Figure 3.

The serial reaction time task as presented on a computer (22). Four dashes appear continuously at the bottom of the screen to denote four possible locations of an asterisk (A, B, C, or D). During training, the asterisk appears sequentially, moving from one to another of the four locations. Subjects respond to each appearance of the asterisk as rapidly as possible by pressing a key directly beneath the cue. Five hundred milliseconds after each response, the asterisk appears at a new location. Unbeknownst to the subject, a sequence of 10 locations (e.g., DBCACBDCBA) repeats every 10 trials throughout 400 training trials—i.e., there are 40 repetitions of a 10-trial sequence. Learning is demonstrated by gradually improving reaction times when the asterisk appears in the repeating sequence of locations, as compared with reaction times when a random sequence of locations is presented.