Donders Institute for Brain, Cognition and Behaviour
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Thesis defense Loes van Aken (Donders series 263)

12 mei 2017

Promotor: prof. dr. J. Egger, prof. dr. R. Kessels

The relationship between intelligence and executive function: Understanding theory in clinical practice

Well over a century after Francis Galton and a hundred years after the first Stanford-Binet test, researchers still haven’t reached consensus on what intelligence exactly is. Nevertheless, the concept of intelligence is frequently used in many ways and definitions are legion. In clinical practice, numerous patients are tested with instruments to assess intelligence on a daily basis. These intelligence tests are often part of more extensive neuropsychological assessment. With these assessments, clinicians examine information processing -also called cognitive functioning- in order to explain behavioural disorders in their patients. In neuropsychology, cognitive processes that are involved in complex or ‘intelligent’ behaviour are called executive functions.

Interestingly, development of intelligence tests does not follow neuropsychological theory on complex behaviour and information processing. Instead, intelligence tests describe a construct that is not based on theory, that is, a construct that is purely derived from empirical data and observations. Using this line of reasoning, the concept of intelligence is nothing more than what is measured with the intelligence test.

The current research demonstrates great overlap between intelligence and executive function on a conceptual level. However, the coherency between tests of intelligence and executive function is considerably less clear. Furthermore, current intelligence tests present a one-sided view of intelligence in which executive processes are left out. The results plead for a renewed focus on theorization of intelligence, instead of additional empirical studies of the topic. This can also enhance test development and improve clinical assessment.