Personality Type and Intelligence

Is there a relationship between your personality type and how you score on an IQ test?

The study of personality and intelligence share a number of important factors. The overriding one, perhaps, pertains to the sphere of behavioural genetics, the study of the heritability of human behaviour.

What do we mean by heritability?

The term heritability is an awkward one and the subject of much confusion. Geneticist Adam Rutherford has described the term heritability as both a tricky idea and a hideously named thing, mainly because it sounds a little bit like inherited and this leads to untold confusion.

Heritability is a measure of how much of the difference we see in a population can be accounted for by genetics and how much is determined by the environment. It’s not just about genes and it’s not just about the environment. It is about populations and not about individuals.

It’s obviously much more complex than this, and I would certainly refer you to Rutherford’s excellent book for a more in-depth analysis.

Personality and intelligence researchers use a number of different methods in the search for some quantifiable measure of inheritance, but they tend to favour twin studies above all others because of the degree of genetic similarity.

That said, a 2008 study found that, contrary to what is generally agreed, identical twins might not be exactly genetically identical after all, making twin studies that little bit harder.

We can study many sets of twins and measure a number of factors such as IQ and personality traits and then examine the relationship between them. Behaviours geneticists don’t study genes per se (that unenviable task is left to the biologists), what they do is look for correlations between variables (e.g. twins and IQ; IQ and personality traits; twins and personality traits, and so on).

We can. therefore, examine both the heritability of Big 5 traits and their relationship to other factors. I’ve previously discussed the relation between specific traits and academic achievement, but what about psychometric intelligence, or IQ? Are there any traits that enhance it and are their any that inhibit it?

General Findings.

Studies have found that the trait most strongly correlated with IQ is Openness to experience, a trait that is associated with a wide collection of intellectual orientated behaviours such as curiosity, creativity and the willingness to explore new ideas.

Research relating to extraversion is more complex, often finding mixed and negative relationships.

Interestingly, conscientiousness is slightly negatively correlated with IQ, leading some researchers to suggest that it’s a trait that less intelligent individuals can possess as compensation (e.g. Moutafi et al., 2006). Conscientiousness, therefore, compensates for lower levels of intelligence.

How Do Traits Impact IQ?

The basic premise is that certain traits and states can affect the reliability of IQ scores.

By states, we are mainly discussing emotions and mood, but we could also include other factors such as illness or fatigue. Some studies, for example, have found that the time of the day the test is taken can impact the results.

Indeed, three trait models (Big 5, Gigantic 3 and 16PF) have all found that personality can tentatively predict IQ, even though some traits are more predictive than others.

Traits may, therefore, impact IQ scores in different ways.

A 1997 meta-analysis found that neuroticism negatively impacts IQ scores, as did extroversion. While studies relating to extroversion are often mixed, those related to neuroticism are generally consistent.

Neuroticism, Test Anxiety and IQ.

Trait anxiety, that is, chronic anxiety, has been linked to poor performance under exam conditions.

This isn’t new, having been identified by Callard and Goodfellow back in 1962. There are, however, some curious difference within groups, with a positive relationship associated with higher IQ groups and a negative relationship with low IQ groups.

Despite this, other studies (e.g. Kalmanchey & Kozeki, 1983; Furnham, Forde and Cotter, 1998) have concluded that intelligence decreases with negative affectivity (such as anxiety, worry, tension, depression and anger). These are relatively consistent finding, regardless of the particular cognitive ability test used or personality model adopted.

Are neurotic individuals, therefore, less intelligent?

People who score higher on levels of neuroticism are therefore more likely to score lower on tests of IQ.

Does this then mean that anxious people are less intelligent?

The problem is that the negative consequences associated with individuals scoring high on levels of neuroticism include mechanisms that interfere with cognitive processing, including memory and attention, and these processes are needed to solve cognitive ability tests (or IQ tests).

Hembree (1988) found a moderate to high correlation between trait & test anxiety and IQ performance & test anxiety. What this means is that people with high trait anxiety are more likely to suffer from test anxiety which consequently negatively impacts IQ scores. This certainly makes intuitive sense.

Test anxiety is usually thought of as a type state anxiety, that is, it’s about being currently anxious rather than chronically anxious, although Hembree suggests that these may be very closely related. In other words, neurotic individuals who experience trait anxiety are much more likely to also experience state anxiety.

This negative relationship between neuroticism and psychometric intelligence performance is most likely related to the anxiety components of the neuroticism scale (such as worry). This then impairs functioning on IQ tests and other high stakes or competitive formal assessments.

Neuroticism, IQ and Self-efficacy.

Mueller (1992) proposed a theory whereby neuroticism is associated with levels of self-efficacy (our belief in our ability to complete a given task or reach a pre-determined goal) but not of intellectual competence so that high trait anxiety results in lower level of self-efficacy. These feelings of self-efficacy then may lead to worry. Worry then impairs test performance through test or state anxiety.

Anxiety then makes it less likely that the individual will invest time in preparation or engage in intellectually stimulating activities. This results in lower engagement and lower intellectual competence. Low feelings of competence then feed back into fears surrounding test performance, resulting in more anxiety, in a never-ending cycle.

What does all this really tell us?

Predicting performance from state anxiety is highly problematic due it only arising in specific circumstances. It’s highly likely, however, that those individuals with trait anxiety will also suffer from specific task-related anxiety so it would be more useful to predict outcomes based on neurotic components observable in the individual. These can then be tackled at a much earlier stage.

Of course, in education we neither test for personality or IQ (and I think there are many good reasons why we don’t), so we might conclude that knowing that trait anxiety can lead to lower scores on IQ tests creates little real-world advantage. However, high-stakes testing can be viewed in the same situational light as IQ testing and teachers tend to be able to identify those students who are more generally more anxious.

The link between IQ and anxiety further highlights the need to identify and assist high-anxious students at an early stage before a potentially damaging cycle can take hold.