The discriminability of form among young children

JOURNAL

The

OF EXPERIMEhTAL

I’STCIIOLOGY

Discriminability

8,

418-431

of Form

(I%%)

Among

Young

Children1

ROSSLPN GAI~YES University

of California,

Berkeley

The ability of young children to discriminate accurately forms which varied in complexity, line type, and structure was investigated. Variations in complexity or number of sides, in form perimeter from linear to currilinear to combined linear-curvilinear, and in structure from symmetrical to asymmetrical (compact-dispersed) were increasingly difficult to discriminate as measured by both errors and latency of response. Sex and IQ wire unrelated to performance. It was found that, nursery, kindergarten. and first grade children were all above chance in performance, older children being superior. The relations of these data to developmental perceptual theory are discussed.

When children are asked to select stimuli which vary in physical dimensions, two types of information emerge: first, a measure of a child’s skill in discerning the variations; second, relations between stimuli characteristics and skill. Regarding the first set of data, a current view (Bruner, 1966) is that a child’s perception is ‘(stuck, autistic, diffuse, concrete, and unsteady.” In contrast, approximately 40 years ago, a child’s perception was viewed as discrimination ‘%o the limits of sensory acuity, seizing each thing in its uniqueness, noting every hair and flea of the particular dog” (Brown, 1958). Some current studies of infant (e.g., Bower, 1966)) child (e.g., Pollack, 1963) and animal (e.g., Ganz and Wilson, 1967) perception suggest that this earlier view of children’s “sensory acuity” may have some validity. Since these studies did not give information on form discrimination, the present study was undertaken. ‘This research was supported by USPHS National Institute of Mental Health grant MH11234 to the writer. The writer expresses gratitude for the continuing cooperation of Francis Boa.rders and Constance Ackerman of Beauvoir National Cathedral School and Peter Rice of Sidwell Friends School, Washington, D. C. Mrs. Epp Miller. Betty Bond, and Lynn Skclfo. George Washington University. were responsible for careful testing and tahnlation of the data, and William Mallory, University of California, Berkeley, assisted in the analysis of the data. Dr. Tom Trabasso, Princeton University, gave a useful critique of the manuscript. Dr. Norman Anderson, University of California, San Diego, has been helpful in suggesting methods of statistical analysis. Portions of this paper were presented at the American Psychological Association meeting, Washington, D. C., 1567. 418

DISCRIMINABILITY

OF

FORM

419

The metrics of children’s responses to form dimensions have not been delineated, although those for adults are quite extensive (Michels and Zusne, 1965; Brown and Owen, 1967). For adults, differences such as jaggedness, compactness, and elongation clearly alter speed of responding. The effect of these variables on responses of young children has not been intensively studied despite research (e.g., Suchman and Trabasso, 1966) showing stimulus variables do serve young children as cues in learning. Studies of children’s responding to form stimuli frequently use looking time as a dependent variable. In general, developmental differences in response to varying form structures are examined. For example, Munsinger and Kessen (1966) found that older children estimated asymmetric figures better than symmetric figures, but young children estimated symmetric and asymmetric figures equally well. However, Crudden (1941) found that young children had more difficulty differentiating asymmetrical embedded figures than symmetrical embedded figures. This dilemma was in part made more explicable by Forsman’s (1967) finding that younger 8s response time to symmetric and asymmetric figures varied with the task: on an estimation of sides task, no differences occurred, but on a matching task, response latencies to asymmetric figures were longer. Again, in the Munsinger et nl. (1964, 1966) studies, chilclrcn estimated and categorized IO-sided figures better than 5- and 20-sided figures. However, Thomas (1966) repeated the latter study with different results. Among 6- to 12-year-old children, attention to complexity increases as the number of sides increases, with 40-sided figures looked at longest. One explanation of the discrepant findings might reside in Attneave and Arnoult’s (1956) phrase, “Shape is a multidimensional variable.” More reliable indices of children’s responses to particular dimensions could be obtained if choice responses arc measured on several form dimensions simultaneously. The prcseat study measured children’s latencies and error rates in response to several dimensions of form. First, latency was chosen as a measure because adult discrimination latency (Brown and Andre-s, 1968) can be user1 as a distance measure in multidimensional scaling. Further, the subjective dimensions can be psychophysically predicted from form metrics. The present study investigates whether the finding that latency increases as complexity increases is also characteristic of children’s responses. On the basis of adult data (Brown and Andrews, 1968), young children should also take longer to differentiate figures which have more sides, are structurally complex, have a complex line type, and have a smaller magnitude of change. In addition, variation in contour produced by either subtracting from or adding to the total area of the base figure is examined (Fig. 2). The general thesis

