Infants’ Visual Recognition Memory for a Series of Categorically Related Items

Abstract

Six-month-old infants' (N = 168) memory for individual items in a categorized list (e.g., images of dogs or cats) was examined to investigate the interactions between visual recognition memory, working memory, and categorization. In Experiments 1 and 2, infants were familiarized with six different cats or dogs, presented one at a time on a series of 15-second familiarization trials. When the test occurred immediately after the sixth familiarization trial (Experiment 1), infants showed strong novelty preference for items presented on the fourth or fifth familiarization trial, but not for the items presented on the first three trials or on the sixth trial. When a brief (15-second) retention delay occurred between the end of the sixth trial and the test trials (Experiment 2), memory for the sixth item was enhanced, memory for the fourth item was impaired, and memory for the fifth was unchanged relative to when no retention delay was included. Experiment 3 confirmed that infants can form a memory for the first item presented. These results reveal how factors such as interference and time to consolidate influence infants’ visual recognition memory as they categorize a series of items.

ACKNOWLEDGMENTS

This research and preparation of this manuscript were made possible by National Institutes of Health grants HD49840 and HD56018 awarded to LMO. Some of these results were reported at the biennial meeting of the Society for Research in Child Development, March 2007, in Boston, MA, and at the biennial meeting of the Cognitive Development Society, October 2007, in Santa Fe, NM.

We thank Shaena McGivern, Lisa Christoffer, Emily Spring, and the undergraduate students in the Infant Cognition Laboratories at the University of Iowa and the University of California, Davis, for their help with this project.

Notes

¹It is always possible that we would have obtained different results if we had used different stimuli. However, we used the same stimuli and test pairs across conditions and across the three experiments, so we are confident that any differences across experiments we observe are due to differences in the variables of interest, and not due to differences in stimuli.

²This lack of an effect of pet experience on infants’ responding may seem surprising given recent results reported by Kovack-Lesh and colleagues (2008), but differences in the age of the infants, stimulus presentation format, and the number of different stimuli shown to each infant may contribute to the different findings with respect to pet ownership.

Note. On each line, the looking time to the item that would be presented during test is in bold.

³Although the linear trend was not significant in Experiment 1, but it was in Experiment 2, inspection of the means provided in Table 1 shows that responding over familiarization in the two experiments was very similar. Likely as a result of random fluctuation, infants in Experiment 1 had relatively low looking on Trial 2, making the overall trend look different from that in Experiment 2. But the patterns are more similar than they are different.