Fig. 5.

Reaction times (A) and error rates (B) for contrast decrement detection in the control experiment, as a function of set size (number of precued elements), for the two different difficulty levels (n = 8). Whereas error rates are unaffected by task difficulty, reaction times strongly differ depending on the task. The search slopes (average RT increase for each set size increase) are 38 ms per item and 1 ms per item, respectively, for the difficult and easy versions of the task, suggesting that the task difficulty alters the underlying attentional requirements.