Objective: The aim of this study was to demonstrate the importance of effort in human factors. Background: Effort has made its appearance in several diverse formats and applications. Eight of these are integrated in the current writing related to learning, looking, task switching, visual search termination, information access, choosing decision strategies, and behaving safely. Method: This is based upon a literature review. Results: The common elements of these different effort applications are highlighted, particularly, their manifestations in either implicit or explicit expected value decisions. Conclusions: There is a need to show how the metrics of effort and workload assessment influence decisions in human factors, particularly, those related to safety.