About the Memory Theme
Research
Memory Theme Members
Professor Harlene Hayne
Department of Psychology
hayne@psy.otago.ac.nz
http://psy.otago.ac.nz/staff/hayne.html
Memory development during infancy and early childhood
Over the past 20 years, an increasing number of researchers have argued that memory is not a unitary process, but rather is comprised of two or more neural systems that serve different functions and operate according to different principles. The notion of independent, multiple-memory systems has had a major impact on recent theories of memory development. According to the multiple-system view, memory development occurs in a discrete, stage-like manner with one memory system emerging significantly earlier than the other. Within this framework, an analogy is frequently drawn between the memory skills of young human infants and those skills that are spared in human adults with temporal-lobe amnesia. Amnesics, for example, perform normally on a variety of procedural memory tasks, but fail to perform normally on tasks that are thought to require declarative memory. Despite the prevalence the infant/amnesic analogy, the verbal nature or motor sophistication of most declarative memory tasks has precluded direct coparison between the memory performance of preverbal infants and the memory performance of adult amnesics.
Over the last decade, the study of deferred imitation has re-emerged as a valuable paradigm for examining memory in infants, children, and adults. In a standard deferred imitation paradigm, the experimenter demonstrates a series of actions with novel objects and the participant's ability to reproduce those actions is assessed following a delay. Because deferred imitation is based on a brief observation of the target actions, without prior motor practice, it has been argued that this paradigm provides a measure of declarative memory performance. The recent finding that human adults with temporal-lobe amnesia fail on traditional tests of deferred imitation provides the most conclusive evidence to date that deferred imitation yields a nonverbal index of declarative memory.
In our research programme we use deferred imitation techniques to document age-related changes in memory processing during the infancy period. The results of some of our most recent work have shown that infants as young as 6 months of age exhibit deferred imitation when tested for the first time after a 24-hour delay. This finding challenges the current view that infants are restricted to procedural memory processes prior to approximately 8-9 months of age. Our research has also shown that several important changes in declarative memory occur during the infancy period. First, retention increases as a function of age. When tested under similar conditions, 6-month-olds remember after delays as long as 1 day, 12-months-olds remember after delays as long as 1 week, 18-month-olds remember after delays as long as 1 month, and 24-month-olds remember after delays as long as 3 months. Second, the range of effective retrieval cues increases as a function of age. Although changes in the test stimuli or the test context disrupt retention by younger infants, these changes have no effect on retention by older infants.
The present findings have important implications for current theories of memory development. The finding that declarative memory emerges so early in development may force us to re-examine the explanatory value of the procedural/declarative distinction for age-related changes in memory processing. We propose that age-related changes in the specificity of effective retrieval cues, together with age-related changes in retention, contribute to a developmental increase in the accessibility of memory over the long term.
Selected Publications
Hayne, H., MacDonald, S., & Barr, R. (1997). Developmental changes in the specificity of memory over the second year of life. Infant Behavior and Development, 20, 233-245.
Barr, R., Dowden, A., & Hayne, H. (1996). Developmental changes in deferred imitation by 6- to 24-month-old infants. Infant Behavior and Development, 19, 159-170.
Hayne, H. (2004). Infant memory development: Implications for childhood amnesia. Developmental Review, 24, 33-73.
Simcock, G., & Hayne, H. (2002). Breaking the barrier: Children do not translate their preverbal memories into language. Psychological Science, 13, 225-231.