Beyond sensory conflict: The role of beliefs and perception in motion sickness

Abstract

Illusory self-motion often provokes motion sickness, which is commonly explained in terms of an inter-sensory conflict that is not in accordance with previous experience. Here we address the influence of cognition in motion sickness and show that such a conflict is not provocative when the observer believes that the motion illusion is indeed actually occurring. Illusory self-motion and motion sickness were elicited in healthy human participants who were seated on a stationary rotary chair inside a rotating optokinetic drum. Participants knew that both chair and drum could rotate but were unaware of the actual motion stimulus. Results showed that motion sickness was correlated with the discrepancy between participants' perceived self-motion and participants' beliefs about the actual motion. Together with the general motion sickness susceptibility, this discrepancy accounted for 51% of the variance in motion sickness intensity. This finding sheds a new light on the causes of visually induced motion sickness and suggests that it is not governed by an inter-sensory conflict per se, but by beliefs concerning the actual self-motion. This cognitive influence provides a promising tool for the development of new countermeasures.

Fig 1. Experimental set up with motorized chair and drum that could rotate independently from each other.

During the test the surrounding drum was closed and rotating around the stationary chair.

Fig 2. Scatterplots of A) chair rotation likelihood against drum rotation likelihood (n = 19); B) chair rotation likelihood against and Fullvection (i.e., percentage of time spent in full vection, n = 19).

Fig 3. Scatterplots of conflict_PB (A) and MSSQ (B) vs. motion sickness intensity (SSQ-TS, n = 19).

Diamonds and circles indicate the sick and non-sick group resp., according to self-judgement.