Flanker and Simon effects interact at the response selection stage

The present study aimed at investigating the processing stage underlying stimulus–stimulus (S–S) congruency effects by examining the relation of a particular type of congruency effect (i.e., the flanker effect) with a stimulus–response (S–R) spatial correspondence effect (i.e., the Simon effect). Experiment 1 used a unilateral flanker task in which the flanker also acted as a Simon-like accessory stimulus. Results showed a significant S–S Congruency × S–R Correspondence interaction: An advantage for flanker–response spatially corresponding trials was observed in target–flanker congruent conditions, whereas, in incongruent conditions, there was a noncorresponding trials’ advantage. The analysis of the temporal trend of the correspondence effects ruled out a temporal-overlap account for the observed interaction. Moreover, results of Experiment 2, in which the flanker did not belong to the target set, demonstrated that this interaction cannot be attributed to perceptual grouping of the target–flanker pairs and referential coding of the target with respect to the flanker in the congruent and incongruent conditions, respectively. Taken together, these findings are consistent with a response selection account of congruency effects: Both the position and the task-related attribute of the flanker would activate the associated responses. In noncorresponding-congruent trials and corresponding-incongruent trials, this would cause a conflict at the response selection stage.

Impact of task demands on spatial stimulis-response compatibility

Summary. Two experiments explored the impact of task demands on spatial stimulus-response compatibility. Task demands were manipulated to either emphasize stationary or dynamic aspects (positions or movements) in both stimuli and responses. For matched task configurations where the same features are emphasized for stimuli and responses results indicate a strong impact of task requirements on the relative magnitude of position-based vs. direction-based compatibility effects. For unmatched tasks where different features are emphasized in stimuli and responses results suggest that information about movement direction is recoded into position information, specifying the direction of stimulus or response movements in terms of their respective endpoint positions. Further, in some task configurations, an unexpected inverted direction-based compatibility effect was observed which can be explained in terms of referential coding. Referential coding acts to specify the position of a fixed stimulus relative to a moving stimulus, presumably based on an attentional spotlight mechanism.