Previous studies have found that post-lingually deaf adults with cochlear implants (CIs) generally have good phonemic categorization abilities, but performance can be fragile. Few studies have examined phonemic categorization in pre-lingually deafened children with CIs. This study asks if children who use CIs perceive fine-grained acoustic differences within a category. Next, assuming differences are perceived, we ask if they do so in a manner similar to adults with CIs, and how these patterns change over the course of adolescent development.
This study employed an eye-tracking paradigm to examine perception of voicing and fricative place of articulation in children with CIs. In previous speech categorization experiments, adult CI users typically demonstrate shallower identification functions, which is interpreted as a useful method of adaptation to uncertainty.
Participants ranged in age from 11 to 18 and included 17 CI users and 31 age-matched normal hearing (NH) peers. Children heard a token from either a b/p or s/ʃ continua (eight steps) spanning two words (bear/pear, sip/ship), and selected the corresponding picture from a screen containing pictures of all four words. Eye movements were monitored while they performed this task to measure how strongly each word was considered over time.
Mouse-click results (phoneme identification) for voicing demonstrated evidence for shallower slopes in CI users for both voicing and fricative continua. With respect to fixations, the CI users showed a less gradient effect of rStep to the competitor. Additionally, the CI users demonstrated minimal activation of competitors. These results suggest that children with CIs may adapt a wait and see approach, suppressing competitor activation and waiting to begin lexical access until substantial information has been accumulated.