These findings highlight one of the most important principles emerging from neuroimaging research, which is that differences in brain size cannot be straightforwardly interpreted as imparting any sort of functional advantage or disadvantage. Male/female differences and the striking variability of brain volumes in the presence of equal intellectual capacity demonstrate the lack of a linear relationship, while the inverted U shape of brain trajectories indicates the dissociation between ongoing maturational improvement in cognitive ability while brain volumes have already begun to fall during mid-late adolescence. Features such as neuronal connectivity and receptor density may confer functional differences that are not captured with gross structural measures.
