Extraction of indexical and linguistic information as a function of duration in the older population

When someone speaks information is present in a number of forms. The most obvious information is what the person has said (linguistic message). However, indexical information relating to the physical characteristics of the speaker is also embedded in the speech sound wave and influence judgements about the speaker such as whether they are a man or woman. Previous research studied how vowel recognition and speaker-sex discrimination information accumulates as a function of speech duration in the normal-hearing young population [D. R. R. Smith, Acta Psychol. 148, 81–90 (2014)]. We extended this research by investigating the build-up of linguistic and indexical information in the older population ( M age 72-years). Psychometric functions were collected plotting percent correct speaker sex discrimination and vowel recognition, as a function of vowel duration (5–40 ms), for older listeners compared to younger listeners ( M age 22-years). Older listeners’ performance on both tasks was markedly impaired compared to younger listeners’ performance. It is argued that deficits in the accumulation of indexical information at short durations might partially underlie the problems the older population experience in understanding speech and following conversations, especially where who is speaking is constantly changing such as in a noisy restaurant where several people are conducting a conversation.