The Effort of Repairing a Misperceived Word Can Impair Perception of Following Words, Especially for Listeners With Cochlear Implants.

OBJECTIVES: In clinical and laboratory settings, speech recognition is typically assessed in a way that cannot distinguish accurate auditory perception from misperception that was mentally repaired or inferred from context. Previous work showed that the process of repairing misperceptions elicits greater listening effort, and that this elevated effort lingers well after the sentence is heard. That result suggests that cognitive repair strategies might appear successful when testing a single utterance but fail for everyday continuous conversational speech. The present study tested the hypothesis that the effort of repairing misperceptions has the consequence of carrying over to interfere with perception of later words after the sentence. DESIGN: Stimuli were open-set coherent sentences that were presented intact or with a word early in the sentence replaced with noise, forcing the listener to use later context to mentally repair the missing word. Sentences were immediately followed by digit triplets, which served to probe carryover effort from the sentence. Control conditions allowed for the comparison to intact sentences that did not demand mental repair, as well as to listening conditions that removed the need to attend to the post-sentence stimuli, or removed the post-sentence digits altogether. Intelligibility scores for the sentences and digits were accompanied by time-series measurements of pupil dilation to assess cognitive load during the task, as well as subjective rating of effort. Participants included adults with cochlear implants (CIs), as well as an age-matched group and a younger group of listeners with typical hearing for comparison. RESULTS: For the CI group, needing to repair a missing word during a sentence resulted in more errors on the digits after the sentence, especially when the repair process did not result in a coherent sensible perception. Sentences that needed repair also contained more errors on the words that were unmasked. All groups showed substantial increase of pupil dilation when sentences required repair, even when the repair was successful. Younger typical hearing listeners showed clear differences in moment-to-moment allocation of effort in the different conditions, while the other groups did not. CONCLUSIONS: For CI listeners, the effort of needing to repair misperceptions in a sentence can last long enough to interfere with words that follow the sentence. This pattern could pose a serious problem for regular communication but would go overlooked in typical testing with single utterances, where a listener has a chance to repair misperceptions before responding. Carryover effort was not predictable by basic intelligibility scores, but can be revealed in behavioral data when sentences are followed immediately by extra probe words such as digits.

How to vocode: Using channel vocoders for cochlear-implant research.

The channel vocoder has become a useful tool to understand the impact of specific forms of auditory degradation-particularly the spectral and temporal degradation that reflect cochlear-implant processing. Vocoders have many parameters that allow researchers to answer questions about cochlear-implant processing in ways that overcome some logistical complications of controlling for factors in individual cochlear implant users. However, there is such a large variety in the implementation of vocoders that the term "vocoder" is not specific enough to describe the signal processing used in these experiments. Misunderstanding vocoder parameters can result in experimental confounds or unexpected stimulus distortions. This paper highlights the signal processing parameters that should be specified when describing vocoder construction. The paper also provides guidance on how to determine vocoder parameters within perception experiments, given the experimenter's goals and research questions, to avoid common signal processing mistakes. Throughout, we will assume that experimenters are interested in vocoders with the specific goal of better understanding cochlear implants.

A Large-Scale Study of the Relationship Between Degree and Type of Hearing Loss and Recognition of Speech in Quiet and Noise.

