executive functions

The term executive functions appears in many psychological contexts. Among other reasons, this reflects the fact that the term refers to a conglomerate of individual terms. Executive Functions summarizes several controlling, maintaining and updating skills that are assigned to the frontal brain. In our everyday life, we would most likely use the term “self-regulation” to describe what is known as shifting between task sets, updating of working memory representations and inhibition of dominant responses (Hofman, Schmeichel & Baddeley, 2012) in psychological research. The reason why these three concepts are all called executive function results from their significant overlaps in variance. However, shifting and updating have an additional unique proportion of variance that cannot be explained by the common executive function. On the contrary, inhibition overlaps with both other concepts to such an extent that no specific component remains. This pattern can be described in the terms of unity (the common executive function) and diversity (the unique parts of shifting and updating).

The underlying structure of executive functions has been assessed with individual task paradigms. Letter-memory tasks can be used to assess updating. In these tasks, a letter is presented serially and must be combined together with the two previous letters so that the content held in working memory is constantly updated (Miyake et al., 2000). For shifting tasks, the task switch paradigm is mostly used, which requires the test person to alternate between two different tasks. Here, it can be seen that a switch trial leads to a longer reaction time than when the same task appears twice in succession. This increase in reaction time in a switch trial is interpreted as the time it takes to change the mental task set to match the current task demands. To measure inhibition, the basic idea is to expose subjects to a stimulus that triggers an automatic response and has to be suppressed to complete the task successfully. One well-known implementation of this paradigm is the Stroop task. During this test subjects are required to name the color of a written color word instead of reading the word (if the word blue is printed in green, the correct answer is green). This requires inhibition of the automatic reading of the color word (Sugg & McDonald, 1994). Other paradigms that can be used to assess inhibition use antisaccades. In antisaccade experiments, subjects are equipped with an eye tracker and instructed to look away from a given emergent stimulus (Miyake et al., 2000). However, despite these tasks that are meant to draw conclusions about the executive functionality of one person, most tests may also require a certain level of cognitive control, which may be the reason why executive functions are also mentioned in the context of psychometric tests.

Moreover, executive functions are a well-known concept regarding several pathological states, too. Deficits in executive control are usually related to the frontal lobe and show substantial correlations to prefrontal cortex volume (Yuan & Raz, 2005). In addition to frontal lobe damage, there are other neurocognitive diseases, such as Parkinson or Alzheimer┬┤s that are related with executive dysfunction. Referring to a meta-analysis from Kudlicka, Clare and Hindle (2011), executive dysfunction is evident in Parkinson’s disease, although the structure of the impairment is not yet clear. Regarding Alzheimer’s dementia, it is known that the Stroop Task can successfully differentiate between healthy individuals and AD patients (Guarino et al., 2019). In conclusion, executive functions are a highly relevant concept that is often investigated in cognitive psychology and one of the key symptoms in various pathologies.