Fig. 2 Individual and group differences in grey matter, in (a) the amygdala and (b) the OFC, from voxel‐based morphometry of brain images. The coordinates (x, y, z) at the voxel of maximal effect are shown on the vertical axis. Mean values (±2 standard errors) are given, relative to the grand mean, for 17 46,XX females designated by C. Eleven 45,X^m females (maternal X‐chromosome only) are designated by M and 10 45,X^p females (paternal X‐chromosome only) are designated by P. At positions 1–13, data for 13 individual Xp deletion subjects (46,XXp–) are given in order of increasing size of deletion from the telomere, from left to right. (There are two individuals at position 3/4 with identical deletions: a mother and daughter.) There are substantial grey matter differences between subjects 8 and 9 in both the amygdala and the OFC. The units of our response variable are adimensional probabilities pertaining to the proportion of brain tissue in the region that is grey matter. The magnitude of contrast between individual values or group means can easily be calculated. For example, in the amygdala at coordinates –37.5, –12. –24, the difference between normal subjects (–0.05) and Turner syndrome patients (0.02) is ∼0.07, corresponding to a 7% difference in grey matter volume.