Childhood hearing impairment: auditory and linguistic interactions during multidimensional speech processing.

Children with mild-severe sensorineural hearing losses often use hearing aids and aural/oral language as their primary mode of communication, yet we know little about how speech is processed by these children. The purpose of this research was to investigate how the multidimensional information underlying accurate speech perception is processed by children with mild-severe hearing impairments. The processing of the auditory and linguistic dimensions of speech was assessed with a speeded selective-attention task (Garner, 1974a). Listeners were required to attend selectively to an auditory dimension (gender of the talker) and ignore a linguistic dimension (word) and vice versa. The hypothesis underlying the task is that performance for the target dimension will be unaffected by what is happening on the nontarget dimension if the dimensions are processed independently. On the other hand, if the dimensions are not processed independently, listeners will not be able to attend selectively and performance for the relevant dimension will be affected by what is happening on the irrelevant dimension (termed "Garner" interference). Both children with normal hearing (N = 90) and children with hearing impairment (N = 40) showed some degree of Garner interference, implying that the dimensions of speech are not processed independently by these children. However, relative to the children with normal hearing, the children with hearing impairment showed normal Garner interference when attending selectively to the word dimension (normally effective at ignoring talker-gender input) and reduced Garner interference when attending selectively to the talker-gender dimension (more effective at ignoring word input). This pattern of results implies that the auditory dimension has a normal strength-of-processing level that makes it normally distracting and that the linguistic dimension has an underdeveloped strength-of-processing level that makes it easier to ignore in children with hearing impairment.