurement. One dimension was emphasized, i.e., made relatively more discriminable, by multiplying the overall JND from Expt 1 by the constant 4 while multiplying the JNDs for the other two dimensions by the constant 2. Using the overall JND ensures that, on the average, the stimuli were either present or emphasized. A more powerful technique might be to construct a set of scaling stimuli for each subject, or groups of subjects, having the same thresholds, based on specific JND values. This would eliminate the possible situation of including a subject with very low threshold values in the same scaling treatment with a subject with very high threshold values. Alternatively, a signal detection paradigm could be attempted to eliminate systematic response error. Nonetheless, the use of psychophysical scaling appears to offer an operational approach

DIMENSJONAL

DOMINANCE

AND

DISCRIMINABILITY

to defining the dominance or salience of stimuli on physical stimulus properties.

189

that is based primarily

REFERENCES Campione, J. C. Intra- and extradimensional shifts in retardates as a function of dimensional preference. American Journal of Psychology, 1%9, 82, 212-220. GaIanter, E. Contemporary psychophysics. In New Directions in Psychology (No. 1). New York: Holt, Rinehart and Winston, 1962. Gliner, C. R., Pick, A. D., Pick, H. L., C Hales, J. J. A developmental investigation of visual and haptic preferences for shape and texture. Monographs for the Society for Research in Child Development, 1969, 34, Serial No. 130. Huang, I. Abstraction of form and color in children as a function of the stimulus objects. Journal of Genetic Psychology, 1945,66, 59-62. Imai, S., L Garner, W. R. Discriminability and preference for attributes in free and constrained classification. Journal of Experimental Psychology, 1%5, 69, 596-608. Kendler, T. S., Basden, B. H., & Bruckner, J. B. Dimensional dominance and continuity theory. Journal of Experimental Psychology, 1970, 41, 177-199. Lovejoy, E. Attention in discrimination learning: A point of view and a theory. San Francisco: Holden-Day, 1968. May, R. B., & Fernandez, D. Dimensional dominance and extradimensional shifts. Perceptual

and Motor

Skills,

1974, 38, 979-985.

Mitler, M. M., & Harris, L. Dimension preference and performance on a series of concept identification tasks in kindergarten, first-grade, and third-grade children. Journal of Experimental Child Psychology, 1%9, 7, 373-384. Myers, 3. L. Exact probability treatments of factorial designs. Psychological Bulletin, 1958, 55(l), 59-64. Seitz, V. R. Multidimensional scaling of dimensional preferences: A methodological study. Child Development, 1971, 42, 1701-1720. Shepp, B., & Zeaman, D. Discrimination learning of size and brightness by retardates. Journal of Comparative and Physiological Psychology, 1966, 62, 55-59. Smiley, S. S. Instability of dimensional preference following changes in relative cue similarity. Journal of Experimental Child Psychology, 1972, 13, 394-403. Suchman, R. G., & Trabasso, T. Color and form preference in young children’s concept attainment. Journal of Experimental Child Psychology, 1966, 3, 177-187. Trabasso, T., & Bower, G. H. Attention in learning: Theory and resea,rch, New York: Wiley, 1%8. Trabasso, T., Stave, M., 6t Eichberg, R. Attribute preference and discrimination shifts in young children. Journal of Experimental Child Psychology, 1969, 8, 195-209. Wolff, J. L. The role of dimensional preference in discrimination learning. Psychonomic Science, 1%6, 5, 455-456. Woodworth, R. S., & Schlosberg. H. Experimental Psychology (Rev. ed.), New York: Holt, 1954. RECEIVED:

November 4, 1974;

REVISED:

February 4, 1975