Stimulus Discr1minability and S-r Compatibility: Evidence for Independent Effects in Choice Reaction Time

In contrast to flexible capacity theories of information-processing behavior, discrete stage models generally assume that the functioning of one stage (e.g., stimulus discrimination) proceeds independently of the demands on some other stage (e.g., response selection). These alternatives were tested by factorially varying stimulus similarity and stimulus-response compatibility in a speeded brightness discrimination task. The independent stage hypothesis was supported by the finding that, in general, the experimental variables did not have interactive effects on the means and higher order cumulants of the reaction time distributions. Some evidence, however, was found for weak interactive effects in the first of two sessions.