Disrupting monotony while increasing demand: benefits of rest and intervening tasks on vigilance.

In the experiments presented here, we examined the impact of intervening tasks on the vigilance decrement. In Experiment 1 participants either (a) continuously performed a visuospatial vigilance task, (b) received a rest break, or (c) temporarily performed a different, demanding visuospatial task in the middle of the vigil. Both taking a rest break and performing the intervening task were found to alleviate the vigilance decrement in response times. Target detection accuracy was equivalent across groups. In Experiment 2 we obtained subjective ratings of task demand, boredom, motivation, and mind wandering for both the vigilance task and intervening task administered in Experiment 1. The intervening task was rated as more demanding in terms of mental demand, physical demand, temporal demand, own performance, effort, and frustration. In addition, participants also reported being more bored, less motivated, and reported mind wandering more frequently when completing the vigil. Disruptions to task monotony (even if cognitively demanding), can alleviate the vigilance decrement. The implications of this finding with respect to current theoretical accounts of the vigilance decrement are discussed.