Schematic paradigm and pupil-size traces for Exp. 1 (a) and Exp. 2 (b).

Pupil size was larger on attend-dark than on attend-bright trials, which reflects attentional modulation of the PLR. This modulation was evident from 717 ms (in Exp 1) and 656 ms (in Exp. 2) after the presentation of the cue, as indicated by the gray shading. In Exp. 1 there was also an overall constriction in response to the (visual) cue, with a mean latency of 241 ms.