A rotated-heads visual oddball task (Begleiter et al., 1984) was used. Subjects viewed 240 stimuli consisting of either an oval (two-thirds of trials – “standards”) or a superior view of a stylized head (one-third of trials – “targets”), in which a nose and one ear were depicted on the oval. Subjects were required to respond to target trials by pressing a button on either the left or right armrest of their chair, corresponding to the side of the head on which the ear appeared. On half the target trials the nose pointed up (such that the left ear appeared on the left side of the screen; an easy discrimination), while on the other half of target trials the head was rotated 180° so that the nose pointed down (left ear appeared on the right side of the screen; a hard discrimination). Stimulus duration was 98 ms, and the inter-trial interval, during which subjects fixated on a dot in the center of the screen, varied randomly between 1 and 2 seconds.
