Simple auditory and visual interruptions of a continuous visual tracking task: modality effects and time course of interference.

Research has produced conflicting evidence regarding whether performance of an on-going visual task is disrupted more by an interruption from a visual or an auditory alert. Tasks and alerts studied to date have been complex or idiosyncratic. This experiment examined how the modality of simple alerts-visual icons or auditory tones-affected performance of an on-going visual task. Participants (58 females and 4 males) tracked a visual target while performing a choice reaction time task in response to alerts. Visual alerts were more harmful to performance of the tracking task. Dual task workload was lowest with an auditory alert, provided there was not noise present. Interruptions affected tracking task performance for around 1500 ms. Results supported the predictions of Multiple Resources Theory and showed no evidence of auditory preemption. In practical applications for which an on-going visual task is interrupted, auditory alerts may be less disruptive and may reduce perceived workload. Practitioner Summary: Many practical scenarios involve on-going visual tasks that are interrupted by simple alerts requiring a simple response. Auditory alerts may be less disruptive than visual alerts and may reduce perceived workload. A conservative estimate is that the effects of even simple interruptions will last a minimum of 1500 ms. Abbreviations: ANOVA: analysis of variance; LSD: least significant difference; TLX: task load index.