Younger and older adults show non-linear, stimulus-dependent performance during early stages of auditory training for non-native English.

Older adults often report difficulty understanding speech produced by non-native talkers. These listeners can achieve rapid adaptation to non-native speech, but few studies have assessed auditory training protocols to improve non-native speech recognition in older adults. In this study, a word-level training paradigm was employed, targeting improved recognition of Spanish-accented English. Younger and older adults were trained on Spanish-accented monosyllabic word pairs containing four phonemic contrasts (initial s/z, initial f/v, final b/p, final d/t) produced in English by multiple male native Spanish speakers. Listeners completed pre-testing, training, and post-testing over two sessions. Statistical methods, such as growth curve modeling and generalized additive mixed models, were employed to describe the patterns of rapid adaptation and how they varied between listener groups and phonemic contrasts. While the training protocol failed to elicit post-test improvements for recognition of Spanish-accented speech, examination of listeners' performance during the pre-testing period showed patterns of rapid adaptation that differed, depending on the nature of the phonemes to be learned and the listener group. Normal-hearing younger and older adults showed a faster rate of adaptation for non-native stimuli that were more nativelike in their productions, while older adults with hearing impairment did not realize this benefit.

Effects of listener age and native language on perception of accented and unaccented sentences.

Degradations to auditory input have deleterious effects on speech recognition performance, especially by older listeners. Alterations to timing information in speech, such as occurs in rapid or foreign-accented speech, can be particularly difficult for older people to resolve. It is currently unclear how prior language experience modulates performance with temporally altered sentence-length speech utterances. The principal hypothesis is that prior experience with a foreign language affords an advantage for recognition of accented English when the talker and listener share the same native language, which may minimize age-related differences in performance with temporally altered speech. A secondary hypothesis is that native language experience with a syllable-timed language (Spanish) is advantageous for recognizing rapid English speech. Native speakers of English and Spanish completed speech recognition tasks with both accented and unaccented English sentences presented in various degrees of time compression (TC). Native English listeners showed higher or equivalent recognition of accented and unaccented English speech compared to native Spanish listeners in all TC conditions. Additionally, significant effects of aging were seen for native Spanish listeners on all tasks. Overall, the results did not support the hypotheses for a benefit of shared language experience for non-native speakers of English, particularly older native Spanish listeners.

Recognition of asynchronous auditory-visual speech by younger and older listeners: A preliminary study.

This study examined the effects of age and hearing loss on recognition of speech presented when the auditory and visual speech information was misaligned in time (i.e., asynchronous). Prior research suggests that older listeners are less sensitive than younger listeners in detecting the presence of asynchronous speech for auditory-lead conditions, but recognition of speech in auditory-lead conditions has not yet been examined. Recognition performance was assessed for sentences and words presented in the auditory-visual modalities with varying degrees of auditory lead and lag. Detection of auditory-visual asynchrony for sentences was assessed to verify that listeners detected these asynchronies. The listeners were younger and older normal-hearing adults and older hearing-impaired adults. Older listeners (regardless of hearing status) exhibited a significant decline in performance in auditory-lead conditions relative to visual lead, unlike younger listeners whose recognition performance was relatively stable across asynchronies. Recognition performance was not correlated with asynchrony detection. However, one of the two cognitive measures assessed, processing speed, was identified in multiple regression analyses as contributing significantly to the variance in auditory-visual speech recognition scores. The findings indicate that, particularly in auditory-lead conditions, listener age has an impact on the ability to recognize asynchronous auditory-visual speech signals.

Perception of contrastive bi-syllabic lexical stress in unaccented and accented words by younger and older listeners.

This study examined the ability of older and younger listeners to perceive contrastive syllable stress in unaccented and Spanish-accented cognate bi-syllabic English words. Younger listeners with normal hearing, older listeners with normal hearing, and older listeners with hearing impairment judged recordings of words that contrasted in stress that conveyed a noun or verb form (e.g., CONduct/conDUCT), using two paradigms differing in the amount of semantic support. The stimuli were spoken by four speakers: one native English speaker and three Spanish-accented speakers (one moderately and two mildly accented). The results indicate that all listeners showed the lowest accuracy scores in responding to the most heavily accented speaker and the highest accuracy in judging the productions of the native English speaker. The two older groups showed lower accuracy in judging contrastive lexical stress than the younger group, especially for verbs produced by the most accented speaker. This general pattern of performance was observed in the two experimental paradigms, although performance was generally lower in the paradigm without semantic support. The findings suggest that age-related difficulty in adjusting to deviations in contrastive bi-syllabic lexical stress produced with a Spanish accent may be an important factor limiting perception of accented English by older people.

Effects of age and hearing loss on recognition of unaccented and accented multisyllabic words.

