Infants' attentional preferences: Evidence of long-term recognition memory

358 INFANTS’ ATTENTIONAL PREFERENCES: EVIDENCE OF LONG-TERM RECOGNITION MEMORY Mary L. Courage, Mark L. Howe, and Leamre Fitzgerald Department of Psychology, Memorial University, St. John’s, NF, Canada, AlB 3X9 Novelty preference studies of infants’ recognition memory have shown that from birth (or before) infants can encode and store information and retrieve it over short retention intervals. Recently, the novelty preference paradigm has been employed to examine long-term recognition memory (Bahrick & Pickens, 1995). Specifically, using a between-subjects design these authors interpreted the changing pattern of infants’ attentional preferences for novel and familiar stimuli over a 3 month interval (i.e., from novel to null to familiar) as reflecting changes in the accessibility of the representation of the two stimuli in long-term memory. In a further exploration of these findings, we examined infants’ attentional preferences over time using within- and between-subjects manipulations. In Experiment 1 100, 3-month-old infants were familiarized with a pair of identical, dynamic visual stimulus arrays for 4, 40 second trials. Recognition of the array was tested in a pairedcomparison procedure after retention intervals of 1 minute, 1 day, 1 month, and 3 months (Multiple Tests group), or after only one of the intervals (Single Test groups). The proportion of total looking time (PTLT) to novel and familiar stimuli each on 2, 60 second retention tests was calculated. A potentially more sensitive dependent measure of recognition -- the length of the longest uninterrupted look (LL) to novel and familiar stimuli in the first 15 seconds of the retention test -- was also calculated (Diamond, 1995). In Experiment 2, 48 3-month-olds provided a replication of the first experiment over retention intervals of 1 minute, 1 day and 1 week. In Experiments 1 and 2 the PTLTs to the novel stimuli were evaluated with planned, single sample t-tests against a test value of 50%) and LLs to novel and familiar stimuli were compared with paired t-tests (Bonferroni corrected for the number of comparisons). The results of both measures showed a significant novelty preference at 1 minute and 1 day, and a null preference at 1 week for Multiple and Single Test groups. At 1 month, preference for the familiar stimulus was evident in the Multiple Tests group (PTLT and LL) and in the Single Test group (LL only). At 3 months, the groups diverged, and Multiple Tests infants showed a null preference and the Single Test groups showed a familiarity preference (both PTLT and LL measures). This pattern of preferences is generally consistent with the four-phase model of infant attention of Bahrick & Pickens (1995) in which visual preferences are related to retention time. Specifically, we found immediate or recent memory at 1 minute and 1 day (Phase l), intermediate memory at 1 week (Phase 2), and remote memory at 1 month (Phase 3). Preferences at 3 months differed in Single and Multiple Test groups with the former indicating continued remote memory, and the latter showing inaccessible memory (Phase 4). However, this interpretation of the 3 month Multiple Tests data remains tentative, as these infants’ repeated exposure to the familiar stimulus at the four retention tests might have served to forestall forgetting. If this was the case, the null preference shown by this group may reflect a second transitional phase in which the representations of novel and familiar stimuli coexist in memory and command equal attention, rather than inaccessibility of the trace. In sum, infants showed recognition memory over a 3 month interval by novelty preferences at 1 minute and 1 day and by familiarity preferences at 1 month (Multiple and Single Test) and 3 months (Single Test).