It has been usual in much of the history of the psychology of individual differences to deal with intelligence and personality in different chapters. Intelligence is about abilities and skills, personality is about emotions, attitudes and behavioural preferences.
Intelligence has one main score, g, and three or four component and subsidiary scores, such as verbal, arithmetical, spatial and processing/memory. You have to take an actual test, and will eventually start to fail items that are too hard for you. No wonder these tests generate visceral reactions. Self rating of genius is not allowed: you have to prove every ability with correct answers.
Personality has five main scores: neuroticism, extraversion, openness to experience, agreeableness and conscientiousness. These were called the Big Five, and represented something of a truce between those who favoured 3 factors and those holding out for 16 factors. Science progresses, but slowly. You have to take a personality test, but you are told “There are no right or wrong items” and there is nothing to prove. This liberal approach generates far less animosity in the general public. Yet, a moments thought about living with people confirms that some are easier to get on with than others. At the very least, ticking a box which says “I don’t particularly care what happens to other people” should raise a scintilla of doubt about whether they would be an agreeable companion on a difficult journey. Some items must be “wrong” in a social sense.
Happily, this obvious point has occurred to brighter minds (Rushton and Irwing, 2011) , who have factor analysed the five factor model and shown that it can be reduced to one dimension: the General Factor of Personality. High scores on this General Factor of Personality indicate a “good” personality; low scores a “difficult” personality (someone who is hard to get along with). Individuals high on the General Factor of Personality are altruistic, agreeable, relaxed, conscientious, sociable, and open-minded, with high levels of well-being and self-esteem. Those with poorer personalities are at the other end of the descriptive spectrum. They would tend to be selfish, disagreeable, anxious, not dependable, unsociable, closed-minded or rigid thinkers, with high levels of distress and low self-esteem.
We are always at liberty to name factors as we wish, and to my mind this could also be labelled “Easy to get along with” versus “Difficult and un-cooperative”. Mind you, not everyone agrees with this simplification. I regard it as performing a public service, in that it ought to help us avoid vexatious people.
To what extent is personality (as one factor) correlated with intelligence (as one factor)?
Before answering this question, we must note a curious feature of personality assessments: they are all based on self report. Are you a kind and good natured person? I am sure you are. However, I would be more convinced if your colleagues confirmed it privately, rather than that you asserted it on the basis of self-love and selective memory. These facts were borne in on me by many years of using the Belbin system, which seeks to find out what sorts of team roles people habitually adopt when working in groups. Individual self-perceptions were supplemented by at least 4 independent observers. I used to ask for at least 8 observers, who all sent in their observations privately to me. Self-perceptions very rarely coincided with observers’ opinions, (say only 15% of the time) and then usually only when the person concerned had a very clear team role preference. In the end, I only used observer’s assessments, and my clients preferred their feedback when seeking to understand themselves.
Self knowledge has limits. The energy we put into being ourselves reduces our capacity to monitor ourselves. Too much self-knowledge, too much of the time, might endanger our survival.
Curtis Dunkel from Western Illinois University has found a data set from Block and Block (2006) in which children’s personality was rated by assessors and intelligence was assessed concurrently. It is one of those treasure troves which permits interesting research. The sample size of 104 is pretty good bearing in mind they were followed from early childhood, and given face to face Wechsler Intelligence tests, the gold standard for intelligence assessment. Among other findings, the correlation between intelligence at 11 and 18 is an impressive 0.84
Dunkel finds that there is a significant association between intelligence and personality. Stable personality at 18 (as assessed by others) and stable g as derived from the Wechsler Adult Intelligence Test correlate at 0.46 which is substantial as well as being significant. It would seem that being brighter than average goes together with having an agreeable and conscientious attitude.
This puts the cat among the pigeons. We certainly need further studies on externally assessed personality measures, not on self-reported questionnaires, but a confirmation of this result would suggest that Dunkel is right to suggest that they point to the possibility of unification across individual differences in cognitive ability and personality under the banner of life history theory.
Curtis S. Dunkel (2013) The general factor of personality and general intelligence: Evidence for substantial association. Intelligence, In Press.
J. Philippe Rushton and Paul Irwing (2011) The General Factor of Personality: Normal and Abnormal in (Eds) Tomas Chamorro-Premuzic, Sophie von Stumm and Adrian Furnham. Wiley-Blackwell Handbook of Individual Differences, First Edition. 2011 by Blackwell Publishing Ltd.