The fluctuation of IQ

Intelligence is often thought to be fixed across the lifespan, and IQ scores are used to sort children and adolescents for educational purposes. But in fact, IQ fluctuates, and individuals can be trained to perform better on IQ tests, indicating that sorting on this basis may not serve any useful purpose.

Intelligence is typically measured with standardised verbal and non-verbal reasoning tasks, providing an intelligence quotient (IQ) score that takes account of age. This score is thought to reflect a range of cognitive skills that indicate an individual’s learning aptitude. It is often assumed that IQ is stable across life, with some individuals having higher intelligence than others. These scores are sometimes used to determine a child’s entry to school or a teenager’s place at university, seemingly demonstrating the individual’s ability to achieve.

However, individual IQ scores actually fluctuate, with changes in the brain’s structure and function mirroring changes in IQ. This means that if a child is top of their class on an IQ test at age 11, by the time they are 16, this may no longer be the case. And yet 164 UK grammar schools and many private schools select children on the basis of reasoning (and sometimes maths and English) tests for entry at age 11.

Studies with children, adolescents, and adults, have shown that performance on IQ tests can improve with training, further demonstrating that these tests do not measure an underlying fixed ability. Generally the participants in these studies have got better at the task they were trained on, with some transfer to similar tasks, but no transfer to dissimilar tasks (a pattern like the one typically observed following executive function training).

“Those families who cannot afford the extra lessons may miss out on the opportunity to send their child to their desired school.”

This further calls into question the decisions of schools and universities to determine entry based on performance on these tests. Those who have practiced and received tuition are likely to perform better. Concerningly, it is likely that those who can afford it will pay for tuition in order to get their child into their school of choice. Those families who cannot afford the extra lessons may miss out on the opportunity to send their child to their desired school.

This is all the more disheartening when it is possible that, given the lack of transfer, the training may not even have an impact on school- or university-related abilities or final grades. Further research is needed to investigate the extent to which performance on entrance tests relates to later exam performance, and whether or not those who received initial training do indeed perform better later on.

“The sorting of children according to test performance, regardless of the utility of this approach for determining their learning capacity, may have negative consequences.”

The sorting of children according to test performance, regardless of the utility of this approach for determining their learning capacity, may have negative consequences. Those children who do undergo additional tuition are spending time away from other activities which may be more fulfilling. Children who take the test may feel anxious about their performance, and may then be sorted into a different school from their friends or siblings, potentially leading to loneliness. Those who are not selected for the school they want may also lose confidence in their ability to perform well.

Given these possible outcomes, and considering the need for more research, conversations about why this testing exists and what it seeks to achieve must continue.