Passive perceptual learning versus active searching in a novel stimuli vigilance task.

A criticism of laboratory vigilance or sustained attention research is the employment of static monotonous tasks with repetitive targets as opposed to the use of dynamic tasks with novel target stimuli. Unfortunately dynamic tasks employing novel stimuli may result in the mixture of two cognitive processes: active sustained attention search and passive perceptual learning. Moreover, the relative engagement of these two processes may depend on individual differences. In the present study, we examined this by having participants perform a dynamic auditory vigilance task with rare novel targets. In addition, some participants performed this task while also performing a secondary motor tracking task, a dual-task scenario. In the dual-task scenario, participants who failed to accurately detect the first target stimuli showed improvements in their tracking performance with time-on-task, suggesting reserves of attention. This improvement in tracking performance was not evident for those who accurately detected the first target stimuli, as their attention was likely actively engaged (searching). In addition, participants in the dual-task scenario who accurately detected the first target stimuli reported high workload and increased post-task tense arousal, results characteristic of participants performing static vigilance tasks. These results indicate the possibility that in a dynamic vigilance task with novel target stimuli participants may diverge in how they approach the task. Some participants will actively monitor the display for targets (search), whereas others will passively learn the target stimuli. Thus, these tasks may pose significant challenges to researchers who wish to examine vigilance in isolation from perceptual learning.