Evidence against stimulus-effect priming as the source of modality pairing effects in task-switching

Abstract Task-switch costs are affected by the pairings of stimulus and response modalities. For example, switch costs are reduced when switching between visual-manual and auditory-vocal tasks compared to switching between visual-vocal and auditory-manual tasks. These modality pairing effects are generally interpreted as reflecting increased crosstalk between the stimuli and response-related action effects for the two tasks. However, the exact mechanism by which this crosstalk operates—stimulus-effect priming or conflict between central operations—is unclear. In four experiments, we manipulated the modality compatibility between stimuli and experimentally-induced action effects, such that tasks overlapped in the stimulus modalities, effect modalities, both, or neither. Experiment 1 conceptually replicated prior reports of modality pairing effects in task-switching in which switch costs were reduced when similar stimulus and effect modalities were encapsulated within tasks. In Experiments 2a, 2b, and 3, symmetrical switch costs across tasks provided evidence against the stimulus-effect priming account, instead suggesting that modality pairing effects stem from interference between the representations engaged by central operations. These results help to characterize the mechanism underlying modality pairing effects in task-switching and add to a growing body of work illustrating how relationships between stimuli and response-related action effects influence response selection processes.