Individual differences in CI users’ lexical access (Nagels et al., 2019)

Purpose: The current study investigates how individual differences in cochlear implant (CI) users’ sensitivity to word–nonword differences, reflecting lexical uncertainty, relate to their reliance on sentential context for lexical access in processing continuous speech.

Method: Fifteen CI users and 14 normal-hearing (NH) controls participated in an auditory lexical decision task (Experiment 1) and a visual-world paradigm task (Experiment 2). Experiment 1 tested participants’ reliance on lexical statistics, and Experiment 2 studied how sentential context affects the time course and patterns of lexical competition leading to lexical access.

Results: In Experiment 1, CI users had lower accuracy scores and longer reaction times than NH listeners, particularly for nonwords. In Experiment 2, CI users’ lexical competition patterns were, on average, similar to those of NH listeners, but the patterns of individual CI users varied greatly. Individual CI users’ word–nonword sensitivity (Experiment 1) explained differences in the reliance on sentential context to resolve lexical competition, whereas clinical speech perception scores explained competition with phonologically related words.

Conclusions: The general analysis of CI users’ lexical competition patterns showed merely quantitative differences with NH listeners in the time course of lexical competition, but our additional analysis revealed more qualitative differences in CI users’ strategies to process speech. Individuals’ word–nonword sensitivity explained different parts of individual variability than clinical speech perception scores. These results stress, particularly for heterogeneous clinical populations such as CI users, the importance of investigating individual differences in addition to group averages, as they can be informative for clinical rehabilitation.

Supplemental Material S1. An overview of the word and nonword characteristics of the stimuli that were used for the auditory lexical decision task (Experiment 1).

Supplemental Material S2. Table with the coefficients of the best fitting model of participants’ accuracy scores for the auditory lexical decision task (Experiment 1).

Supplemental Material S3. Table with the coefficients of the best fitting model of participants’ reaction times for the auditory lexical decision task (Experiment 1).

Supplemental Material S4. Table with the coefficients of the best fitting model for fixations towards the phonological competitor (Experiment 2).

Supplemental Material S5. Table with the coefficients of the best fitting model for fixations towards the semantic competitor (Experiment 2).

Supplemental Material S6. Table with the coefficients of the best fitting model for fixations towards the phonological competitor by the subgroup of CI users (Experiment 2).

Supplemental Material S7. Table with the coefficients of the best fitting model for fixations towards the semantic competitor by the subgroup of CI users (Experiment 2).

Nagels, L., Bastiaanse, R., Başkent, D., & Wagner, A. (2019). Individual differences in lexical access among cochlear implant users. Journal of Speech, Language, and Hearing Research. Advance online publication. https://doi.org/10.1044/2019_JSLHR-19-00192