The training session consisted of 45 items which in a stepwise presentation showed the solution principles (see lower part of Fig. 1). The test also consisted of 45 items (see upper part of Fig. 1). Respondents had to judge which of the four figures on the right corresponded to the figure in the left frame. All items were presented on a computer screen positioned about 100 cm in front of the respondent. The tasks were presented at fixed 11 s interstimulus intervals. They were exposed for 7 s following a 2 s interval, when a cross was presented. During this time the students were instructed to press a button (1–4) which indicated their answer. All pictures were generated by the STIM stimulator.