Monday, December 2, 2013

Executive Functions: Inhibitory Control, Working Memory, and Cognitive Flexibility

Diamond, A. (2013). Executive Functions. Annual Review of Psychology, 64, 135–168.

Diamond refers to executive functions (EFs) as a “family” of mental processes necessary for concentrating or paying attention. In this review paper, Diamond walks through three core EFs: inhibitory control, working memory, and cognitive flexibility.

Inhibitory control is our ability to choose what to focus on while suppressing distractors or impulsive behaviours. Aspects include using self-control, staying on task, resisting temptation, and delaying gratification. These aspects can be assessed using a variety of behavioural measures. One example of a delayed gratification test is the marshmallow test, in which children are asked to choose between receiving one marshmallow now or two marshmallows if they wait.

Working memory, the ability to manipulate verbal or nonverbal material while holding it in mind, tends to work closely with inhibitory control. For example, working memory supports inhibitory control by holding the current goal in mind, which makes it easier to stay on task. Similarly, inhibitory control can support working memory by suppressing irrelevant ideas and decluttering our mental workspace. This overlap can make it difficult to separate working memory and inhibitory control, although some research with older adults is showing that the ability to suppress unwanted ideas or actions (i.e., inhibitory control) is separate from the ability to activate appropriate ideas or actions (i.e., working memory). Diamond notes the difficulty in assessing working memory, arguing that many tasks assess only the storage of information, whereas others go beyond the scope of working memory and require more subcomponents of EFs.

Cognitive flexibility allows for mental adaptability and versatility, such as thinking “outside the box,” seeing something from a different perspective, or switching tasks or priorities. A task commonly used to assess cognitive flexibility is a card sorting task. For this activity, subjects are given cards with images that could be sorted according to a few different features (e.g., colour of object , shape of object, background colour) and asked to sort them. Subjects may be asked to sort the cards based on trial-by-trial feedback they receive, or they may be asked to sort them according to one dimension first, and another later on.

Diamond notes that EFs are highly affected by stressors such as depressed mood, sleep deprivation, or insufficient exercise. She concludes by outlining five principles of effective intervention for EF: 1) those with lowest EF will benefit the most; 2) extent of transfer depends on the type of intervention; 3) demands on EF need to continually increase; 4) repetition is essential; 5) biggest differences between trial groups and control groups are seen on the most demanding tasks.

Blogger: Laura Pauls is a PhD student in Speech & Language Science, researching children with language impairment and/or working memory impairment.

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