is that children’s form pcrccption rcaemblcs that of adults in that similar physical stimulus characteristics :lll’ SWJl 2:: C’OlJll’lCS Zillti ht. :\a fOl’1JIR beromc more complex and thr change is still discritninable as an increase in complexity, latency incrcascxs. Second, this study varied cliscriminal~ilit~ of differences bet~ween forms, such as small size variations ( l-3 mm) , since looking time could be related to the child’s capacity to discriminate form variations, as well as to eit,her the child’s choice or the stimulus complexity. Children are often asked to find small form or size variations among forms but without any systematic attempt by the experimenter to scale the difficulty level of the stimulus variables used in the discrimination task. This leads to error source being attributed to sample or experimental conditions without consideration of t’hc effect of stimulus variables on performance. Finally, the oddity problem method was selected for this study, since it, permits measures of small form variations. The general thesis is that as sides, st,ructural complexity, and complexity of line type are still discriminable as increases in complexity, the error rate increases and reflects the complexity of the figure as accurately as latency measures. METHOD

Stimulus

Materials

The first set of stimulus materials consisted of 100 form-oddity problems. The level of difficulty was based on reports of young children’s perceptual skills (e.g., Hill, 1965; Osler and Kofsky, 1965)) and almost half of the problems were designed to be more difficult than young children could he expected to solve. Pilot testing was done on the youngest age group (4 years) and successive sets of increasingly difficult problems were pretested. The first 8s tested made few errors, and their high scores were attributed to either known perceptual skill or superior intelligence. After several 8s failed to make any appreciable number of errors, the problems were discarded and a new series of more difficult problems was designed. The second set of stimulus variables and their dimensions are listed below as shown on Figure 1. Within dimensions, the easier values are listed first: (a) two levels of Sidedness: 4 and 8 sides; (b) three levels of Structure: symmetrical compact (e.g., a square) ; asymmetrical-compact (e.g., a trapezoid) ; and asymmetrical dispersed (e.g., an arrow-type shape) (structure includes the variables of symmetry, compactness, and jaggedness) ; (c) three Line Types: linear, curvilinear, and combined linear-curvilinear; (d) three Size Changes were selected: 6-, 3-, and l-mm changes along the perimeter of figures approximately 1 square inch. The

DISCRIMINABILITY

OF

421

FORM

G-mm change was made by using two 3-mm changes on each odd figure. The area range for all figures in the series, as measured by a planometer, is 1.4.80 inches. The size changes varied shape several ways and varied structure two ways. The shape and structural variations comprised: ( 1) side length extended, (2) side length shortened, (3) corner cut off, (4) curvature increased, and (5) curvature decreased. A change in one side changes an adjacent side and the above categories describe the origin of the change, rather than the total physical change in shape. All figures were drawn by a professional draftsman to specifications. The variations in size were randomized among figures and addition to or subtraction from the area of the figure was counterbalanced within each of the dimensions (a-d abovej. The basic figures used are shown in Figure 1. An example of the oddity problem format is shown in Figure 2. In general, four same figures were compared with one figure in each of the three size changes, with an addition and a subtraction in each of the 3- and l-mm changes. Position of changes for the four corner figures were counterbalanced within basic figure groups. Prior to the final statistical analysis it was found that there was no significant difference in error rate between 6- and 3-mm figures; the probability of error was .09 for both problem sets (Suchman, 1967). Since there was no difference in error rate and since the 6-mm problems did not include the direction of change variable, these problems were not included in the final analysis. Thus, each stimulus item represents one level of sidedness, one structural level, one line type, one size change, either added or subtracted, in a 2 X 3 X 3 X 2 X 2 design or 72 test items. Four-sided

Base Forms

Eight-sided Line

Form Siructutes

FIG.

