THE TIME WINDOW HYPOTHESIS - SPACING EFFECTS

A time window is defined as the interval between the occurrence of an initial event and the upper limit of the period within which new infor mation can be integrated with the memory representation of that event. The validity of the time window construct was documented in a prior r eport involving a categorization paradigm and in which a new exemplar was integrated into a previously established category. Presently, we a sked if there is a time window within which information can be integra ted across successive training sessions and, if so, what are its impli cations for long-term retention. In two studies with 3-month-olds, we found that (a) there is a delay between sessions after which the effec ts of successive sessions no longer cumulate, (b) when the second sess ion occurs nearer the end of the time window, retention is greater, an d (c) a memory can be reactivated only if the second session occurs wi thin the time window. These data further validate the time window cons truct and illustrate that the timing of a succeeding event determines whether it will be integrated with what came before or will be treated as unique. This result has major implications for the development of an individual's knowledge base.