“Oh they’re so big-headed”, a phrase often used to describe someone who believes that they are very intelligent or very good at something. In other words, someone who is very arrogant which in turn means that being told you have a big head is not a positive thing. I have particularly strong feelings about the use of this phrase as I myself have a large head. I am often teased for being big-headed though I like to think this isn’t because of any arrogance on my part but more the physical stature of my skull. So is there any link between having a physically big head and the intended meaning of this phrase, that you’re intelligent or skillful and arrogant with it.
There are no studies (that I could find) which have directly found a positive correlation between IQ and head size. Some researchers have looked at the effect of the pre-natal physical environment on subsequent IQ scores and found a significant correlation between birth weight and later IQ (Breslau et al., 1996) with birth weight relating to head size. However, this correlation has been suggested to be concealing a much larger effect at extremely low birth weights where the low weight may be symptomatic of other developmental abnormalities (Rutter et al., 1970, Education, health and behaviour (Longman, London)). This suggests that the correlation between low birth weights (and small head sizes) and low IQs is not direct and that both are related to developmental abnormalities due to things like having a mother who smoked during her pregnancy (Broman et al., 1975, Preschool IQ Prenatal and Early Developmental Correlates. New York: Lawrence Erlbau).
Maybe it is not our head size but the size of our brain that determines our intelligence and a weak link between these two has emerged though is apparent much more strongly when compared with the rest of the animal kingdom. In comparison with other animals, the brain size of humans is three times what you would expect in the average animal with animals like dolphins and other primates, which we consider intelligent, having larger than average brains. So maybe brain size is related to our intelligence though our variability in brain size (compared to the rest of the animal kingdom) is not enough to account for the variation in intelligence seen in humans. Something worth noting is that I have been using IQ and intelligence interchangeably and there is still an ongoing debate (to which I couldn’t do justice here) as to whether IQ scores are representative of intelligence.
Head size may not be related to intelligence though one group of researchers found that people with a larger head circumference were less likely to show decline in their cognitive abilities as they aged. They found no association between head circumference at birth and peoples’ scores on the cognitive function tests. This led them to suggest that brain development whilst you’re young is crucial in determining to what extent your cognitive abilities decline in old age.
In conclusion, there is very little (to no) evidence to support the statement ‘they have a big-head’ when referring to someone who believes themselves to be intelligent or skillful. The physical size of your head (unfortunately for me) has no bearing on how intelligent you turn out to be though does seem to mean that you fare better in your twilight years compared to your small-headed peers!