Ll”eOr

CUWlliW~i

1. Base

form

Combmatnn Linear-curwllnear

for each

Bose Forms

types

of the oddity

Ll”W,

problem

Curvtiinear

size changes.

Combination Ltnear-cuwlineal

422

FIG. 2. A form oddity example. In this esamplc, the odd item is in the lower right-hand corner. The form variables are four-sidpdncas. compact-asymmetrical structure, and linear line type. The size change is made by removing one millimeter from the length of the base line. Original display size is 5 X 5 inches.

Procedure The sample consisted of thirty Ss, ages 4.6-7.6 years, from a private school in Washington, D. C. There were 15 girls and 15 boys from nursery school, kindergarten, and first grade. The mean IQ was 135. The IQ range was 109-159. The majority of Ss were children of upper class parents as measured by income, occupation, and education. Children were individually pretested for visual acuity using a tumbling “E” chart and color blindness using the HRR test (Hardy, Rand, and Rittler, 1954). All 8s included in the study had 20-20 vision (corrected) and normal color vision. There were 10 oddity-training problems using different shapes (triangles and circles) than those used in the test items. Also, the discrimination was easier since t*he size changes were 8, 6, and 4 mm, rather than 3- and l-mm changes. All test items were presented in a dark gray console (Munsell value 4.5) with a 5 X 5-inch opening for the stimulus card. Behind the stimulus card was a field containing magnets locat.ed in the center of each of the five figures. The 8s’ task was to “point to the one not the same.” The Xs used a magnetic pointer which interacts with the magnetic field and prints (a) the latency from the time the shutter cover was drawn back to the time of magnetic contact; (b) a binary coding for correct-incorrect; and (c) the number of the stimulus item. To ensure constant lighting conditions and simulated northern light, the stimulus cards were lit with

DISCRIMINABILITY

OF

FORM

423

a MacBeth daylight lamp. The incident light at the screen was 90 footcandles, as measured with a Lesson light meter. Each s’s seating height was adjusted so that the center of the console display was at his eye level. Since the important variable was task performance, the Ss were given, systematically, four types of reinforcement. First, S preselected a toy from an array of several five-cent toys (e.g., magnets, gliders, necklaces, yo-yos). The X was told that’ he could have the toy when he finished playing the game. Second, S automatically received a marble for each correct response. Third, S was given corrective feedback on each incorrect response; that is, the part of the form which was different was pointed to by E. Fourth, S was verbally praised during t’raining and at the end of the session. The Ss had two sessions 1 week apart on the 72 form oddities. In the first session, the S had 6 training items and 24 oddity problems randomly arranged except for the exclusion of l-mm size changes. In the second session, the S had 4 training items and 48 problems randomly arranged except for the exclusion of 6-mm size changes. RESULTS

Two analyses were made of the data. First, the association between error and response latency scores and the form variables were investigated. Second, the effects of sex, IQ, and grade level on errors were analyzed. First, the error rate was assessedby a 2 X 3 X 3 X 3 X 2 analysis of covariance using repeated measures.In one analysis, the response latency scores were the covariate and adjusted the errors for the linear influence of response latency scores. In a second analysis, using the same method, the error terms were the covariate. In both analyses, the large majority of the correlates between the criterion and covariate were not significant at the .05 level. Most important, no significant correlations occurred in the treatment by 8s interactions. The frequency of significant correlations (4 of 62) between error and response latency scores were no more than could be expected by chance alone. Further, if the individual correlations are assessedin relation to degrees of freedom and number of treatment effects (main effects and all interactions), the few significant correlations no longer reach statistically significant levels (Guilford, 1956, p. 538). Therefore, two separate analyses of variance using repeated measures were done on the error rates and the responselatency scores. A 2 X 3 X 3 X 3 X 2 analysis of variance using repeated measureswas performed on the error data. The 6-mm size changes were not included in this analysis because first, 3-mm size changes yielded as few errors as 6mm problems (I = .14), and second, the 6-mm problems did not permit

