Developmental changes in infants' retention of visual stimuli.

In the first of 2 studies of visual recognition memory, 6- and 9-month-old infants were tested for their ability to differentiate novel from familiar test stimuli immediately following brief amounts of familiarization. After all problems were given, the paired test stimuli were re-presented for a test of delayed recognition memory. The delay test thus occurred after a period during which the infant had been looking at a number of different intervening stimuli. The 6- and 9-month-olds both showed significant recognition memory on 3 of the problems immediately following familiarization. While the older infants continued to show recognition on each of these problems after a delay, the younger infants failed to show evidence of retention on 2 of the 3 problems they had been able to recognize initially. In a second study, 6-month-olds were tested for delayed recognition under conditions where the interval between the familiarization and test was free of any interpolated visual stimuli. Despite this effort to minimize interference, the pattern of responding remained virtually identical to that of the first study. Thus the 6-month-olds appeared to have difficulty recognizing the stimuli over short delays, even in the absence of intervening distractors. The greater capacity for delayed recognition memory among the 9-month-olds is discussed in terms of other memory changes that may be taking place at that age.