Processing irrelevant location information: Practice and transfer effects in choice-reaction tasks

Left or right keypresses to a relevant stimulus dimension are faster when t he stimulus location, although irrelevant, corresponds with that of the res ponse than when it does not. This phenomenon, called the Simon effect, pers isted across 1,800 trials of practice, although its magnitude was reduced. Practice with the relevant stimulus dimension presented at a centered locat ion had little influence on the magnitude of the Simon effect when irreleva nt location was varied subsequently, and practice with location irrelevant prior to performing with location relevant slowed responses. After practice responding to stimulus location with an incompatible spatial mapping, the Simon effect was reversed (i.e., responses were slower when stimulus locati on corresponded with response location) when location was made irrelevant. When the response keys were labeled according to the relevant stimulus dime nsion (the Hedge and Marsh [1975] task variation), this reversal from pract ice with a spatially incompatible mapping was found for both the congruent and the incongruent relevant stimulus-response mappings. Thus, task-defined associations between stimulus location and response location affect perfor mance when location is changed from relevant to irrelevant, apparently thro ugh producing automatic activation of the previously associated response.