Verbal and nonverbal intelligence changes in the teenage brain

Abstract

Intelligence Quotient (IQ) is a standardized measure of intellectual ability that taps a wide range of cognitive skills ¹ . Across life span, IQ is generally considered to be stable with scores at one time point used to predict educational achievement and employment prospects in later years ¹ . Neuro-imaging allows us to test whether unexpected longitudinal fluctuations in measured IQ are related to brain development. Here we show that verbal and nonverbal IQ can rise or fall in the teenage years, with these changes in performance validated by their close correlation with changes in local brain structure. A combination of structural and functional imaging showed that verbal IQ changed with grey matter in an area that was activated by speech, while nonverbal IQ changed with grey matter in an area that was activated by finger movements. By using longitudinal assessments of the same individuals, we eschewed the many sources of variation in brain structure that confound cross sectional studies. This allowed us to dissociate neural markers for verbal and nonverbal IQ and to show that these general abilities are closely linked to the sensorimotor skills involved in learning. More generally, our results emphasize the possibility that an individual’s intellectual capacity relative to their peers can weaken or strengthen in the teenage years. This would be encouraging to those whose intellectual potential may improve; and a warning that early achievers may not maintain their potential.