In the learning task, subjects had to practice instructed stimulus–response (S–R) associations. (a) For instruction, subjects were presented with four symbols simultaneously for 10 s, indicating left/right-hand responses for each symbol. The dashed box was not presented in the learning task. (b) During the following practice phase, single symbols were presented sequentially and subjects had to respond to each symbol as instructed before. Equal/unequal signs were not presented in the learning task. This procedure was repeated 20 times featuring a novel stimulus set each time. As control task, a version of the 1-back task was implemented with stimulus material and temporal structure identical to the learning task. (a) Again, subjects saw four symbols on a screen, but without right/left-hand labelling. Instead, for the last second, a dashed box highlighted the reference symbol for the first trial of the following single-trial phase. (b) For the following sequence of trials subjects were asked to perform a 1-back task, that is, subjects had to decide if the current and preceding symbols were identical or not. Randomly chosen left/right to same/different mappings were indicated by respective signs presented below the stimulus symbols.