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.