Working-memory load decreases mappings effects in spatial-compatibility tasks

The paper investigates the role of working memory for the translation of spatial stimuli into spatial responses. Performance is typically superior with compatible mapping between stimulus and response locations than with incompatible mapping (spatial-mapping effect). According to popular dual-route models, the spatial-mapping effect may arise from differences in the effectiveness of S-R translation, and/or from the effects of automatic response activation. Working-memory load should not affect the automatic route, but delay S-R translation in the incompatible condition, increasing the mapping effect under load. These predictions were tested in two dual-task experiments. Participants performed a spatial-compatibility task with compatible or incompatible S-R mapping, while memorizing different amounts of spatial (Experiment 1) or verbal (Experiment 2) information. In both experiments, working-memory load decreased the mapping effect, but did not eliminate it. Results are at odds with the dual-route account. An alternative explanation based on the response-discrimination account (Ansorge and Wühr in J Exp Psychol Hum Percept Perform 30:365-377, 2004) is proposed.