424

ROSHLYK GAIKES

coiupai~isou of tlirectioii of change (each (j-mm change con&et1 of one 3-mm changc~adding to, and on<’3-mm change subtracting from, the total area). The analysis was made using the I’CLA Iz!i-bled I)rograrn 03V (Bennett and Franklin, 19541 ard then discarding the pooled error term. An error t*erm for each main effect was derived by the interaction of the effect with subjects, producing F ratio2 atljustetl for repeated measures. The analysis of variance on errors yielded significant F ratios for all main effects except direction of size changes. Table 1 shows the mean error rates and mean latcncirs for main effects of the analysis. Individual analyses of the tri-levels within the main effects were performed by t t’ests for correlated means. As seen on Table 1, the four-sided discriminations were easier than the eight-sided discriminations. Again , symxnetrical-coiiipact figures had lower error rates than asyrnnletrical-corIll,act figures (t = 3.67, p < .Ol 1 and the asymmetrical-dispersed figures producetl the highest error rate when compared with symmetrical-compact and asymmetrical-compact figures (t = 3.28, p < .Ol; t = 5.76, p < .OOl, respectively). Line type was not effective alone but the analysis clearly shows that linenrcurvilinear combined figures were easier to discriminate than linear or curvilinear figures (t = 2.43, p < .05; t = 5.35, p < .OOl, respectively). There was no significant difference in error rate between linear and curviTABLE

1

ME,~N ‘ERROR IRATE ‘4~1) MEAN LATENCY SCORES OF 30 Ss ox FORM DIMENSIONS OF OWITY PROBLEMS Dimensions Struct,ure Symmetrical compact Asymmetrical compact Asymmetrical dispersed Line type Linear Curvilinear Combined Linear-Curvilinear Sides Four sides Eight sides Size of oddity change Three mm One mm Direction of change Area added Area subtracted

x0. of problems

hlean

error

Mean latency (seconds)

24 24 24

2.59 4.30 5.42

8.32 9.66

13.9'2

24 24 24

4.27 Pi.06 3.00

11.02 13.62 7.2.5

36 36

4.86 7.45

8.30 12.96

36 36

3 .x3 8.78

6.59 14.67

36 36

6.50 5.83

11.05 10.21

DISCRIMINABILITY

OF

425

FORM

linear figures. The 3-mm size change had a lower error rate than l-mm size changes. There was no significant difference in direction of change. It is possible that larger size variations than I and 3 mm would produce a more observable effect on direction of change. The significant F ratios are shown in Table 2. In interactions as complex as the present analyses, some trends can be indicated. These trends cannot be taken to “explain” results without further research. Only one variable, line type, was significant in interaction with all other main

ANALYSIS

TABLE 2 OF VARIANCE OF FORM

A (8idedness) Subjects B (St,ruct,ure) Subjects C (Line Type) Subjects D (Size Change) Subjects E (Direction of Change) Subjects AXC Subjects BXC Subject,s CxD Subjects CXE Subjects AxCxE Subjects BxCxE Subjeck BxDXE Subjects CxDxE Subjects AxBxCxE Subjects AxBxDXE: Subjects BxCXDXE Subjects a The reported.

F ratios

for

1 29 2 ,58 2 58 1 2.4 1 29 2 58 4 116 2 5s 2 F8 2 58 4 116 2 58 2 58 4 116 2 58 4 116 the main

effeck

ODDITY

ERRORS

2.82 .17 2.54 .12 1.36 .14 11.56 .12 .19 18 1:37 12 :48 .ll 1 OQ .ll .81 .13 1.27 .15 2.52 10 .59 .08 .50 .09 .” 8 .08 .34 11 :73 10 and

