Same People, But Not the Same Brain These brain scans are part of a longitudinal study that repeatedly compares the proportion of grey matter from childhood through adolescence. Grey matter is reduced as white matter increases, in part because pruning during the teen years (the last two pairs of images here) allows intellectual connections to build. As the authors of one study that included this chart explain, teenagers may “look like an adult, but cognitively they are not there yet” (K. Powell, 2006, p. 865).

NITIN GOGTAY ET AL./NATIONAL ACADEMY OF SCIENCES, USA