What Infant Memory Tells Us about Infantile Amnesia: Long-Term Recall and Deferred Imitation

Abstract

Long-term recall memory was assessed using a nonverbal method requiring subjects to reenact a past event from memory (deferred imitation). A large sample of infants (N = 192), evenly divided between 14-and 16-months old, was tested across two experiments. A delay of 2 months was used in Experiment 1 and a delay of 4 months in Experiment 2. In both experiments two treatment groups were used, In one treatment group, motor practice (immediate imitation) was allowed before the delay was imposed; in the other group, subjects were prevented from motor practice before the delay. Age-matched control groups were used lo assess the spontaneous production of the target acts in the absence of exposure to the model in both experiments. The results demonstrated significant deferred imitation for both treatment groups at both delay intervals, and moreover showed that infants retained and imitated multiple acts. These findings suggest that infants have a nonverbal declarative memory system that supports the recall of past events across long-term delays. The implications of these findings for the multiple memory system debate in cognitive science and neuroscience and for theories of infantile amnesia are considered.Infantile amnesia refers to the difficulty adults have in accessing memories from the first years of life. One candidate explanation for this phenomenon is the immaturity of the memory system during infancy. The hypothesized immaturity has received support from two independent sources, developmental psychology and cognitive neuroscience. Regarding the former, Piagetian theory postulated that representation and recall were the product of development in infancy, not aspects of the initial state. He placed their onset at 18 to 24 months of age, during "stage 6" of the sensorimotor period. Piaget reported that a cluster of abilities synchronously emerged at this age-deferred imitation, symbolic play, high-level object permanence, and language. That all these blossomed synchronously demanded an explanation; Piaget's was that younger infants were confined to sensory-motor habits ("schemes") which could be retained, but there was no representation or recall of perceptually absent events until 18 to 24 months old. When representation became possible, it enabled the aforementioned cluster of behaviors to emerge.A second strand of related work derived from research in cognitive science and neuroscience. It was hypothesized that there are dissociable memory systems subserved by different neural structures (e.g., Sherry & Schacter, 1987;Squire, 1987). Neuropsychological studies on memory-impaired patients and experimental animals demonstrated that motor skills and habits could be learned and retained in the same individual who failed other memory tasks. A striking case derived from amnesic adults who could successfully execute motor routines they acquired over several trials, but could not remember having learned them. It was argued that there were (at least two) dissociable memory systems. One (spared in amnesia) was cal...

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