Uncertainty and processing routes in the selection of a response: an S-R compatibility study.

Stimulus-response (S-R) pairs are usually processed faster when-they are presented in a series that consists entirely of compatible relations rather than incompatible relations. A mixture of the two pairs in a series, which induces uncertainty, increases processing speed for both pairs, but more so for compatible S-R pairs. The results of three choice reaction time (RT) tasks showed that presentation of a precue that only indicated either compatible or incompatible S-R pairs reduced the detrimental effect of mixing pairs more for the former than for the latter pairs. A similar asymmetric reduction was observed in the third experiment when either pair was preceded by the same pair or the same class of pairing. Analyses of RT bins revealed that decreases in RT for the mixed compatible S-R pairs occurred only for the faster responses. It was shown further that errors consisted primarily of a correct application of an incorrect S-R transformation rule. The results are interpreted within the framework of the dimensional overlap model of Kornblum et al. (1990) suggesting two sources of the S-R compatibility effect; interference of primed responses and the need to suppress response priming.