Figure 1. The VSRT and the associated brain activity.

Participants judged whether shapes changed across the 3 frames according to the following alteration rules: clockwise revolution for the shape in left upper corner, size increase for the left-side shape, multiplication for the center shape and clockwise rotation for the surrounding center shape. (a) One relation condition. The ellipsoid should continue revolving clockwise along the corners of the frame. (b) Two relation condition. The polygon should revolve clockwise and the ellipsoid should continue increasing in size. (c) Three relation condition. Together with the revolving triangle and multiplying ellipsoids, the surrounding rectangle should continue a clockwise rotation around the center. (d–f) Activation t-maps for one, two and three relations, respectively (brighter colors represent larger t-values, FDR, P < 0.05). More consistent recruitment of left caudal PFC is evident when relational complexity increases.