Inverse hysteresis effects in a real and virtual environment.

In sequential, repetitive motor tasks such as opening a stack of drawers, we tend to reuse prior motor plans to reduce cognitive load. This persistence, termed motor hysteresis, has been demonstrated in discrete reaching movements but not in discrete full-body movements. If hysteresis reflects a general principle of cost reduction, it should also manifest in full-body movements. To test this, we asked participants to perform a discrete full-body posture selection task: passing through apertures of varying widths. Width was varied in ordered sequences to induce hysteresis and body rotation was measured. To test whether full-body tasks, which require considerable space, scientific equipment, and personnel, could be conducted more efficiently in a virtual reality (VR) setup, we faithfully reproduced the task in VR with a second group of participants. Results showed that participants walked straight through wider apertures but initiated body rotation below a critical width. The critical width shifted with order, suggesting an inverse hysteresis effect. This inverse hysteresis was confirmed in the second participant group in the virtual environment. However, VR participants rotated at wider apertures, indicating a more cautious behavior. Comparable behavioral patterns across environments support the feasibility of VR for full-body movement studies. Nevertheless, validating critical findings in a real environment seems advisable. The observed inverse hysteresis has only been described in perception research so far, where it indicates repetition suppression. Our findings suggest that repetition suppression may also apply to motor planning, especially when mechanical costs are high.