Testing auditory skills in children CI users: is phonemic discrimination related to acoustic variables only?

Theory suggests that improvements in speech perception can be linked to optimization of Cochlear Implant (CI) sound processing. At the same time, outcomes should be evaluated taking into account cognitive variables such as working memory and attention span. In particular this last variable, although it does not play a direct role in the specific processes of audition and language, may still influence speech perception and language production in children and may also influence outcomes. All studies focusing on speech coding strategy effects in the paediatric population have underlined the difficulties in discriminating the effect of a particular strategy from progress naturally acquired through learning. Better chances could be offered by tests that evaluate speech skills which are the least possibly linked to the cognitive asset as well as to rehabilitation characteristics. Discrimination is — in all Erber’s categories — the one that is less influenced by cognitive abilities that are required to perform closed and open set recognition tasks, where discrimination is the first ability to be developed by the deaf child after cochlear implantation (Hillenbrand, 1983). The ability to discriminate phonemes is considered to be basically language independent and their perception is less dependent upon a learning process. Phoneme discrimination tests have been developed to test children with the intention of optimizing prostheses regulation processes (Govaerts et al., 2006). One of the disadvantages of a contrast-based discrimination test is the potential lack of behavioural response to small perceptive differences. Vowels are easier to discriminate than consonants such as /z/, /v/, and /s/ both in infants and older children. From personal experience, phoneme contrast-based tests are extremely useful in evaluating CI children (Mancini et al., 2009), although results should be interpreted only in a contest of well-matched age and attention span. With this assumption, phoneme discrimination can be used as an evaluation test for different speech coding strategies. Starting from this assumption, the authors correlated open-set phoneme discrimination outcomes with attention span in a group of children with cochlear implants.