Word-Frequency Effect and Errors in the Perception of Speech

Abstract

The following interpretation of the word frequency effect—the tendency for common words to be perceived correctly at much lower speech to-noise ratios than uncommon words—was proposed and verified experimentally. When a stimulus word is only a few decibels below its intelligibility threshold, many of its features—the number of syllables, for example—are still perceived correctly. If enough such features are heard, then only a small number of English words will be consistent with them. Subjects' incorrect responses will be taken from that small set of words, and furthermore they will usually be the relatively common words in the set. If the stimulus is an uncommon word and there are common English words that are phonetically quite similar to it, then these common words will usually be given as (incorrect) responses except at quite high speech-to noise ratios. This interpretation is confirmed by an analysis of errors in an articulation test. The results show that all subjects tend to give the same incorrect responses, that these incorrect responses are usually more common than the stimuli to which they were given, and that, when a word is not confused with another in this way, its threshold is relatively low regardless of its frequency of occurrence in English usage.