Executive functioning has several definitions:

• It refers to mental processes that support the regulation of goal-directed behaviour.
• It refers to psychological processes involved in the conscious control of thought and action.
• It refers to top-down mental processes needed when you have to concentrate and have to pay attention.

It typically involves working memory (1), inhibitory control (2) and mental flexibility (3). Planning (1), decision making (2), judgement (3) and self-perception (4) are results of executive functioning.

The prefrontal cortex is imperative for executive functioning. However, it is likely that mainly the interactions with the prefrontal cortex are essential for executive functioning. According to Luria, the prefrontal cortex consists of interactive functional systems and this involves the integration of subsystems. The subsystems have specific roles but cannot be considered outside of the larger systems. This means that executive function may be a function and not a mechanism or cognitive structure. Functions refer to behavioural constructs defined in terms of their outcome (i.e. what they accomplish).

Executive functions are conscious processes but can get better with practice. They are influenced by individual differences in intelligence (1), motivation (2) and education (3). Executive functioning changes over the life course. It improves radically over the first few years and continues to improve in adolescence. Moreover, executive functions can be trained.

There is a continuum between cool and hot executive functions. A task where no emotions are involved and which is purely cognitive is a cool executive function task. Cool executive function is elicited by abstract, decontextualized problems.

This is a requisition for how one performs on hot executive functions. Hot executive function is required for problems that are characterized by high affective involvement or demand flexible appraisals of the affective significance of stimuli. A task where social evaluation plays a role and a reward or something else is at stake is a hot executive function task. Hot executive functions are often reported and not tested directly whereas cool executive functions are tested in a lab environment.

Updating refers to updating and monitoring information. This is a task of working memory. Shifting (i.e. cognitive flexibility) refers to switching between tasks or mental sets. Rule use includes error detection and error correction. A mistake in rule use could reflect either and it is often difficult to distinguish from one another. Representational inflexibility refers to the inability to form a new plan. Lack of response control refers to the inability to carry out a new plan.

Inhibition refers to the suppression of responses and this is an active process. It consists of two parts:

• Interference control
  This refers to controlling the interference (e.g. staying focused on a task) and makes use of selective attention and cognitive inhibition.
• Behavioural inhibition
  This refers to suppression of responses.

It is hypothesized that executive function only reflects inhibition. However, this is problematic for several reasons:

• Inhibition difficulties depend on the situation (e.g. A-not-B task or card sorting task).
• Inhibition is not a unitary construct (i.e. it consists of multiple parts).
• Inhibition may be too simple to capture everything covered by executive functions (e.g. planning with minimal inhibitory demands).
• Inhibition does not explain why correct responses are issued but only why actions are not executed.

It is more likely that inhibition is a necessary but not a sufficient aspect for executive functioning.

The delay of gratification test (i.e. marshmallow test) is intended to measure self-control and behavioural inhibition. This is believed to predict later life outcomes (e.g. academic outcomes). The longer a child can wait before receiving a reward, the better later life outcomes. However, this predictive value decreases when one controls for the child’s background (e.g. family income; mother’s education) and the child’s cognitive skills at preschool.

It is possible that this test does not only measure delay of gratification but also measures intelligence of cognitive skills and this may explain the limited replication of the results and the predictive value of the test. Intelligence and cognitive skills may explain both the preschool inhibition and the later life outcomes though the background factors could also explain both. It is also possible that the interaction between the background factors and the intelligence and cognitive skills explains the results.

Baddeley’s model on working memory states that there is a central executive which gives directions to the visuospatial sketchpad, the episodic buffer and the phonological loop. The visuospatial sketchpad is used to make meaning of visual information whereas the phonological loop is used for language. The episodic buffer regards the interaction between these two and is associated with long-term memory.

The phonological loop refers to the place where verbal information is stored. It has a limited capacity and depends on verbal rehearsal. The phonological similarity effect refers to an improved phonological memory for things that are more similar (e.g. words that sound more similar). The effect of word length refers to the fact that shorter words are easier to remember than longer words. The effect of prohibition of pronunciation (i.e. effect of impossibility of pronunciation) refers to the effect that information that can be verbalised is easier to remember.

The visuospatial sketchpad is the memory storage for visual information. It has limited capacity. Contrary to the phonological loop, there is simultaneous processing. The episodic buffer integrates multimodal information including information from long-term memory. Long-term memory contains more and more information with development, making working memory more and more effective with development because there is more long-term memory to fall back on.

The dimensional change card sorting (DCSS) task requires children to adapt to a changing environment and switch between rules. Children are told what to do at each trial and have to sort the card by feedback (e.g. after each card the instructor will tell them whether it is correct). After a number of correct trials, the sorting rule changes.

