Though much is known about how words are recognized, little research has focused on how a degraded signal affects the fine-grained temporal aspects of real-time word recognition. The perception of degraded speech was examined in two populations with the goal of describing the time course of word recognition and lexical competition. Thirty-three postlingually-deafened cochlear implant (CI) users and 57 normal hearing (NH) adults (16 in a CI-simulation condition) participated in a visual world paradigm eye-tracking task in which their fixations to a set of phonologically related items were monitored as they heard one item being named. Each degraded-speech group was compared to a set of age-matched NH participants listening to unfiltered speech. CI users and the simulation group showed a delay in activation relative to the NH listeners, and there is weak evidence that the CI users showed differences in the degree of peak and late competitor activation. In general, though, the degraded-speech groups behaved statistically similarly with respect to activation levels.

This study investigated the developmental timecourse of spoken word recognition in older children using eye-tracking to assess how the real-time processing dynamics of word recognition change over development. We found that nine-year-olds were slower to activate the target words and showed more early competition from competitor words than 16 year olds; however, both age groups ultimately fixated targets to the same degree. This contrasts with a prior study of adolescents with language impairment (McMurray et al, 2010) which showed a different pattern of real-time processes. These findings suggest that the dynamics of word recognition are still developing even at these late ages, and differences due to developmental change may derive from different sources than individual differences in relative language ability.

Spoken language unfolds over time. Consequently, there are brief periods of ambiguity, when incomplete input can match many possible words. Typical listeners solve this problem by immediately activating multiple candidates which compete for recognition. In two experiments using the visual world paradigm, we examined real-time lexical competition in prelingually deaf cochlear implant (CI) users, and normal hearing (NH) adults listening to severely degraded speech. In Experiment 1, adolescent CI users and NH controls matched spoken words to arrays of pictures including pictures of the target word and phonological competitors. Eye-movements to each referent were monitored as a measure of how strongly that candidate was considered over time. Relative to NH controls, CI users showed a large delay in fixating any object, less competition from onset competitors (e.g., sandwich after hearing sandal), and increased competition from rhyme competitors (e.g., candle after hearing sandal). Experiment 2 observed the same pattern with NH listeners hearing highly degraded speech. These studies suggests that in contrast to all prior studies of word recognition in typical listeners, listeners recognizing words in severely degraded conditions can exhibit a substantively different pattern of dynamics, waiting to begin lexical access until substantial information has accumulated.

Purpose Researchers have begun to use eye tracking in the visual world paradigm (VWP) to study clinical differences in language processing, but the reliability of such laboratory tests has rarely been assessed. This paper assesses test-retest reliability of the VWP for spoken word recognition. Methods Participants performed an auditory VWP task in repeated sessions and a visual-only VWP task in a third session. We performed correlation and regression analyses on several parameters to determine which reflect reliable behavior and which are predictive of behavior in later sessions. Results Results showed that the fixation parameters most closely related to timing and degree of fixations were moderately-to-strongly correlated across days, while the parameters related to rate of increase or decrease of fixations to particular items were less strongly correlated. Moreover, when including factors derived from the visual-only task, the performance of the regression model was at least moderately correlated with Day 2 performance on all parameters (R > .30). Conclusions The VWP is stable enough (with some caveats) to serve as an individual measure. These findings suggest guidelines for future use of the paradigm and for areas of improvement in both methodology and analysis.

Objectives While outcomes with cochlear implants (CIs) are generally good, performance can be fragile. The authors examined two factors that are crucial for good CI performance. First, while there is a clear benefit for adding residual acoustic hearing to CI stimulation (typically in low frequencies), it is unclear whether this contributes directly to phonetic categorization. Thus, the authors examined perception of voicing (which uses low-frequency acoustic cues) and fricative place of articulation (s/ʃ, which does not) in CI users with and without residual acoustic hearing. Second, in speech categorization experiments, CI users typically show shallower identification functions. These are typically interpreted as deriving from noisy encoding of the signal. However, psycholinguistic work suggests shallow slopes may also be a useful way to adapt to uncertainty. The authors thus employed an eye-tracking paradigm to examine this in CI users. Design Participants were 30 CI users (with a variety of configurations) and 22 age-matched normal hearing (NH) controls. Participants heard tokens from six b/p and six s/ʃ continua (eight steps) spanning real words (e.g., beach/peach, sip/ship). Participants selected the picture corresponding to the word they heard from a screen containing four items (a b-, p-, s- and ʃ-initial item). Eye movements to each object were monitored as a measure of how strongly they were considering each interpretation in the moments leading up to their final percept. Results Mouse-click results (analogous to phoneme identification) for voicing showed a shallower slope for CI users than NH listeners, but no differences between CI users with and without residual acoustic hearing. For fricatives, CI users also showed a shallower slope, but unexpectedly, acoustic + electric listeners showed an even shallower slope. Eye movements showed a gradient response to fine-grained acoustic differences for all listeners. Even considering only trials in which a participant clicked “b” (for example), and accounting for variation in the category boundary, participants made more looks to the competitor (“p”) as the voice onset time neared the boundary. CI users showed a similar pattern, but looked to the competitor more than NH listeners, and this was not different at different continuum steps. Conclusion Residual acoustic hearing did not improve voicing categorization suggesting it may not help identify these phonetic cues. The fact that acoustic + electric users showed poorer performance on fricatives was unexpected as they usually show a benefit in standardized perception measures, and as sibilants contain little energy in the low-frequency (acoustic) range. The authors hypothesize that these listeners may over-weight acoustic input, and have problems when this is not available (in fricatives). Thus, the benefit (or cost) of acoustic hearing for phonetic categorization may be complex. Eye movements suggest that in both CI and NH listeners, phoneme categorization is not a process of mapping continuous cues t...