Reduced is not off; a fade can replace travel
Aliases: reduced is not off · fade replacing travel · non-travel transition
What it is
Turning off travel motion is not freezing the display. A cross-fade still marks old versus new, with almost no optic flow. Reduced removes large translations, scales and parallax — the motions that drive a self-motion illusion — not every frame change. A fade is a substitute, not “motion off, therefore a hard cut.”
Why it happens
Vestibular conflict is driven mainly by large-field optic flow: many pixels moving in a common direction, which the visual system explains as the self moving through the world while the inner ear reports stillness. A cross-fade changes local contrast, not common-direction flow, so the conditions for vection are not met. At the same time, a luminance ramp on the target still offers a weak transient, so change detection need not collapse back to a cut.
Reading reduced as duration: 0 deletes the transition entirely; change blindness and identity breaks return together. The substitute is a channel swap: travel → opacity or colour, scale → a crop switch, parallax → static layering. The spatial story gets weaker; “something happened” remains.
Studying it
Among people who have declared the preference (or a condition that simulates it), compare cut, fade and short travel. Dependent measures: discomfort, change detection, identity recognition. The prediction is that fade approaches a cut on discomfort and beats a cut on detection. Do not let people who never declared the preference vote a fade down as “not flashy enough.”
Where it stops holding
- A fade that is a full-screen high-contrast flash becomes a photosensitivity risk — a different safety ceiling, not a reduced-motion failure.
- A fade that is too short is indiscriminable from a cut; the substitute needs a duration that can be registered without again blocking action.
- A shared-element morph is travel plus scale; the reduced branch should not keep the morph at a shorter duration, it should become a cross-fade.
Applying it
- Give every translation / scale / parallax a twin fade or colour transition, switched by the OS preference.
- Do not implement reduced as global
animation: none. - Check: with the OS setting on, the main path still shows that the page and the state changed, without full-page travel. If it becomes a cut and people cannot name the change, the substitute is too thin; if travel remains, the substitute never engaged.