Choice Reaction Time As a Function of Stimulus Uncertainty, Response Uncertainty, and Behavioral Hypotheses

2 studies were concerned with the effects of stimulus and response uncertainty upon reaction time (RT). In Experiment I, it was found that changes in stimulus uncertainty produced linear changes in RT but changes in response uncertainty produced a step function with a maximum at 1 bit of response uncertainty. Correct pretrial guesses as to which stimulus event would occur tended to facilitate RT only in the more complex response-uncertainty conditions. Experiment II replicated the finding that stimulus uncertainty per se is a variable effecting RT. The results were discussed relative to the role of attention and response conflict. (PsycINFO Database Record (c) 2006 APA, all rights reserved).