OBJECTIVES: Understanding speech in noise (SIN) is the dominant complaint of individuals with hearing loss. For decades, the default test of speech perception in routine audiologic assessment has been monosyllabic word recognition in quiet (WRQ), which does not directly address patient concerns, leading some to advocate that measures of SIN should be integrated into routine practice. However, very little is known with regard to how SIN abilities are affected by different types of hearing loss. Here, we examine performance on clinical measures of WRQ and SIN in a large patient base consisting of a variety of hearing loss types, including conductive (CHL), mixed (MHL), and sensorineural (SNHL) losses. DESIGN: In a retrospective study, we examined data from 5593 patients (51% female) who underwent audiometric assessment at the Stanford Ear Institute. All individuals completed pure-tone audiometry, and speech perception testing of monaural WRQ, and monaural QuickSIN. Patient ages ranged from 18 to 104 years (average = 57). The average age in years for the different classifications of hearing loss was 51.1 (NH), 48.5 (CHL), 64.2 (MHL), and 68.5 (SNHL), respectively. Generalized linear mixed-effect models and quartile regression were used to determine the relationship between hearing loss type and severity for the different speech-recognition outcome measures. RESULTS: Patients with CHL had similar performance to patients with normal hearing on both WRQ and QuickSIN, regardless of the hearing loss severity. In patients with MHL or SNHL, WRQ scores remained largely excellent with increasing hearing loss until the loss was moderately severe or worse. In contrast, QuickSIN signal to noise ratio (SNR) losses showed an orderly systematic decrease as the degree of hearing loss became more severe. This effect scaled with the data, with threshold-QuickSIN relationships absent for CHL, and becoming increasingly stronger for MHL and strongest in patients with SNHL. However, the variability in these data suggests that only 57% of the variance in WRQ scores, and 50% of the variance in QuickSIN SNR losses, could be accounted for by the audiometric thresholds. Patients who would not be differentiated by WRQ scores are shown to be potentially differentiable by SIN scores. CONCLUSIONS: In this data set, conductive hearing loss had little effect on WRQ scores or QuickSIN SNR losses. However, for patients with MHL or SNHL, speech perception abilities decreased as the severity of the hearing loss increased. In these data, QuickSIN SNR losses showed deficits in performance with degrees of hearing loss that yielded largely excellent WRQ scores. However, the considerable variability in the data suggests that even after classifying patients according to their type of hearing loss, hearing thresholds only account for a portion of the variance in speech perception abilities, particularly in noise. These results are consistent with the idea that variables such as cochlear health and aging add explanatory power over audibility alone.

Time Scales and Moments of Listening Effort Revealed in Pupillometry.

This article offers a collection of observations that highlight the value of time course data in pupillometry and points out ways in which these observations create deeper understanding of listening effort. The main message is that listening effort should be considered on a moment-to-moment basis rather than as a singular amount. A review of various studies and the reanalysis of data reveal distinct signatures of effort before a stimulus, during a stimulus, in the moments after a stimulus, and changes over whole experimental testing sessions. Collectively these observations motivate questions that extend beyond the "amount" of effort, toward understanding how long the effort lasts, and how precisely someone can allocate effort at specific points in time or reduce effort at other times. Apparent disagreements between studies are reconsidered as informative lessons about stimulus selection and the nature of pupil dilation as a reflection of decision making rather than the difficulty of sensory encoding.

Reconsidering classic ideas in speech communication.

The papers in this special issue provide a critical look at some historical ideas that have had an influence on research and teaching in the field of speech communication. They also address widely used methodologies or address long-standing methodological challenges in the areas of speech perception and speech production. The goal is to reconsider and evaluate the need for caution or replacement of historical ideas with more modern results and methods. The contributions provide respectful historical context to the classic ideas, as well as new original research or discussion that clarifies the limitations of the original ideas.

Identifying Listeners Whose Speech Intelligibility Depends on a Quiet Extra Moment After a Sentence.

PURPOSE: An extra moment after a sentence is spoken may be important for listeners with hearing loss to mentally repair misperceptions during listening. The current audiologic test battery cannot distinguish between a listener who repaired a misperception versus a listener who heard the speech accurately with no need for repair. This study aims to develop a behavioral method to identify individuals who are at risk for relying on a quiet moment after a sentence. METHOD: Forty-three individuals with hearing loss (32 cochlear implant users, 11 hearing aid users) heard sentences that were followed by either 2 s of silence or 2 s of babble noise. Both high- and low-context sentences were used in the task. RESULTS: Some individuals showed notable benefit in accuracy scores (particularly for high-context sentences) when given an extra moment of silent time following the sentence. This benefit was highly variable across individuals and sometimes absent altogether. However, the group-level patterns of results were mainly explained by the use of context and successful perception of the words preceding sentence-final words. CONCLUSIONS: These results suggest that some but not all individuals improve their speech recognition score by relying on a quiet moment after a sentence, and that this fragility of speech recognition cannot be assessed using one isolated utterance at a time. Reliance on a quiet moment to repair perceptions would potentially impede the perception of an upcoming utterance, making continuous communication in real-world scenarios difficult especially for individuals with hearing loss. The methods used in this study-along with some simple modifications if necessary-could potentially identify patients with hearing loss who retroactively repair mistakes by using clinically feasible methods that can ultimately lead to better patient-centered hearing health care. SUPPLEMENTAL MATERIAL: https://doi.org/10.23641/asha.21644801.

Strategic perceptual weighting of acoustic cues for word stress in listeners with cochlear implants, acoustic hearing, or simulated bimodal hearing.

