Over recent decades, psychologists have converged on a model of personality sometimes called the Big Five Factors Plus IQ. As Geoffrey Miller points out in Spent, this is not some revelation that a charismatic genius like Freud has brought down from the mountaintop. Instead, it`s an emergent consensus of a whole bunch of researchers.
Conscientiousness is becoming popular as the Big Five factor that`s most like IQ in that it`s broadly applicable. Just as all else being equal, in hiring for almost any job you`d rather have somebody with more rather than less IQ, you`d like to have somebody with more rather than less conscientiousness.
Bruce G. Charlton has an interesting essay on IQ and Conscientiousness that begins:
The psychological attributes of intelligence and personality are usually seen as being quite distinct in nature: higher intelligence being regarded a â€?giftâ€™ (bestowed mostly by heredity); while personality or â€?characterâ€™ is morally evaluated by others, on the assumption that it is mostly a consequence of choice? So a teacher is more likely to praise a child for their highly Conscientious personality (high â€?Câ€™) â€“ an ability to take the long view, work hard with self-discipline and persevere in the face of difficulty â€“ than for possessing high IQ. Even in science, where high intelligence is greatly valued, it is seen as being more virtuous to be a reliable and steady worker. Yet it is probable that both IQ and personality traits (such as high-C) are about-equally inherited â€?giftsâ€™ (heritability of both likely to be in excess of 0.5). Rankings of both IQ and C are generally stable throughout life (although absolute levels of both will typically increase throughout the lifespan, with IQ peaking in late-teens and C probably peaking in middle age). Furthermore, high IQ is not just an ability to be used only as required; higher IQ also carries various behavioural predispositions â€“ as reflected in the positive correlation with the personality trait of Openness to Experience; and characteristically â€?left-wingâ€™ or â€?enlightenedâ€™ socio-political values among high IQ individuals. However, IQ is â€?effortlessâ€™ while high-C emerges mainly in tough situations where exceptional effort is required. So we probably tend to regard personality in moral terms because this fits with a social system that provides incentives for virtuous behaviour (including Conscientiousness).
Yet, it would seem like Conscientiousness is historically alterable — e.g., the Victorian English seem a lot more conscientiousness than their Regency grandparents, while today`s English seem like bigger screw-offs than their grandparents.