Effects of hearing differences on encoding and comparison information-processing stages

Abstract

Reaction times to spoken digits presented in a speeded memory scanning procedure were measured for groups of listeners with normal hearing (N=24) and with congenital or early-onset sensorineural hearing losses (N=12). Separate groups of 12 normal-hearing listeners were tested under conditions of good stimulus quality (no distortion, high SNR) versus poor stimulus quality (low-pass filtered, low SNR). The speeded memory scanning procedure allows total reaction time to be decomposed into ‘‘encoding’’ and ‘‘comparison’’ components which correspond to separate stages in a model of human information processing. At issue here is whether long-term effects of hearing loss, such as possible deficits in phonological and/or lexical representation of spoken language, lead to unusual processing costs at either the encoding or comparison stage. Experimental results suggest that impaired listeners incur the same encoding costs as normal-hearing listeners presented with poor-quality stimuli. However, comparison costs for the impaired listeners are no higher than those for the normal-hearing listeners presented with good-quality stimuli, and are unexpectedly lower than those for the normal-hearing listeners presented with poor-quality stimuli. [Work supported by NIH-NIDCD.]