Assessment of visual discrimination in infants : comparison of a conditioning method with traditional preference methods

The purpose of the present research was to develop a conditioning procedure with which to assess the visual discrimination, ability of infants, and to compare the results of this method with those obtained by traditional visual fixation preference methods. Infants twelve weeks of age were presented with black and white checkerboard stimuli varying on a physically graded dimension from 4x4- to 20x20 squares. Each stimulus was paired with a 2^x2^ checkerboard and measures of fixation time, span, and number of looks were recorded relative to each stimulus. Three groups of S_s were tested by the visual fixation preference procedures. In an effort to establish a procedure that was sensitive to the preferences of individual S_s, the stimulus presentation technique was varied among the groups. The results indicated, however, that the groups did not differ significantly with respect to the number of S_s evidencing discrimination. An operant conditioning procedure, designed to increase fixation time to one stimulus of a pair by presenting contingent visual stimulation as a reinforcer, was shown to be effective relative to a control procedure in which no reinforcement was administered. In comparison, with the visual fixation preference procedure, the experimental procedure was consistently superior in providing evidence of discrimination by individual 3_s. In comparisons with the criterion preference procedure, a modified preference procedure, the experimental procedure was usually iii superior for finding information about discrimination abilities of individual S_s. In addition, group results obtained for the preference studies indicated that infants twelve weeks of a,~'e most preferred a 10x10 checkerboard stimulus. These results were related to a theory of stimulus selection proposed by Dernber and Earl. Both zhe criterion preference procedure for groups of S_s, and the experimental procedure for individual S_s, indicated that the twelve-week-o-ld infants could discriminate the Ioxl6 from the checkerboard.