Context effects on lexical tone categorization in quiet and noisy conditions by young, middle-aged, and older individuals

Previous studies focused on how contexts affect the recognition of lexical tones, primarily among healthy young adults in a quiet environment. However, little is known about how senescence and cognitive decline influence lexical tone normalization in adverse listening conditions. This study aims to explore how F0 shifts of the preceding context affect lexical tone identification across different age groups in quiet and noisy conditions. Twenty-two Mandarin-speaking young adults, 22 middle-aged adults, and 21 older adults with mild cognitive impairment (MCI) participated in tone identification tasks with and without speech contexts. The identification tasks with contexts were conducted in quiet and babble noise with signal-to-noise ratios (SNRs) set at 5 and 0 dB. Results showed that contextual F0 cues exerted an equal impact on lexical tone normalization across all three age groups in the quiet environment. Nevertheless, under SNRs of 5 and 0 dB, noise nullified such an effect. Moreover, working memory was negatively correlated with the size of lexical tone normalization in the older group. These findings suggest that context effects on Mandarin tone normalization tend to be resistant to senescence and MCI but susceptible to babble noise, offering further insights into the cognitive processing mechanisms underlying speech normalization.