Perception of word stress is an important aspect of recognizing speech, guiding the listener toward candidate words based on the perceived stress pattern. Cochlear implant (CI) signal processing is likely to disrupt some of the available cues for word stress, particularly vowel quality and pitch contour changes. In this study, we used a cue weighting paradigm to investigate differences in stress cue weighting patterns between participants listening with CIs and those with normal hearing (NH). We found that participants with CIs gave less weight to frequency-based pitch and vowel quality cues than NH listeners but compensated by upweighting vowel duration and intensity cues. Nonetheless, CI listeners' stress judgments were also significantly influenced by vowel quality and pitch, and they modulated their usage of these cues depending on the specific word pair in a manner similar to NH participants. In a series of separate online experiments with NH listeners, we simulated aspects of bimodal hearing by combining low-pass filtered speech with a vocoded signal. In these conditions, participants upweighted pitch and vowel quality cues relative to a fully vocoded control condition, suggesting that bimodal listening holds promise for restoring the stress cue weighting patterns exhibited by listeners with NH.

Reconsidering commonly used stimuli in speech perception experiments.

This paper examines some commonly used stimuli in speech perception experiments and raises questions about their use, or about the interpretations of previous results. The takeaway messages are: 1) the Hillenbrand vowels represent a particular dialect rather than a gold standard, and English vowels contain spectral dynamics that have been largely underappreciated, 2) the /ɑ/ context is very common but not clearly superior as a context for testing consonant perception, 3) /ɑ/ is particularly problematic when testing voice-onset-time perception because it introduces strong confounds in the formant transitions, 4) /dɑ/ is grossly overrepresented in neurophysiological studies and yet is insufficient as a generalized proxy for "speech perception," and 5) digit tests and matrix sentences including the coordinate response measure are systematically insensitive to important patterns in speech perception. Each of these stimulus sets and concepts is described with careful attention to their unique value and also cases where they might be misunderstood or over-interpreted.

Effortful Listening Despite Correct Responses: The Cost of Mental Repair in Sentence Recognition by Listeners With Cochlear Implants.

PURPOSE: Speech recognition percent correct scores fail to capture the effort of mentally repairing the perception of speech that was initially misheard. This study measured the effort of listening to stimuli specifically designed to elicit mental repair in adults who use cochlear implants (CIs). METHOD: CI listeners heard and repeated sentences in which specific words were distorted or masked by noise but recovered based on later context: a signature of mental repair. Changes in pupil dilation were tracked as an index of effort and time-locked with specific landmarks during perception. RESULTS: Effort significantly increases when a listener needs to repair a misperceived word, even if the verbal response is ultimately correct. Mental repair of words in a sentence was accompanied by greater prevalence of errors elsewhere in the same sentence, suggesting that effort spreads to consume resources across time. The cost of mental repair in CI listeners was essentially the same as that observed in listeners with normal hearing in previous work. CONCLUSIONS: Listening effort as tracked by pupil dilation is better explained by the mental repair and reconstruction of words rather than the appearance of correct or incorrect perception. Linguistic coherence drives effort more heavily than the mere presence of mistakes, highlighting the importance of testing materials that do not constrain coherence by design.

Distortion of Spectral Ripples Through Cochlear Implants Has Major Implications for Interpreting Performance Scores.

The spectral ripple discrimination task is a psychophysical measure that has been found to correlate with speech recognition in listeners with cochlear implants (CIs). However, at ripple densities above a critical value (around 2 RPO, but device-specific), the sparse spectral sampling of CI processors results in stimulus distortions resulting in aliasing and unintended changes in modulation depth. As a result, spectral ripple thresholds above a certain number are not ordered monotonically along the RPO dimension and thus cannot be considered better or worse spectral resolution than each other, thus undermining correlation measurements. These stimulus distortions are not remediated by changing stimulus phase, indicating these issues cannot be solved by spectrotemporally modulated stimuli. Speech generally has very low-density spectral modulations, leading to questions about the mechanism of correlation between high ripple thresholds and speech recognition. Existing data showing correlations between ripple discrimination and speech recognition include many observations above the aliasing limit. These scores should be treated with caution, and experimenters could benefit by prospectively considering the limitations of the spectral ripple test.

Listening Effort Is Not the Same as Speech Intelligibility Score.

