Location memory in healthy preterm and full-term infants

Current research suggests that preterm birth, in and of itself, can have important consequences for the development of cognitive abilities. The research reported here investigated the development of egocentric location memory, and related attention behaviors, in preterm and full-term infants. In Experiment 1, healthy preterm and full-term infants were tested longitudinally at 2.5, 4.5, and 6.5 months of age on a location memory task. The preterm infants were tested at corrected age (i.e., age since expected due date). In this task, infants saw a toy lion hidden at one of two identical locations, a delay was imposed (5, 10, and 30 s at 2.5, 4.5, and 6.5 months, respectively), and then the lion either reappeared at the correct location (expected test event) or at the incorrect location (unexpected test event). At each age tested, the infants looked significantly longer at the unexpected than expected event, as if they remembered the correct location of hiding and found the reappearance of the lion at the incorrect location surprising. There were no reliable differences between the full-term and preterm infants. Results from a control experiment (Experiment 1A) suggest that the longer looking times to the unexpected event were not due to superficial differences between the two test events. Examination of attention behaviors (i.e., mean length of looks and trial length) during the encoding period also revealed no reliable differences between the preterm and full-term infants. However, looking times to the test events, and mean length of looks during the encoding period, decreased reliably with age. Experiment 2 was conducted to investigate whether the observed changes in attention could be attributed repeated exposure to the test events or to longer delay intervals. The results of Experiment 2 suggest that the observed changes in attention were not due to either of these factors. Together, the results of Experiments 1 and 2 suggest that (a) even very young infants can represent and remember the location of a hidden object, (b) attention behaviors during the location memory task change reliably with age, and (c) uncomplicated premature birth has no obvious effect on the development of location memory and related attentional abilities during the first 6.5 months corrected age.