Can adults and children use phonotactic knowledge to identify spectrally-degraded speech?

Word recognition is facilitated by a listener's phonotactic knowledge-rules that govern how speech sounds combine to form words in language. Spectrally degrading speech disrupts the representations of speech sounds, however, making it more difficult to recognize words. Because phonotactic knowledge increases with language experience, individuals with more mature language may be better able to leverage phonotactic knowledge when attempting to recognize degraded speech. In this study, we tested the hypotheses that (1) adults are more sensitive to phonotactic information during word recognition than children; (2) children with larger vocabularies are more sensitive to phonotactic information; and (3) spectral degradation disrupts sensitivity to phonotactic cues during word recognition. To test these ideas, 36 adults and 36 school-aged children completed English Decision and Lexical Decision tasks. Both were presented with high-fidelity (unprocessed) and 16-channel noiseband vocoded (degraded) speech. Adults were more accurate and faster than children in the tasks. Performance declined in both groups when the speech stimuli were degraded. Among child participants, those with larger vocabularies were faster at making lexical decisions. The results provide insight into how adults and children leverage phonotactic information when processing speech and how those strategies are influenced when speech is degraded.