Behavioral and Brain Sciences

Open Peer Commentary
Fitch & Denenberg: Sexual differentiation of the brain

Effect sizes and meta-analysis indicate no sex dimorphism in the human or rodent corpus callosum

Douglas Wahlsten a1 and Katherine M. Bishop a1
a1 Department of Psychology, University of Alberta, Edmonton, Alberta T6G 2E9, Canada


Sex dimorphism occurs when group means differ by four or more standard deviations. However, the average size of the corpus callosum is greater in males by about one standard deviation in rats, 0.2 standard deviation in humans, and virtually zero in mice. Furthermore, variations in corpus callosum size are related to brain size and are not sex specific.