The influence of individual and linguistic factors and the segmentation strategies of older listeners in adverse conditions

Purpose: Firstly, this study aimed to examine the influence of listener-based behavioural characteristics and the statistical properties of language on older listeners’ speech perception in adverse conditions. Next, it aimed to determine the extent to which older listeners relied on syllabic stress cues to segment the speech stream in these conditions. Method: One hundred and three older healthy listeners repeated six syllable phrases presented at four signal-to-noise ratios (SNRs) – -5, -2, 1, and 4 dB. The phrases were orthographically transcribed and scored for recognition accuracy using a binary correct/incorrect coding at word level. Behavioural tests examining participants’ hearing acuity, vocabulary knowledge, working memory, non-verbal intelligence and processing speed were also conducted. Each phrase was further coded based on the lexical boundary error (LBE) patterns evidenced within the orthographically transcribed phrases—as an indicator of the participants’ lexical segmentation strategies. Results: As listening conditions deteriorated, older listeners’ speech recognition accuracy decreased. Those who exhibited higher hearing thresholds and poorer working memory scores also exhibited reduced speech perception accuracy (when analyses controlled for vocabulary knowledge, non-verbal intelligence and processing speed). The statistical properties of language had the largest effect on word recognition scores. Words with higher lexical frequencies and larger phonological neighbourhoods were associated with greater word recognition accuracy. Older listeners exhibited more predicted errors than unpredicted errors in their speech segmentation patterns—demonstrating a reliance on syllabic cues to segment the speech stream in adverse conditions. Degree of hearing loss (i.e., normal hearing, slight, and mild to moderate) did not appear to effect segmentation strategies. Conclusions: While older listeners’ speech perception accuracy is influenced by working memory and audibility, implicit linguistic knowledge also plays a considerable role in the ability to comprehend speech in adverse conditions. The degree of hearing loss, at least that measured by the current study, did not appear to influence segmentation strategies to a notable degree