Influence of cross-modal load on cognitive processing and decision-making

Thoughtful design of multitask scenarios alleviates some competition for limited attentional resources. However, tasks that demand separate perceptual resources may still result in processing overload. In this experiment, participants completed a visual search task and auditory N-back task (absent, 1, 2, 3) in isolation or together via a within-subjects, randomized, and factorial paradigm. We assessed cross-modal influence using summary statistics, a nonparametric metric of efficiency, and complementary evidence accumulation models. As predicted, we found dual-task deficits in both tasks when paired, and further declines in performance with increased task load. Further, our modeling results indicated a reconfiguration in decision-making architecture as cross-modal load increased—lower response caution in one task (thresholds) to compensate for the unavoidable degradation of processing quality in another (drift rates). Overall, our results suggest that dual-task capacity limits not only govern the amount of information humans can process, but impose (in)stable decision-making strategies across competing resources streams.