Do individual differences interact with lexical cues during speech recognition in adverse listening conditions?
Thesis DisciplineSpeech and Language Sciences
Degree GrantorUniversity of Canterbury
Degree NameMaster of Audiology
Purpose: This thesis examines the effect of listener characteristics (i.e., cognition and vocabulary) and language-based factors (i.e., lexical frequency and phonological similarity) on speech recognition accuracy in adverse listening conditions. Method: Fifty listeners (40 females and 10 males) aged 18-33 years and with normal hearing (puretone thresholds ≤ 20 dB HL, 0.25-8 kHz) participated. They completed a speech perception experiment, which required listeners to repeat back non-sensical English phrases presented at a variety of signal-to-noise ratios (-5, -2, +1, and +4 dB SNRs). In addition, all listeners undertook assessments of vocabulary knowledge (PPVT-IV) and cognition (WAIS -IV). The primary dependent variable was individual content word recognition accuracy, and results were analysed using binomial mixed effects modelling. Results: Listeners demonstrated variability in their speech recognition abilities, and their vocabulary and cognitive scores. Statistical analysis revealed that listener-based factors affected word recognition. Listeners with faster processing speed and larger working memories exhibited higher word recognition accuracy. Surprisingly, listeners with higher non-verbal intelligence scores exhibited lower word recognition accuracy. Vocabulary knowledge interacted with SNR, such that as the listening conditions became more favourable, listeners with larger receptive vocabularies identified more words correctly. Similarly, main effects were also present for language-based factors. The more phonologically distinct a word was, the more likely it was to be correctly identified; higher frequency words were more likely to be accurately recognised. In addition, higher frequency words were identified more accurately at higher SNR levels. Finally, listener- and language-based factors interacted. The positive effect of working memory on word recognition was reversed as word frequency increased; on the other hand non-verbal intelligence’s negative influence on word recognition was reversed as word frequency increased. Conclusion: In the current cohort, listener and language-based factors interacted in the process of word recognition in noise. These results provide an insight into the underlying speech recognition mechanisms in adverse conditions. Further understanding of how these listener differences affect an individual’s speech processing may lead to the development of improved signal processing techniques and rehabilitation strategies.