Neurotic people score lower on intelligence tests, research finds.
However, the link could be down to the neurotic being nervous while taking tests, some psychologists think.
The links have been found between higher neuroticism and lower full-scale intelligence and lower verbal IQ.
Neuroticism is a personality trait that is strongly linked to anxiety, sadness, irritability and self-consciousness.
The study’s authors explain the personality trait of neuroticism:
“Neuroticism reflects a tendency to experience negative emotions, like anxiety and depression.
The six sub-facets of Neuroticism, according to Costa and McCrae (1992) are Anxiety, Anger-hostility, Depression, Self-consciousness, Impulsiveness and Vulnerability.
High scorers tend to be sensitive, emotional, worrying, moody, frequently depressed, often sleep badly and may suffer from various psychosomatic disorders.[…]
Low scorers tend to be secure, hardy and generally relaxed even under stressful conditions.”
The conclusions come from two studies.
In the first, 646 Dutch twins were given personality and IQ tests.
The researchers found the link between higher neuroticism and lower IQ, concluding that the link was mostly explained by genetics.
The second, though, gave 213 people IQ tests and divided them into two groups based on their anxiety.
The authors explain that neurotic people got more nervous when taking the test:
“…high Neurotics are more stressed under testing conditions than low Neurotics, and that they are even more stressed when they receive information which induces further anxiety.”
The researchers were then able to statistically remove the effects of anxiety on test-takers.
Then, neurotic people did just as well on the IQ test as non-neurotic people.
The authors conclude:
“Neurotics become more anxious under testing conditions, and this anxiety affects their performance on the IQ tests.
It is therefore proposed that Neuroticism is not related to intelligence per se, but to intelligence test performance, which has been proposed in the past (Eysenck, 1971).
This suggestion implies that IQ tests may underestimate the true intelligence of Neurotic individuals.”