Phoneme Restoration Effect

The phoneme restoration effect is a perceptual illusion in which listeners hear a spoken word as complete and intact even when one of its speech sounds has actually been removed from the recording and replaced with an extraneous noise, such as a brief cough or tone, with most listeners unable to identify which part of the word was covered by the noise or even to notice consciously that anything was missing at all. The psychologist Richard Warren demonstrated the effect in an influential 1970 study using the word legislature, in which a segment of the recording was excised and replaced with a cough-like sound; listeners overwhelmingly reported hearing the word normally, with the cough perceived as occurring somewhere else in the sentence rather than as replacing missing speech. The effect is understood to reflect the strong influence that surrounding linguistic and contextual information, including the rest of the sentence and the listener's knowledge of the language, has on filling in gaps in the raw incoming acoustic signal, so that speech perception is not a simple bottom-up registration of sound but an active reconstruction shaped heavily by expectation. The phenomenon is frequently cited in the study of top-down processing in perception, alongside related visual completion effects, as evidence that the perceptual system routinely supplies missing information rather than passively reporting only what physically reaches the sense organs.