for

all interactions

16.59 21.17 9.71 96.33

11.42 4.36 9.27 6.23 8.47 25.20 7.38 5.55 3.50 3.09 6.64

significant

at

<.Ol

are

cffccts. So other hignifi(~ant 2-1~~ interactions occur. Examining the twor rat? nwans corrc~rponding t.0 each of the main effect,s in the thrcca line types, it appears that when the line type was linear-curvilinear combined, the error rate was lower within sidedness, within structure, within size of change, and within additive or subtractive changes. The significant three-way and four-way interactions were less clear: sidcdness was statistically significant in only one three-way interaction, while lint type and additive vs. subtractive were significant in three threeway interactions. All variables wcrc represented in the significant five-way interactions and require a more complex explanation than afforded by t’his data. 1~1general, examining error rate means corresponding to each of the five main effects 011 Table 2, it appears that the easiest (lowest error rate) combination of stimulus characteristics was four-sided, symmetricalcompact, linear-curvilinear combined line type discriminat.ions where a 3-mm size change was subtracted from the standard. The highest error rate was in response t’o eight-sided, asymmetrical-dispersed, curvilinear discriminations where a l-mm size change was added to the standard. The analysis of variance performed on the response lat,ency scores had the same structure as the analysis of variance performed on error rate: namely, a 2 x 3 x 3 x 3 X 2 analysis using repeated measures. Again, the analysis of variance yielded significant F ratios for all main effects except direction of size change. Table 3 shows the significant F ratios in the analysis of variance and Table 1 the mean latency scores for each of t’he variables within the main effects. Not only are the same effects : ignificant with respect t,o time to solution as are significant with respect to error rate, but the direction of the intra-variable differences are identical; that is, response time to four-sided figures was less than to eightsided figures, response time to symmetrical-compact was less than to asymmetrical-compact figures (t = 2.10, p < .05). Responses to asymmetrical-dispersed have a longer latency than to symmetrical or asymmetrical-compact figures (t = 8.19, p < .OOl; t = 5.24, p < .OOl, resp&tively) . In this analysis, responses to linear figures took less time than to curvilinear figures (t = 3.26, p < .Ol) , but responses to linear-curvilinear combined line type took less time than to linear and curvilinear line type figures (t = 5.86, p < .OOl ; t = 7.89, p < .OOl, respectively). There were lower response latencies to 3-mm size changes t’han to l-mm size changes. There were no significant differences in direction of change. The significant two-, three-, and four-way interactions require further investigation. One major support for continuing investigation is that identical response patterns are observed in error rate and latency measures. Latency analysis is consonant wit’h error analysis as follows: least time was required to respond to a four-sided, compact-symmetrical, linear-curvilinear combined line type figure where a 3-mm size change

DISCRIMINABILITT

OE’

TABLE

427

FORM

3

ANALYSIS OF VARIANCE OF FORM ODDITY KESPONSE LATENCY SCORES Sourcea A (Sidedness) Subjects B (Structure) Subjects C (Line Type) Subjects D (Size Change) Subjects E (Direction of Change) Subjects AXC Subjects AxD Subjects AXE Subjects BxC Subjects BXE Subjects CXD Subjects Cx E Subjects AXBXC Subjects AxCXE Subjects AxDXE Subjects BXCXE Subjects BXDXE Subjects CxDxE Subjects AXBXCXD Subjects AXBXCXE Subjects AXCXDXE Subjects B>:CxDxE Subjects u The F ratios for the main reported.

df 1 29 a 38 2 58 1 29 1 29 2 58 1 29 1 29 4 116 2 58 2 58 2 .i8 4 116 2 58 1 29 4 116 2 58 2 58 4 116 4 116 2 58 4 116 effects

and

for

MS

F ratios”

11,727.28 254.67 6,168.34 184.74 7,379.67 204.46 35,194.69 501.71 374.17 96.54 X,655.55 175.67 2,074.96 157.31 2,275.53 128.27 1,519.43 118.62 859.08 136.05 2,586.54 179.93 3,667.99 182.15 412.37 114.63 2,144.51 158.07 872.67 89.97 6,905.Ol 205.11 2,441.31 142.72 2,035.62 12'2.19 343.64 96.85 983.44 142.80 1,301.82 138.30 3,522.16 133.66

