Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Speech and Hearing Science



Research Advisor

Mark S. Hedrick, PhD


Kathleen Faulkner, PhD Jillian H. McCarthy, PhD Kevin Reilly, PhD Susie Robertson, PhD Krystal Werfel, PhD


audio-visual, cochlear implants, vocabulary, word learning


Objective. It is well established that being able to see someone’s mouth move as they speak boosts speech perception for children with cochlear implants (CIs). Thus, children with CIs are often instructed to orient themselves toward the person they are listening to, to gain access to visual speech cues. Children with CIs who are better “audiovisual integrators,” or those who experience an auditory-visual (AV) enhancement effect (higher performance for AV information than auditory-alone (AO) or visual-alone (VO)), are more likely to have better speech and language outcomes after receiving their CI than children with poorer AV integration skills. While AV integration of speech appears to be intimately tied with speech perception as well as speech and language development, its role in vocabulary acquisition is not well understood. This study examined novel word learning across two tasks, AV and AO, and sought to answer the following questions: (1) How does access to AV information impact novel word learning success for children with CIs and children with normal hearing (NH) listening to normal and CI-simulated speech? (2) How do individual patterns of visual attention during learning relate to individual word learning outcomes? (3) What measured factors (hearing history, device characteristics, maternal education level, etc.) contribute to novel word learning across AV and AO tasks? Methods. Twelve children with CIs (M = 7 years; 9 months) and twenty-four age- and sex-matched children with NH (M = 7 years; 8.6 months) completed two novel word learning tasks, AV and AO. Across both tasks, a female speaker was positioned on the top half of the screen and narrated a story. The corresponding story page and object to-be-learned was displayed on the bottom half of the screen. During the AO task, a black box was positioned over the speaker’s face to block access to visual speech cues. Twelve object-label pairs were presented across three blocks and word learning was assessed with a four-alternative forced-choice (4AFC) task following each block of presentations.

Results. Across listener groups, children did not learn significantly more words in the AV task as compared to the AO task. Within the group of children with CIs, two subgroups of performers were noted, “higher” and “poorer” word learners. Individual visual attention patterns corresponded with individual word learning outcomes for children who use CIs in these two performance groups. Children with CIs who spent more time looking at the speaker’s mouth learned more words than children who spent less time attending to the speaker’s mouth. Additionally, earlier age of amplification was significantly correlated with better learning outcomes. Many subscales across the LEAF, a parental report of executive functioning skills, were significantly correlated with word learning in the AO and AV tasks. Outcomes on the TONI-4, a nonverbal intelligence measure, and the Blending subtest of the CTOPP-2, an assessment of phonological processing, were also correlated with learning outcomes.

Conclusions. This study found no significant main effect of task type, which suggests that encouraging children with CIs to orient themselves to the speaker they are attending to may not be sufficient to support or improve vocabulary acquisition, particularly for children who demonstrate difficulty acquiring new words. Age of amplification, age of implantation, and phonological processing skills differentiated the two performance groups. Group differences also emerged where poorer and better CI performers showed differences in their visual attention to the task. These outcomes indicate that early learning and development of strategies for word learning warrants further investigation.

Declaration of Authorship

Declaration of Authorship is included in the supplemental files.




2020-32-Thornton-DOA.pdf (297 kB)
Declaration of Authorship