Fig. 2. Response surface analysis (RSA) of the interactive association of positive schizotypy and AQ imagination with left and right head hippocampal volumes (mm³).

The blue line is the balance axis, and the black dotted line is the bias axis, where the balance axis represents equal expressions of autistic and positive schizotypy traits, and the bias axis (orthogonal to the balance axis) represents the relative and progressive dominance of autistic and/or positive schizotypy traits. Figures show a curvilinear relationship between these traits and hippocampal volumes, with volumes being smaller, although nonsignificant (p > 0.05), along the bias axis and particularly in individuals with a positive schizotypy-dominant trait profile, and larger in individuals with relatively balanced levels of positive schizotypy and AQ imagination, and particularly in individuals with either low-low or high-high trait profiles (Left: β(se) = 34.93 (14.36), 95%CI = (6.79, 63.08), p = .015; Right: β(se) = 52.46 (15.46), 95%CI = (22.16, 82.75), p < .001). Surface colour-coding represents the volume of the hippocampus from low (green) to high (red).