Context effects for degraded speech: Effects of age, preceding or subsequent contextual cues, and signal-to-noise ratio.

Predictive sentence contexts can be used to support speech understanding when words are degraded or unclear. Older adults are thought to maintain the ability to benefit from context. Because context effects are usually measured on words at the end of a sentence, it is unknown if a word's location in a sentence interacts with a listener's age and the word's degradation level to influence the context effect. In this study, listeners (20-76 years) with normal hearing were presented spectrally degraded (8-channel vocoded) speech and performed a phoneme categorization task for words embedded in various levels of speech-shaped noise at the beginning or end of sentences with congruent, incongruent, or neutral contexts. Phoneme categorization accuracy and response times were measured. Results showed effects of target word location within the sentence, especially at more difficult signal-to-noise ratios (-5 and -10 dB). Although there was no significant effect of age on the magnitude of the context effect, there were significant interactions between age, signal-to-noise ratio, and sentence position on response times. These findings suggest that listeners' context benefit depends on a degraded word's position within the sentence and support the theory that all listeners, including older adults, can benefit from context cues.