Listening effort is a valuable and important notion to measure because it is among the primary complaints of people with hearing loss. It is tempting and intuitive to accept speech intelligibility scores as a proxy for listening effort, but this link is likely oversimplified and lacks actionable explanatory power. This study was conducted to explain the mechanisms of listening effort that are not captured by intelligibility scores, using sentence-repetition tasks where specific kinds of mistakes were prospectively planned or analyzed retrospectively. Effort measured as changes in pupil size among 20 listeners with normal hearing and 19 listeners with cochlear implants. Experiment 1 demonstrates that mental correction of misperceived words increases effort even when responses are correct. Experiment 2 shows that for incorrect responses, listening effort is not a function of the proportion of words correct but is rather driven by the types of errors, position of errors within a sentence, and the need to resolve ambiguity, reflecting how easily the listener can make sense of a perception. A simple taxonomy of error types is provided that is both intuitive and consistent with data from these two experiments. The diversity of errors in these experiments implies that speech perception tasks can be designed prospectively to elicit the mistakes that are more closely linked with effort. Although mental corrective action and number of mistakes can scale together in many experiments, it is possible to dissociate them to advance toward a more explanatory (rather than correlational) account of listening effort.

Individual Variability in Recalibrating to Spectrally Shifted Speech: Implications for Cochlear Implants.

OBJECTIVES: Cochlear implant (CI) recipients are at a severe disadvantage compared with normal-hearing listeners in distinguishing consonants that differ by place of articulation because the key relevant spectral differences are degraded by the implant. One component of that degradation is the upward shifting of spectral energy that occurs with a shallow insertion depth of a CI. The present study aimed to systematically measure the effects of spectral shifting on word recognition and phoneme categorization by specifically controlling the amount of shifting and using stimuli whose identification specifically depends on perceiving frequency cues. We hypothesized that listeners would be biased toward perceiving phonemes that contain higher-frequency components because of the upward frequency shift and that intelligibility would decrease as spectral shifting increased. DESIGN: Normal-hearing listeners (n = 15) heard sine wave-vocoded speech with simulated upward frequency shifts of 0, 2, 4, and 6 mm of cochlear space to simulate shallow CI insertion depth. Stimuli included monosyllabic words and /b/-/d/ and /∫/-/s/ continua that varied systematically by formant frequency transitions or frication noise spectral peaks, respectively. Recalibration to spectral shifting was operationally defined as shifting perceptual acoustic-phonetic mapping commensurate with the spectral shift. In other words, adjusting frequency expectations for both phonemes upward so that there is still a perceptual distinction, rather than hearing all upward-shifted phonemes as the higher-frequency member of the pair. RESULTS: For moderate amounts of spectral shifting, group data suggested a general "halfway" recalibration to spectral shifting, but individual data suggested a notably different conclusion: half of the listeners were able to recalibrate fully, while the other halves of the listeners were utterly unable to categorize shifted speech with any reliability. There were no participants who demonstrated a pattern intermediate to these two extremes. Intelligibility of words decreased with greater amounts of spectral shifting, also showing loose clusters of better- and poorer-performing listeners. Phonetic analysis of word errors revealed certain cues were more susceptible to being compromised due to a frequency shift (place and manner of articulation), while voicing was robust to spectral shifting. CONCLUSIONS: Shifting the frequency spectrum of speech has systematic effects that are in line with known properties of speech acoustics, but the ensuing difficulties cannot be predicted based on tonotopic mismatch alone. Difficulties are subject to substantial individual differences in the capacity to adjust acoustic-phonetic mapping. These results help to explain why speech recognition in CI listeners cannot be fully predicted by peripheral factors like electrode placement and spectral resolution; even among listeners with functionally equivalent auditory input, there is an additional factor of simply being able or unable to flexibly adjust acoustic-phonetic mapping. This individual variability could motivate precise treatment approaches guided by an individual's relative reliance on wideband frequency representation (even if it is mismatched) or limited frequency coverage whose tonotopy is preserved.

Slower Speaking Rate Reduces Listening Effort Among Listeners With Cochlear Implants.

