Assessing the cognitive demands of speech listening for people with hearing losses.

OBJECTIVE: Measures of listening effort can provide a useful complement to measures of listening performance. The purpose of the present study was to measure the effort required of hearing-impaired subjects when they listen to speech.
METHOD: Our subjects performed two tasks simultaneously: a speech task, which took the form of listening to connected discourse; and a digit-memorization task, which competed with the speech task for cognitive resources. Changes in speech-listening effort altered the distribution of resources between the two tasks and modulated memory performance. In two experiments, this dual-task test was given to individuals with congenital/early-onset hearing loss or with presbyacusic hearing loss. We first asked whether they could perform the dual tasks at reasonable levels. If they could, we then asked what their performance revealed about the effortfulness of speech listening, compared with the effort required of normally hearing control subjects.
RESULTS: We found the dual-task test to be broadly accessible to hearing-impaired persons. We also found evidence that speech listening was abnormally effortful for both hearing-impaired groups.
CONCLUSIONS: These findings encourage further study of attentional and other cognitive factors that accompany speech listening by the hearing impaired.