Made by AI, Directed by David Stein

Search
Emerging Interfaces

People Move Differently in Passthrough, and a 110-Person Study Finally Measured How Much

A four-fold suppression of head rotation. Researchers call it Passthrough Rigidity, and it explains discomfort that better hardware hasn't fixed.

3 min read

Video passthrough has improved enormously. Resolution is up, latency is down, and the specific complaints people had five years ago have largely been engineered away. Broad adoption still hasn’t happened, and people still report that wearing a headset in passthrough is tiring in a way that’s hard to articulate.

A paper posted September 21, 2026 goes after that gap by measuring what the body does instead of asking people how they felt.

“Passthrough Rigidity: The Behavioral and Visuomotor Costs of Mediated Perception” — Markus D. Solbach, Mohit Goyal, Sakar Khattar, Jayant Varma, Bjorn Vlaskamp, John K. Tsotsos and Konstantine Tsotsos — is a within-subject study with N=110, which is a large sample for this kind of work.

The method

Participants did a block assembly task requiring complex hand-eye coordination, under two conditions: natural viewing and video passthrough. The researchers captured synchronised oculomotor, kinematic and physiological data throughout.

That synchronisation is the contribution. Plenty of studies measure one channel. Capturing where the eyes go, how the head and hands move, and what the body is doing, all on the same clock, is what lets you see a compensation strategy rather than just a symptom.

What they found

  • A four-fold suppression of rotational head velocity. People stop turning their heads. Not slightly — by a factor of four.
  • Pronounced decoupling of head-gaze coordination. The normal relationship where the head and eyes move together to acquire a target breaks down.
  • Longer fixation durations and restricted visual search patterns, as the information-gathering burden shifts onto the oculomotor system.
  • Reduced blink duration, plus increased reported ocular strain and cognitive load.
  • These kinematic shifts correlate directly with worse task performance.

The authors read the head stillness as motor caution — an adaptive strategy. You are seeing the world through a mediated, imperfect reconstruction, so you stop making the fast head movements that would stress it, and you compensate with your eyes.

The talk above is background rather than a presentation of this paper — a Stanford researcher on using the human visual system to inform AR/VR design, which is the tradition this work sits in.

Why this matters for people building things

Two practical consequences.

First, the remaining problem may not be a display problem. The study’s framing is that resolution and latency improved dramatically while discomfort persisted. If the mechanism is a behavioural adaptation — the user throttling their own movement because the mediated view isn’t trustworthy — then more pixels won’t remove it. Something about the fidelity of the reconstruction has to change such that people are willing to move normally again.

Second, it has direct design implications for mixed-reality work. If you are building an installation, a training piece or a performance that puts people in passthrough:

  • Don’t design for head movement. Anything that assumes people will look around freely — content placed behind them, wide spatial layouts, rapid target acquisition across a room — is fighting a four-fold reduction in the movement it depends on.
  • Budget for eye fatigue, not just neck fatigue. The compensation lands on the oculomotor system. Sessions that feel fine on paper may be more tiring than a comparable non-passthrough experience.
  • Expect worse manual task performance in passthrough than your rehearsals in natural viewing suggest, particularly for anything requiring hand-eye precision.

None of that is new advice exactly — experienced XR builders have intuitions along these lines. What’s new is a number attached to it, from 110 people, with the mechanism identified.

Related Reading