Categorical Perception.

Question

What was categorical perception? -Peter Eimas

Answer

Categorical perception is the observation that we hear speech sounds as members of a particular category, and we tend not to hear variations within that category. For example, the phoneme /b/ is a voiced consonant. It differs from /p/, which is unvoiced. In a syllable like /ba/, the vocal cords are engaged fairly quickly after air begins to flow past the lips. The amount of time from the start of air flow to the engagement of the vocal cords is called voice onset time. When the voice onset time is fast, the syllable will be heard as /ba/. Not all spoken /ba/ syllables will have a voice onset time that is exactly the same, but we do not notice those variations. We hear them all as /ba/.

At some point, the voice onset time gets long enough that we now hear the syllable as /pa/. When the syllable goes from /ba/ to /pa/, we do not hear anything in between /ba/ and /pa/. Rather each syllable we hear is classified as one or the other. That is why the perception is categorical. We always categorize the speech sound as belonging to one category or another of speech sounds.

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