Variability in human motor and sport performance

In typical human factors/ergonomics (HF/E) contexts, the human operator functions as the “redundant subsystem” in the person-machine interface. Most systems rely on an engineered operating system with the human operator in a monitoring role, ready to engage control of the system as appropriate. Engineered design seeks to reduce variability and maintain a high level of precision; such is the case for aircraft and ocean-going transportation. What is referred to as unanticipated variability (Vincente & Rasmussen, 1992) represents situations that are unfamiliar to the operator and not anticipated by design engineers who created the system. Turvey et al. (1978) refer to this as context-conditioned variability, whereby a different set of actions produce the same task goal.