Individual susceptibility varies widely

What it is

Susceptibility to sensory conflict varies enormously between users. The same exposure leaves one person unaffected and forces another to stop within minutes. Judging a design by average discomfort ratings therefore masks the minority whose protection matters most.

Why it happens

Differences track several factors: vestibular sensitivity, prior motion-sickness history, awareness of one's own discomfort signals, and current fatigue or sleep debt. These are not fixed; the same person tolerates differently at different times, so susceptibility is a distribution rather than a label. The engineering consequence is that a scheme meeting the mean still frustrates a subset in real use, and dropout and complaints concentrate in that group.

Studying it

Repeated-exposure designs characterize the distribution: expose the same users at different times, record within-person fluctuation and between-person spread in discomfort ratings, and identify traits of the susceptible group. Variables include exposure duration, motion intensity, user state, and prior experience. Outcomes include the shape of the ratings distribution and the dropout rate, the latter being more directly decision-relevant. Avoid reporting means alone.

Where it stops holding

If exposure intensity sits well below the provocation threshold, individual differences matter little because everyone stays below threshold. If the product allows exit at any time and intensity adjustment, losses for susceptible users fall sharply and the design focus shifts from lowering average discomfort to providing control. Where exposure must continue, as in occupational training, screening and gradual adaptation are required.

Applying it

• Report the distribution of discomfort ratings and the dropout rate rather than means alone.
• Let users adjust motion intensity and exit promptly, handing control to the susceptible group.
• For mandatory exposure, provide a gradual adaptation protocol and prior screening.
• Verification: measure the ratings distribution and dropout proportion in the target population and confirm losses for susceptible users are acceptable.

Related

• Within the group: D4.05.1 Mismatch between visual motion and vestibular input causes discomfort · D4.05.3 Discomfort accumulates and is delayed
• Adjacent: N3.05 User screening and adaptation for immersive experiences · D4.08.3 Redundancy gains need task-specific measurement
• Search terms: susceptibility · individual differences · dropout rate