46.04

all interactions

33.39 36.09 70.14

20.81 13.19 17.74 12.81 6.31 14.38 20.14 3.60 13.57 9.70 33.66 17.11 16.67 3.55 6.89 9.41 26.35

significant

at

<.Ol

are

The rclationahip between graphs ICTY~l :11rtl C’l’1’01‘ I’iltC’ wau c011q,alI!d by t test. As tsl1ectcd, the higher the gratlc, thcs lo\r-c~~~thcs error rate. Thus, first grade children make fc~er errors than kindergarten children (t = 2.90, p < .Ol i and kindergarten children make fewer errors than nursery school children ( t = 3.86, p < .Ol J This finding is no way contradicts the analysis of variance showing that young children, ages 4.6-7.6 years, can make exceedingly s111all l1erceptual tliscrimi11ations. The form oddity error rate among all Ss indicates that the probability of a S making an err01 on level I (6-mn1 size cl1angc1 was .09, on level 2 (3-mm size change I was .09, and on level 3 ( I-mm size cl1angc) was .23; all above chance level. The form orltlity percentage of errors per grade level was 7% fo1 first graders, 13": for kinclcrgartcn, and 3O'j; for nursery schoolers. The percentage correct is well above chance level. In addition, the Pearson r l)etwceii Sq’ IQ and error rat,e was -.02, indicating no relation bctwecn error rate and IQ I 1099159 range). Last, comparison of the me:111error rates of boys and girls were not significant (t = 0.891.

In tl1is study, young chil1lrcn wer;~ found to be surprisingly skilled in cliscrirninRlit1g small form d&ails. Replication of tl1is study with a larger anal more representative sample is currently under way. The stimuli will include 3-, 2-, and l-mm, rather than 6-, 3-, and l-mm changes in the odd figure. Though the present results are novel, t,hey are in accord with implications of some research suggesting that, younger children differentiate between pcrccptual stimuli with considerable skill. For example, Gibson and Yonas (1966) studying visual search behavior, discovered that second-grade children were as fast as older children and adults in scanning one and two targets, despite predictions to the contrary. Pollack (1963) found that, arno~lg children &I2 years old, a tachistoscopic prescntation of a line bisecting a field was perceived at. lower thresholds of illumination by the younger children than by the older children. Last, Wescott. and Tolchin (1966) report. that in a study of ident.ification of incomplete pictures, ‘%omc nursery school subjects do bet,ter than some college subjects and almost 11alfof the first grade scores are in the range of the college scores.” The authors conclude that “the lack of discontinuity in skill is related to personality variables.” It is just as feasible to

DISCRIMINABILITT

OF

FORM

429

relate high scores in visual task performance to the ability to differentiate small variations within the form stimulus dimensions. Another source of relevant data is the study of children’s attention. To the writer’s knowledge, only one study (Ricciuti, 19’63) has dealt with children’s attention to geometric detail vs. geometric form. Ricciuti found that preferred cue utilization was stable across several tasks and that for children ages 3-7 years, approximately 20% of all judgments were based on stimulus detail rather than geometric form. It is certainly clear that for the stimulus materials used, form was a more compelling source’ of attention than detail. But there were “some children at every age level for whom the predominant cues are the stimulus details rather than over-all shape.” Moreover, young children (Beilin, personal communication) ) on a sameness identity task, continually found small detail differences which were irrelevant to the concept being studied but apparent to the child. Podell (1965) also refers to such attention to ‘LirrevclantO cues, making it necessary, on the basis of a pilot study, to redesign test stimuli. Children’s perceptual skills currently arc clescribed as interfering with their ability to respond veridically (Beilin, 1964)) syncretic IWernrr, 1957), and nonfunctional in cognitive processes (Piaget., 1962). It is also apparent that there are areas of perceptual development where young children have difficulty, for example: the perception of diagonals (Rude1 and Teuber, 1963), the discrimination between right and left orientations (Sekuler and Rosenblith, 19641, and the confusions between b and cl, p and q (Davidson, 1935). However, despite young children’s multiple errors and multiple difficulties in perceptual discrimination, there is also no question that they seem to have excellent, if not superior, skill in cliscerning small detail variations. Earlier writers (e.g., Stern, 1924; Welch, 1939) described this fine perceptual skill of young children, but generally dismissed this skill as nonrclcvant to, or interfering with, cognitive development. However, despite multiple theories, there are no data demonstrating that perceptual skill inhibits the development of cognitive skill, In any event, inadequate information regarding the function of this skill does not counterindicntc recognition of young children’s perceptual skill. REFERENCES ATTNEAVE, F., AND AHNOULT, M. D. The yuantitativc study of shape and pattern perception. Psychological R&etin, 1956, 6, 452-471. BEILIE, H. Perceptual-cognitive conflict in the development of an invariant area concept. Journal of Experimentnl Child Psychology, 1964, 1, 208-226. BENNBT. C. 8., AND FRANKLIN, N. 1,. Stntisticnl onal& in chemistry rind the rhrmicnl industry. New York: Wiley, 1954.

