Constraints in task-set control: modality dominance patterns among effector systems

Flexibility in configuring task sets allows people to adequately respond to environmental stimuli in different contexts, such as in dual-task situations. In the present study, we examined to what extent response control is influenced by the modality of a concurrently executed response. In Experiment 1, participants responded to auditory stimuli with either vocal responses and/or saccades. In Experiment 2, vocal responses were combined with manual responses. In both experiments, we found asymmetric dual-response costs, that is, the response time difference between single- and dual-response conditions varied between response modalities. It is important to note that the same (vocal) response showed substantial dual-response costs when combined with saccades (Experiment 1) but no such costs when combined with manual responses (Experiment 2). Experiment 3, combining saccades with manual responses, revealed stronger dual-response costs for manual responses than for saccades. Together, these findings suggest an ordinal dominance pattern among response modalities, representing flexible, response-based resource scheduling during task-set configuration.