A rotated-heads visual oddball task (Begleiter et al., 1984) was used. Each of the 240 stimuli comprising the task was presented on a computer screen for 98 ms, with the inter-trial interval, during which subjects fixated on a dot in the center of the screen, varying randomly between 1 and 2 seconds. Two-thirds of the trials consisted of a plain oval, to which no response was required. On the remaining third of the trials, participants saw a superior view of a stylized head, in which a nose and one ear were depicted on the oval. Subjects were required to respond to these “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).
