Integrated Calendar

Recalling unrelated memory items is a challenging task for most people. In the classical free recall paradigm, participants are asked to repeat a list of randomly assembled words in an arbitrary order. For lists as short as five words, people begin to make recall mistakes, and for longer lists the fraction of recalled words is steadily decreasing. The variability of recall performance across participants is very large, but its origins, and in particular the potential contribution of practice, are not clear. In this study, we explored whether more and less successful participants exhibit different patterns of recall and whether this pattern changes over the course of the experiment. To this end, we analyzed a large data set of immediate free recall collected in the lab of M. Kahana (UPenn). We found that some participants exhibited extremely high recall performance, including many trials where they recalled completely the full presented lists of 16 words (‘perfect trials’). Moreover, these trials were typically characterized by a robust application of input-position dependent recall strategies; most prominently a serial ordering or a number of chunking strategies where presented lists were recalled in groups of consecutively positioned words. The number of perfect trials increased dramatically with practice, accompanied by a general increase in the extent of positional grouping applied by participants; however the choice of a particular strategy and the time course of its acquisition were highly variable among participants. Our results show, for the first time, that practicing memory recall results in improved performance, and that there are multiple ways humans can adopt to achieve perfect recall.