The list length effect in short-term memory

Abstract

In free recall, the list length effect (LLE) refers to the finding that the proportion of correctly recalled items decreases as set-size increases but at the same time the total number of recalled items continues to increase with set-size (Murdock, 1962). Oberauer et al. (2018) proposed that a decrease in memory accuracy as a function of increasing set-size was fundamental to conceptualizations of short-term and working memory. Evidence of a LLE in short-term/working memory would contradict this benchmark. Beaman (2006) observed a LLE in serial recall whereas Unsworth and Engle (2006) observed no such effect in either serial recall or complex span. In the current research, we sought to reconcile these conflicting results. Six experiments were conducted, examining the relationship between the number and proportion of words recalled in both serial recall and complex span. No LLE was observed in either task. Instead, the proportion of words recalled decreased as a function of list length, while the number of words recalled initially increased, before either reaching a plateau or decreasing. The results suggest that recall accuracy decreases as a function of increasing list length due to increased interference and decreased positional and temporal distinctiveness in longer lists.