Auditory Preemption versus Multiple Resources: Who Wins in Interruption Management?

We examined the effects of modality (auditory versus visual) and spatial separation when a simulated vehicle control (tracking) task (the ongoing task: OT) was time shared with a digit entry task (the interrupting task: IT), contrasting the predictions of auditory preemption theory with that of multiple resource theory. Participants performed the tracking task with auditory display of the phone numbers, or with visual display at eccentricities ranging from 0 deg (overlay) to 45 deg. Auditory input improved IT performance relative to visual, but disrupted OT performance, thereby supporting the role of auditory preemption. This cost did not grow with longer messages. In contrast, at eccentricities above 15 deg, auditory superiority emerged for both tasks, highlighting the role of multiple resources, and separation produced greater costs to the OT than to the IT. Therefore, both discrete tasks, and auditory delivery have inherent preemptive effects on the continuous visual OT. The results are also interpreted in the context of the non-linear costs to dual task performance with increasing separation from the eye-field to the headfield, and the support for different visual hemi-fields for concurrent processing of verbal and ambient spatial information.