From primed to learn: the saturation of repetition priming and the induction of long-term memory

Although practice can make perfect, it is not clear how much practice is needed to trigger long-lasting performance gains on a given task. Here, using a letter enumeration task, we show that the transition of experience dependent performance gains to a relatively stable form, as well as the triggering of delayed, long-lasting, between session gains (both effects are considered manifestations of consolidation processes) is amount-of-practice dependent. We then show (a) that consolidation processes, once triggered, can proceed without further practice as a function of time and (b) that the triggering of consolidation processes is related to repetition priming effects--performance gains in processing a previously experienced item. However, we show that repetition priming effects saturate after a limited number of consecutive repetitions and reflect an initial, but potentially reversible, response to the repeated experience. Moreover, we show that one critical parameter determining the occurrence of repetition priming (but not skill learning) is the presence of interference (by a somewhat different set of items) prior to the primer presentation. Thus, our results suggest that the saturation of repetition priming effects, rather than priming per se, may be critical to the induction of slow learning processes and consolidation.