Figure 1.

The attention-switching paradigm used in this study required subjects to select one stimulus exemplar (left vs right) within one dimension (faces vs scenes) on every trial. A, Each trial consisted of two consecutive responses followed by feedback. Red boxes indicate a possible response sequence. B–D show two consecutive trials with responses defining the three different trial types. For clarification, the stimuli are displayed schematically (F1, face 1; S1, scene1; F2, face 2; S2, scene 2). B, In this example, the subject is attending to F1 on the first trial (attended stimuli are displayed in italic). On the next trial, no novel stimuli are introduced and the subject keeps attending to F1. The second trial is thus defined as a repeat trial. C, On a novel switch trial, novel stimuli of the unattended dimension, in this case scenes, are introduced (S3 and S4). The subject detects this change and switches attention to one of two novel stimuli (here S3). D, Alternatively the subject can fail to detect the novel stimuli and keep responding to the previously relevant stimulus exemplar, in this case F1. The subject will then receive negative feedback and the second trial is defined as a novel nonswitch trial.