Modality and task switching interactions using bi-modal and bivalent stimuli.

Investigations of concurrent task and modality switching effects have to date been studied under conditions of uni-modal stimulus presentation. As such, it is difficult to directly compare resultant task and modality switching effects, as the stimuli afford both tasks on each trial, but only one modality. The current study investigated task and modality switching using bi-modal and bivalent stimulus presentation under various cue conditions: no cue, either task or modality (single cue) or task and modality (double cue), with participants responding to either the identity or the position of an audio-visual stimulus at each trial. In line with previous research, task and modality switching effects showed sub-additive patterns, with switching costs decreasing as pre-stimulus cue information increased. The current data also showed that modality switching costs were more malleable than task switching costs as the former were eliminated when full and single cue information was provided, as well as when participants responded to the more efficiently processed task (position relative to identity). Conversely, task switching costs were only eliminated in the full cue condition, but were present for both tasks and both modalities despite a similar asymmetry in efficiency (vision relative to audition). The data further show that the specific task-modality combination being responded to impacted on combined task- and modality switching effects, with those combinations leading to either the greatest or lowest costs contributing most heavily to sub-additivity.