Sexual dimorphism in hemispheric processing of faces in humans: A meta-analysis of 817 cases

A well-established neuroimaging literature predicts a right-sided asymmetry in the activation of face-devoted areas such as the fusiform gyrus (FG) and its resulting M/N170 response during face processing. However, the face-related response sometimes appears to be bihemispheric. A few studies have argued that bilaterality depended on the sex composition of the sample. To shed light on this matter, two meta-analyses were conducted starting from a large initial database of 250 ERP (Event-related potentials)/MEG (Magnetoencephalography) peer-reviewed scientific articles. Paper coverage was from 1985 to 2020. Thirty-four articles met the inclusion criteria of a sufficiently large and balanced sample size with strictly right-handed and healthy participants aged 18-35 years and N170 measurements in response to neutral front view faces at left and right occipito/temporal sites. The data of 817 male (n = 414) and female (n = 403) healthy adults were subjected to repeated-measures analyses of variance. The results of statistical analyses from the data of 17 independent studies (from Asia, Europe and America) seem to robustly indicate the presence of a sex difference in the way the two cerebral hemispheres process facial information in humans, with a marked right-sided asymmetry of the bioelectrical activity in males and a bilateral or left-sided activity in females.