Engaging the human operator: a review of the theoretical support for the vigilance decrement and a discussion of practical applications

Vigilance, or the ability to sustain attention for extended periods of time, has been of interest to the human factors and ergonomics community for 70 years. During this time, several theories have attempted to account for the performance effects commonly associated with vigilance (i.e. the decrement, which manifests in fewer correct detections and longer response times to targets over time). We provide a cohesive review of the current empirical support for the three major theories explaining the vigilance decrement and describe the limitations of each theory herein. The three overarching theories of vigilance performance and the vigilance decrement include: cognitive resource theory, mindlessness theory and mind-wandering theory. Importantly, each of these theories relies on unique definitions of task engagement to understand operator overload or underload. The differences in the operationalisation of task engagement are problematic in the application of vigilance research to the real world. In this article, we describe the utility of a unified definition of task engagement and demonstrate how resource theory is better poised to account for cognitive task engagement than physical task engagement, which is emphasised in other theories.