Preparation for Donders' type B and C reaction tasks

Several variants of a precued reaction time experiment were performed to assess preparation for Choice (Donders' type B) or Go/No-Go (type C) reaction tasks. On each trial, the imperative stimulus could necessitate either a keypress with the left forefinger, the right forefinger, or no response. A precue given at lead times of 50-750 ms either informed the subject whether the task was a type B task (left or right forefinger response), a type C task (e.g., left forefinger or No Go), or carried no information (all three possibilities remained open). The noninformative cue produced minor facilitation of reaction time at long lead times only. At lead times of 50-250 ms, the other two precues speeded reactions by about 50 ms. At precue intervals of 400-750 ms, Go/No-Go reactions averaged 25 ms faster than Choice reactions in an experiment which utilized appropriate controls for stimulus and task parameters. The mixed-trial design rules out gross motor (e.g., postural) adjustments as an explanation for the advantage of C over B reactions. An interpretation in terms of a two-stage theory of motor preparation is discussed.