Precursors to Chunking Vanish When Working Memory Capacity is exceeded

Abstract

It is known that working memory capacity is limited. But what exactly happens if it is exceeded? Is the excess simply dropped or does it affect the items that are within the capacity of working memory? Here we show that as the capacity of working memory is exceeded, a rudimentary type of learning vanishes, namely, the probability of pairing items in the order of presentation. Free recall of 500 Russian college students was measured using the Tarnow Unchunkable Test (Tarnow, 2014) consisting of sets of 3 and 4 double digit items. The average working memory capacity is exceeded with four items. In the three item test, even though items were constructed to be unchunkable, there were asymmetric associations: recalling item N was more sensitive to whether item N-1 is recalled than the other way around. These asymmetric associations are presumably precursors of \"chunking\" and learning. The asymmetric associations between items 1 and 2 and items 2 and 3 were similar. As the working memory capacity is exceeded in the four item test, the asymmetric association for the subject group halved from item 1 to item 2 (p=0.32) and disappeared completely from items 2 to 3 (large effect size: {eta}2=0.79, p=0.001) and there were no asymmetric associations from items 3 to 4.