Early childhood is a period rich in experience in which young children are capable of acquiring, registering, and recalling events and episodes, as well as recognizing places and people. They can also vividly react to impressions, manifest pain and pleasure, and express love, jealousy and other passions. It is thus astonishing that this period is usually lost to memory entirely except for a few fragments. It was Freud who first described this lack of recall as a kind of amnesia and referred to it as infantile amnesia. Infantile amnesia is a universal phenomenon. No ne can remember his very early childhood, although the age at which a person forms what later will be his earliest memory, generally from three to four years, varies among individuals. Why are our earliest memories so rare, evasive, and random, and why can we not recollect them? For Freud, infantile amnesia was due to an internal force of repression. That is, having resolved the Oedipal crisis by rejecting our infantile sexual wishes, we cannot tolerate any associated memory that might bring them back to consciousness. Although very few other systematic attempts have been made to explain this phenomenon, psychological mechanisms (such as pro-and retroactive experience, stimulus generalization, changes in information processing) as well as neurological mechanisms (such as developmental changes in brain structure and function) have been advanced as explanatory factors of infantile amnesia (see for review Campbell & Coulter, 1976; Coulter, 1979; Spear, 1979). Renewed attempts to describe and explain infantile amnesia emerged from the recent discovery that memory involves different processes, one of which develops late during ontogeny. These new findings have led to the idea that infantile amnesia may be due to the absence of a functional memory system in early childhood (Bachevalier & Mishkin, 1984; Nadel & Zola-Morgan, 1984). The major aim of this chapter will be to
review findings indicating that retention of experience can proceed by two different systems, sub served by separate neural circuits, that develop at different rates during ontogeny. In this survey we will see that although young infants have the ability to acquire habits and skills, their capacity to form memories matures slowly during the first years of life. A final section will present evidence that, in primates, delayed maturation of the cortical association areas of the brain appears to be responsible for the delayed maturation of the memory system and, by implication, might be responsible for the phenomenon of infantile amnesia.