Impact of cognitive load and sentence predictability on cognitive spare capacity in elderly adults with hearing loss

Abstract

Listening effort is needed to understand speech that is degraded by hearing loss and/or a noisy environment, and this in turn reduces cognitive spare capacity (CSC), the amount of cognitive resources available for allocation to concurrent tasks. Sentence context is known to boost speech perception accuracy, but how does context affect CSC? Here, we examine the impacts of context and cognitive (memory) load on behavioral measures of CSC. Elderly, hearing-impaired adults listened to noise-masked, spoken sentences in which sentence-final words were either predictable or unpredictable. Each trial began with visual presentation of a short (low load) or long (high load) sequence of to-be-remembered digits. Accuracy and response times for word recognition and digit recall were both facilitated by sentence predictability, indicating that CSC was greater when sentences were predictable. In addition, response times for both words and digits and accuracy for digits were impaired in the high load condition, reflecting decreased CSC under cognitive load. Participants’ baseline cognitive capacity (from a pre-test of working memory) generally did not moderate these effects. Results support the idea that predictable sentence contexts can support CSC and thereby improve ease of listening in elderly adults with hearing loss.