To react or not to react? A double-well potential model of event-driven human control

Understanding how humans control unstable systems is central to many research problems, with applications ranging from quiet standing to aircraft landing. Increasingly much evidence appears in favor of event-driven control hypothesis: human operators are passive by default and only start actively controlling the system when the discrepancy between the current and desired system states becomes large. The present study proposes a cognitive model describing the transitions between the passive and the active phase of control behavior. The model is based on the concept of random walk in double-well potential widely employed in physics. Unlike the conventionally used model of fixed threshold, the proposed model is intrinsically stochastic and thus conforms to the physiological interpretation of the threshold as a probabilistic rather than deterministic notion. The model is studied numerically and is confronted to the experimental data on virtual stick balancing. The results confirm the validity of the model and suggest that the doublewell potential can be used in modeling human control behavior in a diverse range of applications.