Executive Function

An Overview of Executive Functioning

Credit: Emerge Pediatric Therapy Opens in new window

Executive function is what controls the execution of complex, goal-directed activities. If a task requires numerous acts be taken in particular sequence in order to achieve success, executive function orchestrates that sequencing. When executive function is compromised one may witness manifestations of forgetfulness, disorientation and agitation.

Attention, on the other hand, is the cognitive ability to focus; to suppress extraneous stimuli and attend to that stimuli which is directly related to the task at hand.

Different Types of Executive Functioning

Research in the area of executive functioning has grown rapidly in recent years, both in the adult and developmental literatures.

One of the key issues to emerge is the belief that executive functions represent not just a single type of skill, but a number of related skills (e.g. Miyake, Friedman, Emerson, Witzki, Howerter & Wager, 2000). Therefore, within the broad domain of executive functioning there are, nevertheless, separate abilities that can be distinguished.

A recent twin study has provided support for this viewpoint. Friedman, Miyake, Young, DeFries, Corley and Hewitt (2008) showed that executive functions draw on a common factor that is highly heritable, arguing that this is why different measures of executive functioning are related to each other.

These authors also suggested that executive functioning is not simply another ability that can substitute for intelligence. Opens in new window. They have provided evidence that executive functions are not uniquely related to measures of intelligence, despite the fact that they are, nevertheless, responsible for much of what we might describe as intelligent behavior (Friedman et al., 2006).

One of the sub-skills in the executive functioning family of abilities has been identified as working memory Opens in new window, but the meaning of this term is rather specific. For example, Swanson (2006) defines working memory as:

a processing resource of limited capacity, involved in the preservation of information while simultaneously processing the same or other information. (Swanson 2006: p. 61)

There are several other skills believed to belong to the executive functioning family of abilities, and these will all be described in the remainder of this entry. However, an important point to reiterate before we do this relates to what brings together and unifies all executive functioning skills.

As we have already pointed out, this is what the central executive Opens in new window is designed to do, so the concepts of ‘executive functioning’ and ‘central executive’ are at the very least highly overlapping, although there are uncertainties about exactly how these concepts interrelate.

In the literature on executive functioning, some authors (e.g. Pennington & Ozonof, 1996) have suggested that executive functioning can be divided into five or six discrete sub-skills. This division is often referred to as the fractionation of executive functioning.

Box 1-X describes the main areas of executive functioning identified in the literature.

Other authors have suggested that there is good evidence for three sub-skills of executive functioning: inhibition, working memory and set shifting. There is a reasonable amount of evidence in children and adults for the existence of these factors (Bryson & Smith, 2008). However, not all of the evidence is entirely consistent, particularly for children.

Another point to emphasize is that several of the aforementioned studies did not look for more than three factors, so this figure may be arbitrary.

Another key point that has emerged from the literature is that, whilst we can divide executive functioning into a number of distinct sub-skills, these skills are still loosely related to each other.

Again, the evidence is not entirely consistent, but there is reasonably consensus that the sub-skills of executive functioning measure broadly the same types of abilities in relation to the control and regulation of behavior during complex, novel tasks (Miyake et al., 2000).

There are a wide range of tasks that have been used to assess executive skills. These areas include:

• executive-loaded working memory,
• inhibition,
• set shifting, planning,

• fluency,
• dual-task performance and
• random generation.

Some of these tasks have traditionally been used to study executive skills within the working memory Opens in new window domain, whereas others have been regarded as measuring executive functioning more broadly.

This comprehensive approach has been taken to try to gain a greater understanding of executive control in typical and atypical development. However, please bear in mind that there are still uncertainties with respect to the relationships between the central executive and executive functioning in its widest sense.

There is also the issue of exactly how these systems might be limited in terms of capacity, although it is clear that such capacity limitations do exist (e.g. Swanson, 2006).

In the next entry Opens in new window brief overviews will be given of each sub-skill of executive functioning listed earlier.