Inhibition, shifting and updating in relation to psychometric intelligence across ability groups in the psychiatric population.
K E Biesmans, L van Aken, E M J Frunt and 2 others
PMID 30403315WHAT IT FOUND
Executive-function scores and IQ were related, but the expected stronger link in lower ability groups was not found.
Shifting was related to IQ only in normal/high ability patients. In people with intellectual disability, scores may reflect processing speed rather than a specific executive deficit.
Key findings
01In the whole sample, executive-function scores and IQ correlated significantly. The combined executive-function score shared 25.2% of variance with IQ, and inhibition, shifting and updating shared 13.7%, 22.8% and 11.3%, respectively.
02The separate executive-function correlations with IQ did not differ significantly across ability groups. A combined executive-function score did differ across groups, and the group effect was significant for shifting only; shifting was significantly related to IQ only in the normal/high intelligence group.
03Within the groups, executive-function correlations with IQ were significant in the normal/high group for composite executive function, inhibition, shifting and updating, and in the borderline group for composite executive function and shifting; none was significant in the mild intellectual disability group.
STILL TO COME
How it was doneWhat they found
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What it does not show
The sample was heterogeneous, with complex psychiatric diagnoses, and results could be influenced by condition severity, medication or other health problems. The ability groups were split by IQ cut-offs that the authors called arbitrary, and group sizes were very unequal (32, 78 and 140). IQ scores came from three different tests and were merged into one variable, which may not be ideal for comparing individuals. Power was regarded as insufficient for the within-group correlations and analyses of covariance, so the group results are preliminary. Executive-function tasks are not pure measures; scores can be influenced by processing speed, reading, attention and other basic cognitive processes, especially in people with intellectual disability. Eleven extreme cases were removed, and variance was not equal across groups for shifting and IQ.
Declared interests
The authors declared no conflict of interest.
The easy way to misread this
Do not conclude that executive-function test scores prove a specific deficit in inhibition, shifting or updating in patients with intellectual disability. In this sample, task scores may also reflect processing speed and other basic cognitive demands. The within-group analyses were called preliminary because power was insufficient.