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HOSSLTN

tiAI&ES

BOWER. T. G. R. Visual percrl)iion of human infants. Institute of HII~~:II~ I,c:uxinr colloquium, Univnsity of Cnlifr)k:~. Bcrkrlcy, 1967. BROWN, D. R.. AND ANDREWS. M. H. Visual form discrimination-mnltidin~cnsion:ll anal,vsrs. Perception und Z’s~~ciiophysic.s, 1968, 3, 401-406. B~owvr;, D. R., AND 0~~s. 0. H. Thr> metrics of visual form: Methodologicaal dyspepsia. Psuchologicnl R&elk, 1967, 68, 243-259. BROWN. R. How shall a thing be called? l’sychobogical Review, 1958, 65, 14-21. BRUNER, J. On cognitive growth: I. In J. Bruner and R. Olver (Eds.), St&es i,~ cognitive grozoth. New York: Wiley, 1966. CRUDDEN, C. H. Form abstraction by children. Journal of Genetic Psychology, 1941. 58, 113-119. DAVIDSON, H. P. A study of the confusing letters, “b. d, p, q.” Journctl of Genetic Psychology, 1935, 47, 452465. FORSMAN. R. Age differences in the effects of stimulus complexity and symmetrical form on choice reaction and visual search performance. Journal of Ezperimentctl Child Psychology, 1967, 5, 40%429. GANZ, L., AND WILSON. P. D. Innate generalization of a form discrimination without contouring eye movements. JolLrrlal of Compnratizle and Physiological Psychology, 1967, 63, 258-269. GIBSON, E’. J., AND YONAS. A. A developmental study of visual search behavior. Perception and Psychophysics, 1966, 1, 169-171. GUILFORD, J. P. Fundamental statistics in psychology and education. New York: McGraw-Hill, 1956. H.~RDI., L. H.. RAND. C., AND RITTLIXR. M. C. H.R.R. pseudoisochromatic plates. Ameriran Journal of Optometry, 1954, 44, 509-516. HILL, S. D. The performance of young children on three discrimination-lrarning taslx. Child Deuelopment, 1965, 36, 425-436. MICHELS, K. M., AXD ZUSNE. L. Metrics of visual form. Psychological Bulletin, 1965, 63, 74-86. MUNSINGER, H., AND KESSEN, W. Structure. variability and development. JOWW~ of Experimental Child Psychology, 1966. 4, 2049. MUNSINGER, H., KESSEN, W., AND KESSEN, M. L. Age and uncertainty: Developmental variation in preference for variability. Journal of Experimental Child Psychology, 1964, 1, l-15. OSLER. S. F., AND KOFSKY, E. Stimulus uncertainty as a variable in the development of conceptual ability. Journal of Experimental Child Psychology, 1965, 2, 264279. PIAGET, J. The origin of intelligence in the child. New York: Harper, 1952. PoDeLL. J. E. Perception of mirror images and learning to discriminate them. Paper given at Midwestern Psychological Association, March 1965. POLWCK. R. H. Contour detectibility thresholds as a function of chronological agr. PcJrceptunl Motor Skills, 1963. 17, 411-417. RICCIUTI, H. N. Grometric form and detail as determinants of comparative similarity jlldgmcnts in young childrrn. In A basic research program on reading. U. S. Office of Education Coop. Res. Project #639, 1963. RUDF,L, R. G., .~ND TEUBER, H. L. Discrimination of direction of line in children. Journal of Comparative and Physiological Psychology, 1963, 56, 892898. HERULER. R. W., AND ROSENBLITH. J. F. Discrimination of direction of line and thtl effect of stimulus alignment. Psychonomic Science, 1964, 1, 143-144. STII:RN, IT;. Psychology of early childhood. New York: Holt. 1924.

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OF

FORhI

431

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SUCHMAN,

the