Fig. 1.

Task description. (A) Trial sequence. Observers were asked to classify a target array based on either the average color (red vs. blue) or shape (square vs. circle). Only one dimension was relevant for the duration of the session. Preceding the target array was an irrelevant prime array, which could appear with a PTI of 100, 200, or 500 ms. Auditory feedback was given immediately following the response. (B) Examples of prime (P) and target (T) arrays with high and low variance on the color dimensions. Response time facilitation was observed when the variance matched (Upper Left, Lower Right).