Executive function

Diamond's review describes executive functions as what makes it possible to play with ideas mentally, take time to think before acting, meet new and unexpected challenges, resist temptations and stay focused [1].

Inhibition and cognitive flexibility each cover several skills [1]. Inhibition includes response inhibition (self-control) and interference control, which in turn includes selective attention [1]. Working memory means holding information in mind and working with it [1]. Cognitive flexibility, also called set shifting, includes adapting quickly and flexibly to changed circumstances [1].

The parts are linked but not identical. In a study of 137 college students, three often-proposed functions (shifting between mental sets, updating and monitoring information, and inhibiting dominant responses) were moderately correlated with one another but clearly separable [2]. The same analysis tied complex tasks to different functions: the Wisconsin Card Sorting Test related most strongly to shifting, and the Tower of Hanoi to inhibition [2]. The authors called this the unity and diversity of executive functions [2].

Diamond also notes that stress, lack of sleep, loneliness or lack of exercise each impair executive functions, and that they can improve with practice [1].

Because executive function is a family, a trial's "executive function" result may come from a single task or from a composite score built from several. Check which tasks went into it. The core functions are related but separable [2], so a change on one task does not show a change on the others.

On NootropicsWork, executive function is graded as its own outcome. Working memory has a separate outcome, and attention switching, a task-switching measure of cognitive flexibility, is graded separately too. A trial might report a change in task switching but none on other executive tasks; that is reported as a task-switching finding, compared with placebo.

Working memory, attention and cognitive load.