Cortical sulci asymmetries in chimpanzees and macaques: A new look at an old idea

► We process a sample of 127 chimpanzee and 49 macaque magnetic resonance images. ► Using a novel software program, we quantified asymmetries in cortical sulci. ► Chimpanzees reveal population-level asymmetries, while macaques in general do not. ► Macaques indicate more individual brain lateralization than chimpanzees.