Unity Assumption

A concept from multisensory-perception research (Welch and Warren, 1980; Welch, 1999) describing the observer's implicit judgement that signals arriving through different senses originate from the same underlying event or object. When the unity assumption holds, the brain fuses the signals into a coherent multisensory percept; when it breaks down, the signals are processed as independent streams, increasing cognitive load. In accessibility design, respecting the unity assumption means ensuring that audio, tactile, and haptic cues representing the same concept are temporally synchronised and semantically aligned so the user experiences a single object rather than several competing outputs.