To react or not to react? Intrinsic stochasticity of human control in virtual stick balancing

Abstract

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 favour of event-driven control hypothesis: human operators only start actively controlling the system when the discrepancy between the current and desired system states becomes large enough. The event-driven models based on the concept of threshold can explain many features of the experimentally observed dynamics. However, much still remains unclear about the dynamics of human-controlled systems, which likely indicates that humans use more intricate control mechanisms. This paper argues that control activation in humans may be not threshold-driven, but instead intrinsically stochastic, noise-driven. Specifically, we suggest that control activation stems from stochastic interplay between the operator's need to keep the controlled system near the goal state, on the one hand, and the tendency to postpone interrupting the system dynamics, on the other hand. We propose a model capturing this interplay and show that it matches the experimental data on human balancing of virtual overdamped stick. Our results illuminate that the noise-driven activation mechanism plays a crucial role at least in the considered task, and, hypothetically, in a broad range of human-controlled processes.

Non-equilibrium phase transition in the model of human virtual stick balancing

“…Here we confront the model to the results of two experiments on virtual stick balancing conducted previously [6,11]. In both experiments, the subjects (operators) observed a mechanical system on a computer screen, and had to balance the stick upwards by moving the cart via computer mouse.…”

“…In both experiments, the subjects (operators) observed a mechanical system on a computer screen, and had to balance the stick upwards by moving the cart via computer mouse. In experiment 1 ("no mouse" condition) the mouse cursor was not present on the screen, so the operators could only observe the angular deviation of the stick from the vertical position [6]. In experiment 2 ("mouse" condition), the reference point (mouse cursor) was displayed near the upper tip of the stick.…”

“…Models which incorporate threshold-driven control activation can usually explain much dynamics observed in experiments. However, recent investigations of virtual overdamped stick balancing have revealed that control activations at large deviations occurs much more frequently then predicted by threshold-driven mechanism [6]. Besides, some of the most peculiar phenomena observed in human control behavior still remain unexplained by the models based on threshold-driven control activaProceedings of the 48th ISCIE International Symposium on Stochastic Systems Theory and Its Applications Fukuoka, Nov. [4][5]2016 tion.…”

“…1: The task of overdamped inverted pendulum (stick) balancing. The stick angle θ and the cart velocity υ (controlled directly by human operator) fully describe dynamics of the task [6]. Figure file is available under CC-BY [7].…”

Cloud Type Interpretation of Statistical Properties of Human Response Delay in Pendulum Balancing

“…Recently, a novel concept of noise-driven control activation has been proposed as a more advanced alternative to the conventional threshold-driven activation [15]. It argues that the control activation in humans may be not threshold-driven, but instead intrinsically stochastic, noise-driven, and stems from stochastic interplay between operators need to keep the controlled system near the goal state, on the one hand, and the tendency to postpone interrupting the system dynamics, on the other hand.…”