OBJECTIVES: Slowed speaking rate was examined for its effects on speech intelligibility, its interaction with the benefit of contextual cues, and the impact of these factors on listening effort in adults with cochlear implants. DESIGN: Participants (n = 21 cochlear implant users) heard high- and low-context sentences that were played at the original speaking rate, as well as a slowed (1.4× duration) speaking rate, using uniform pitch-synchronous time warping. In addition to intelligibility measures, changes in pupil dilation were measured as a time-varying index of processing load or listening effort. Slope of pupil size recovery to baseline after the sentence was used as an index of resolution of perceptual ambiguity. RESULTS: Speech intelligibility was better for high-context compared to low-context sentences and slightly better for slower compared to original-rate speech. Speech rate did not affect magnitude and latency of peak pupil dilation relative to sentence offset. However, baseline pupil size recovered more substantially for slower-rate sentences, suggesting easier processing in the moment after the sentence was over. The effect of slowing speech rate was comparable to changing a sentence from low context to high context. The effect of context on pupil dilation was not observed until after the sentence was over, and one of two analyses suggested that context had greater beneficial effects on listening effort when the speaking rate was slower. These patterns maintained even at perfect sentence intelligibility, suggesting that correct speech repetition does not guarantee efficient or effortless processing. With slower speaking rates, there was less variability in pupil dilation slopes following the sentence, implying mitigation of some of the difficulties shown by individual listeners who would otherwise demonstrate prolonged effort after a sentence is heard. CONCLUSIONS: Slowed speaking rate provides release from listening effort when hearing an utterance, particularly relieving effort that would have lingered after a sentence is over. Context arguably provides even more release from listening effort when speaking rate is slower. The pattern of prolonged pupil dilation for faster speech is consistent with increased need to mentally correct errors, although that exact interpretation cannot be verified with intelligibility data alone or with pupil data alone. A pattern of needing to dwell on a sentence to disambiguate misperceptions likely contributes to difficulty in running conversation where there are few opportunities to pause and resolve recently heard utterances.

Perceptual weighting of acoustic cues for accommodating gender-related talker differences heard by listeners with normal hearing and with cochlear implants.

Listeners must accommodate acoustic differences between vocal tracts and speaking styles of conversation partners-a process called normalization or accommodation. This study explores what acoustic cues are used to make this perceptual adjustment by listeners with normal hearing or with cochlear implants, when the acoustic variability is related to the talker's gender. A continuum between /ʃ/ and /s/ was paired with naturally spoken vocalic contexts that were parametrically manipulated to vary by numerous cues for talker gender including fundamental frequency (F0), vocal tract length (formant spacing), and direct spectral contrast with the fricative. The goal was to examine relative contributions of these cues toward the tendency to have a lower-frequency acoustic boundary for fricatives spoken by men (found in numerous previous studies). Normal hearing listeners relied primarily on formant spacing and much less on F0. The CI listeners were individually variable, with the F0 cue emerging as the strongest cue on average.

Sensitivity to binaural temporal-envelope beats with single-sided deafness and a cochlear implant as a measure of tonotopic match (L).

For cochlear-implant users with near-normal contralateral hearing, a mismatch between the frequency-to-place mapping in the two ears could produce a suboptimal performance. This study assesses tonotopic matches via binaural interactions. Dynamic interaural time-difference sensitivity was measured using bandpass-filtered pulse trains at different rates in the acoustic and implanted ear, creating binaural envelope beats. Sensitivity to beats should peak when the same tonotopic region is stimulated in both ears. All nine participants detected dynamic interaural timing differences and demonstrated some frequency selectivity. This method provides a guide to frequency-to-place mapping without compensation for inherent latency differences between the acoustic and implanted ears.

Effects of Age and Cochlear Implantation on Spectrally Cued Speech Categorization.

Purpose Weighting of acoustic cues for perceiving place-of-articulation speech contrasts was measured to determine the separate and interactive effects of age and use of cochlear implants (CIs). It has been found that adults with normal hearing (NH) show reliance on fine-grained spectral information (e.g., formants), whereas adults with CIs show reliance on broad spectral shape (e.g., spectral tilt). In question was whether children with NH and CIs would demonstrate the same patterns as adults, or show differences based on ongoing maturation of hearing and phonetic skills. Method Children and adults with NH and with CIs categorized a /b/-/d/ speech contrast based on two orthogonal spectral cues. Among CI users, phonetic cue weights were compared to vowel identification scores and Spectral-Temporally Modulated Ripple Test thresholds. Results NH children and adults both relied relatively more on the fine-grained formant cue and less on the broad spectral tilt cue compared to participants with CIs. However, early-implanted children with CIs better utilized the formant cue compared to adult CI users. Formant cue weights correlated with CI participants' vowel recognition and in children, also related to Spectral-Temporally Modulated Ripple Test thresholds. Adults and child CI users with very poor phonetic perception showed additive use of the two cues, whereas those with better and/or more mature cue usage showed a prioritized trading relationship, akin to NH listeners. Conclusions Age group and hearing modality can influence phonetic cue-weighting patterns. Results suggest that simple nonlexical categorization tests correlate with more general speech recognition skills of children and adults with CIs.

