Searching working memory for the source of dual-task costs.

Dual-task costs depend on the specific pairings of stimulus and response modalities. Such findings are analogous to domain-specific effects in the working memory (WM) literature, in which items compete for limited capacity when they involve related types of information. The present study explicitly examines the relationship between modality-pairing effects on dual-task costs and domain-specificity effects on WM capacity. Participants maintained a sequence of either locations or tones in WM, and then performed a choice reaction time task in which they responded either vocally or manually. The stimuli for the choice reaction time task were held constant, but its response modality affected the interference observed in WM: vocal responses interfered with WM for tones and manual responses interfered with WM for locations. These findings indicate that response selection engages domain-specific WM processes and that interference within these processes may account for modality-pairing effects.