Sequential Difficulty Effects on Task Performance: Pervasive, Persistent, and Protean

Abstract

Difficult cognitive tasks tend to be performed less quickly, less accurately, and recruit more neural activity than easier tasks. But how do difficulty effects carry over from one trial to the next? Does the prior effort over-extend our working memory capacity or other cognitive resources? Or can an earlier challenge better ready us to meet the next one? Previous research examining such sequential difficulty effects (SDEs) with instructed strategies suggests impaired performance on trials following a difficult trial. Conflict monitoring studies, in contrast, find enhanced performance on trials following a difficult trial. Yet little is known about whether and how difficulty carries over to subsequent tasks when (a) difficulty arises from a participant’s spontaneously adopted processing approach, (b) there is no direct response conflict, and (c) tasks are complex, as opposed to relatively simple. In a series of four studies designed to address these gaps, we examined SDEs in three tasks: complex metaphor comprehension, complex spatial reasoning, and simple number comparison. On both the metaphor and spatial reasoning tasks, a post-difficulty slowing effect was observed. Further analyses newly revealed that these SDEs can accumulate, with performance continuing to slow with increasing numbers of previous difficult trials, perhaps reflecting working memory or other capacity limitations or perceived disutility of further effort. In contrast, we found that prior difficulty boosted performance on subsequent trials in the simple number comparison task, perhaps reflecting heightened precision of attention. These results show that the carry-over effects––sometimes detrimental, but sometimes beneficial––of level of difficulty vary depending on the complexity of the task and its demands on working memory and/or the expected value of sustained effort. Furthermore, beneficial carry-over effects can be observed when there is no direct response conflict or effects thereof. Collectively, the findings provide compelling evidence for the generalizability of SDEs. Such effects span verbal, visuo-spatial, and numerical domains, with potential implications for test and performance evaluation, educational design, perceptual change detection, optimizing mental agility, and the sequencing of activities in our professional and personal lives.