Intelligence tests and the individual: Unsolvable problems with validity and reliability

IQ scores are used in the Netherlands to determine whether an individual qualifies for special education or has access to healthcare. The term for this use of IQ is referred to as “slagboomdiagnostiek” (doorway diagnostics). Criticism has been voiced from the professional field regarding this policy. In this article, we will discuss whether the current Dutch policy is justified by examining the validity and reliability of IQ tests. Specifically, we will address whether the IQ test can be used in clinical decision-making regarding the individual. We argue that while the validity and reliability have been demonstrated at a group level, they do not hold true for the individual, leading to the conclusion that the current Dutch policy is not justified.