GazeR: A Package for Processing Gaze Position and Pupil Size Data.

Eye-tracking is widely used throughout the scientific community, from vision science and psycholinguistics to marketing and human-computer interaction. Surprisingly, there is little consistency and transparency in preprocessing steps, making replicability and reproducibility difficult. To increase replicability, reproducibility, and transparency, a package in R (a free and widely used statistical programming environment) called gazeR was created to read and preprocess two types of data: gaze position and pupil size. For gaze position data, gazeR has functions for reading in raw eye-tracking data, formatting it for analysis, converting from gaze coordinates to areas of interest, and binning and aggregating data. For data from pupillometry studies, the gazeR package has functions for reading in and merging multiple raw pupil data files, removing observations with too much missing data, eliminating artifacts, blink identification and interpolation, subtractive baseline correction, and binning and aggregating data. The package is open-source and freely available for download and installation: https://github.com/dmirman/gazer . We provide step-by-step analyses of data from two tasks exemplifying the package's capabilities.

Manipulation of voice onset time in speech stimuli: A tutorial and flexible Praat script.

Voice onset time (VOT) is an acoustic property of stop consonants that is commonly manipulated in studies of phonetic perception. This paper contains a thorough description of the "progressive cutback and replacement" method of VOT manipulation, and comparison with other VOT manipulation techniques. Other acoustic properties that covary with VOT-such as fundamental frequency and formant transitions-are also discussed, along with considerations for testing VOT perception and its relationship to various other measures of auditory temporal or spectral processing. An implementation of the progressive cutback and replacement method in the Praat scripting language is presented, which is suitable for modifying natural speech for perceptual experiments involving VOT and/or related covarying F0 and intensity cues. Justifications are provided for the stimulus design choices and constraints implemented in the script.

Accommodation of gender-related phonetic differences by listeners with cochlear implants and in a variety of vocoder simulations.

Speech perception requires accommodation of a wide range of acoustic variability across talkers. A classic example is the perception of "sh" and "s" fricative sounds, which are categorized according to spectral details of the consonant itself, and also by the context of the voice producing it. Because women's and men's voices occupy different frequency ranges, a listener is required to make a corresponding adjustment of acoustic-phonetic category space for these phonemes when hearing different talkers. This pattern is commonplace in everyday speech communication, and yet might not be captured in accuracy scores for whole words, especially when word lists are spoken by a single talker. Phonetic accommodation for fricatives "s" and "sh" was measured in 20 cochlear implant (CI) users and in a variety of vocoder simulations, including those with noise carriers with and without peak picking, simulated spread of excitation, and pulsatile carriers. CI listeners showed strong phonetic accommodation as a group. Each vocoder produced phonetic accommodation except the 8-channel noise vocoder, despite its historically good match with CI users in word intelligibility. Phonetic accommodation is largely independent of linguistic factors and thus might offer information complementary to speech intelligibility tests which are partially affected by language processing.

Lexical bias in word recognition by cochlear implant listeners.

When hearing an ambiguous speech sound, listeners show a tendency to perceive it as a phoneme that would complete a real word, rather than completing a nonsense/fake word. For example, a sound that could be heard as either /b/ or /É¡/ is perceived as /b/ when followed by _ack but perceived as /É¡/ when followed by "_ap." Because the target sound is acoustically identical across both environments, this effect demonstrates the influence of top-down lexical processing in speech perception. Degradations in the auditory signal were hypothesized to render speech stimuli more ambiguous, and therefore promote increased lexical bias. Stimuli included three speech continua that varied by spectral cues of varying speeds, including stop formant transitions (fast), fricative spectra (medium), and vowel formants (slow). Stimuli were presented to listeners with cochlear implants (CIs), and also to listeners with normal hearing with clear spectral quality, or with varying amounts of spectral degradation using a noise vocoder. Results indicated an increased lexical bias effect with degraded speech and for CI listeners, for whom the effect size was related to segment duration. This method can probe an individual's reliance on top-down processing even at the level of simple lexical/phonetic perception.