Perseveration refers to adhering to an old rule despite having knowledge of a new rule. Shifting (1), flexibility (2), inhibition (3), working memory (4), selective attention (5) and the degree to which complex rules can be followed have been used to explain preservation in the DCSS. However, it is difficult to separate components of executive functioning in a task because most are used simultaneously and are integrated.

Executive function development is associated with prefrontal cortex maturation. Damage to this brain area is characterized by problems with making decisions. However, the effect depends on the age at the time of the lesion. Moreover, damage to this brain area does not necessarily mean executive function impairment. Behavioural impairments as a result of prefrontal cortex lesions may occur later in development when late-developing functions would normally appear. The consequences of prefrontal cortex lesions are often less noticeable in children than in adults.

The prefrontal cortex is the youngest brain area and most vulnerable to the effects of ageing. There is a rapid development in this brain area between birth and about two years. The next growth spurt is between 4 and 7 years. It continues to develop into adulthood.

The lateral prefrontal cortex may play an important role in the integration of sensory and mnemonic information and the regulation of intellectual function and action. Dopamine may play an important role in this brain area. The ventral and medial prefrontal cortex consists of ventral and medial regions of the prefrontal cortex. It has strong connection to the amygdala and other parts of the limbic system. It is involved in the integration of affective and non-affective information and for the regulation of appetitive and motivated behaviour.

As working memory develops, capacity (1), duration (2), knowledge (3), processing speed (4) and strategies (5) develop. Working memory, shifting and inhibition often go together. This is because it is important to keep the goal in mind while attempting to inhibit a response. Shifting appears to develop up to 15 years and working memory develops until 21 years of age. Changes in working memory may be the result of increases in the capacity of the working memory. This may mean that the development of executive function is the result of increases in strength of active memory representations which allows children to override prepotent tendencies mediated by latent memory traces.

The cognitive complexity and control theory states that age-related changes in executive function are the result of children’s increasing ability to use more complex rule systems. To increase the complexity of the rule systems, reflection is necessary and this typically develops during the preschool years.

In the problem-solving framework, executive function is believed to proceed from problem representation (1) to planning (2) to execution (3) to evaluation (4). Inflexibility can occur at each of these stages:

1. Problem representation
   Children become better in both hot (e.g. theory of mind measures) and cold (e.g. flexible restructuring of the problem representation) executive functions with age.
2. Planning
   There are developmental changes in problem analysis and depth of search for a solution.
3. Execution
   Children of 2.5 years old make perseverative errors. Three-year-olds have difficulty integrating incompatible pairs of rules into a single system via higher-order rules despite having knowledge of the rules. Children may be better at a hot executive function task when they convert it into a cool executive function task.
4. Evaluation
   This includes error detection and error correction. It is possible that error detection develops before error correction.

Three-year-olds typically have difficulty regulating approach behaviour in motivationally significant situations but are capable of adaptive decision making. Self-regulation may be facilitated by adopting a third-person perspective of one’s behaviour. It is likely that the phases of the problem-solving framework develop together. Hot tasks of executive function may be more difficult than cool tasks if task difficulty is equal.

The structure of executive functioning can be studied using confirmatory factor analysis (CFA). This means that each component of executive functioning is a latent variable that is measured with a manifest test. The relations between the functions reflect what tasks have in common. The interpretation of factors is not always easy as the factors could be separated but still correlated.

Different factor analytic studies have found different components of executive functioning while some studies did not find different components (e.g. inhibition not being internally consistent with the factor model) or found a single component of executive functioning (i.e. only one factor explaining all the results). These contradictory results may be explained by the age of people when they do different tasks (1), the way the tasks are scored (2) and because of the selected tasks (3). The selected tasks may rely on task-specific networks and not on general executive functioning factors. The tasks may not be pure measures of individual factors of executive functioning.

Executive function suffers from stress. In a classroom, executive function is addressed during cooperation (1), using scarce material (2), self-regulated learning (3) and pretend play (4). Extracurricular activities could promote executive function. For example, sports (e.g. martial arts) ask for selective attention but does this in a fun way.

By using children with the poorest executive functioning, training the most difficult tasks seems to have the greatest benefit on their EF. However, this may be regression to the mean. It is possible that children who participate in sports which promote executive functions have a higher SES or already have a greater executive function. It is thus not clear whether sports clearly influence executive function.

The home environment promotes executive function through maternal sensitivity (1), maternal mind-mindedness (2), maternal autonomy (3) and maternal scaffolding (4). These factors also promote child cognitive ability. There is a bidirectional relationship between executive functions and a child’s cognitive ability.

To promote executive function, it is good to provide opportunities to practice executive functions (1), talk about the mind (i.e. mind-mindedness) (2), use scaffolding (3), provide tools (4) and investigate whether social or emotional problems prevent the child from using executive functions (5).