The effects of age and hearing loss on recognition of unaccented and accented words of varying syllable length were investigated. It was hypothesized that with increments in length of syllables, there would be atypical alterations in syllable stress in accented compared to native English, and that these altered stress patterns would be sensitive to auditory temporal processing deficits with aging. Sets of one-, two-, three-, and four-syllable words with the same initial syllable were recorded by one native English and two Spanish-accented talkers. Lists of these words were presented in isolation and in sentence contexts to younger and older normal-hearing listeners and to older hearing-impaired listeners. Hearing loss effects were apparent for unaccented and accented monosyllabic words, whereas age effects were observed for recognition of accented multisyllabic words, consistent with the notion that altered syllable stress patterns with accent are sensitive for revealing effects of age. Older listeners also exhibited lower recognition scores for moderately accented words in sentence contexts than in isolation, suggesting that the added demands on working memory for words in sentence contexts impact recognition of accented speech. The general pattern of results suggests that hearing loss, age, and cognitive factors limit the ability to recognize Spanish-accented speech.

Recognition of accented and unaccented speech in different maskers by younger and older listeners.

This investigation examined the effect of accent of target talkers and background speech maskers on listeners' ability to use cues to separate speech from noise. Differences in accent may create a disparity in the relative timing between signal and background, and such timing cues may be used to separate the target talker from the background speech masker. However, the use of this cue could be reduced for older listeners with temporal processing deficits, especially those with hearing loss. Participants were younger and older listeners with normal hearing and older listeners with hearing loss. Stimuli were IEEE sentences recorded in English by male native speakers of English and Spanish. These sentences were presented in different maskers that included speech-modulated noise and background babbles varying in talker gender and accent. Signal-to-noise ratios corresponding to 50% correct performance were measured. Results indicate that a pronounced Spanish accent limits a listener's ability to take advantage of cues to speech segregation and that a difference in accentedness between the target talker and background masker may be a useful cue for speech segregation. Older hearing-impaired listeners performed poorly in all conditions with the accented talkers.

Detection and Recognition of Asynchronous Auditory/Visual Speech: Effects of Age, Hearing Loss, and Talker Accent.

This investigation examined age-related differences in auditory-visual (AV) integration as reflected on perceptual judgments of temporally misaligned AV English sentences spoken by native English and native Spanish talkers. In the detection task, it was expected that slowed auditory temporal processing of older participants, relative to younger participants, would be manifest as a shift in the range over which participants would judge asynchronous stimuli as synchronous (referred to as the "AV simultaneity window"). The older participants were also expected to exhibit greater declines in speech recognition for asynchronous AV stimuli than younger participants. Talker accent was hypothesized to influence listener performance, with older listeners exhibiting a greater narrowing of the AV simultaneity window and much poorer recognition of asynchronous AV foreign-accented speech compared to younger listeners. Participant groups included younger and older participants with normal hearing and older participants with hearing loss. Stimuli were video recordings of sentences produced by native English and native Spanish talkers. The video recordings were altered in 50 ms steps by delaying either the audio or video onset. Participants performed a detection task in which they judged whether the sentences were synchronous or asynchronous, and performed a recognition task for multiple synchronous and asynchronous conditions. Both the detection and recognition tasks were conducted at the individualized signal-to-noise ratio (SNR) corresponding to approximately 70% correct speech recognition performance for synchronous AV sentences. Older listeners with and without hearing loss generally showed wider AV simultaneity windows than younger listeners, possibly reflecting slowed auditory temporal processing in auditory lead conditions and reduced sensitivity to asynchrony in auditory lag conditions. However, older and younger listeners were affected similarly by misalignment of auditory and visual signal onsets on the speech recognition task. This suggests that older listeners are negatively impacted by temporal misalignments for speech recognition, even when they do not notice that the stimuli are asynchronous. Overall, the findings show that when listener performance is equated for simultaneous AV speech signals, age effects are apparent in detection judgments but not in recognition of asynchronous speech.

Recognition of accented English in quiet and noise by younger and older listeners.

This study investigated the effects of age and hearing loss on perception of accented speech presented in quiet and noise. The relative importance of alterations in phonetic segments vs. temporal patterns in a carrier phrase with accented speech also was examined. English sentences recorded by a native English speaker and a native Spanish speaker, together with hybrid sentences that varied the native language of the speaker of the carrier phrase and the final target word of the sentence were presented to younger and older listeners with normal hearing and older listeners with hearing loss in quiet and noise. Effects of age and hearing loss were observed in both listening environments, but varied with speaker accent. All groups exhibited lower recognition performance for the final target word spoken by the accented speaker compared to that spoken by the native speaker, indicating that alterations in segmental cues due to accent play a prominent role in intelligibility. Effects of the carrier phrase were minimal. The findings indicate that recognition of accented speech, especially in noise, is a particularly challenging communication task for older people.

Recognition of accented English in quiet by younger normal-hearing listeners and older listeners with normal-hearing and hearing loss.

This investigation examined the effects of listener age and hearing loss on recognition of accented speech. Speech materials were isolated English words and sentences that featured phonemes that are often mispronounced by non-native speakers of English whose first language is Spanish. These stimuli were recorded by a native speaker of English and two non-native speakers of English: one with a mild accent and one with a moderate accent. The stimuli were presented in quiet to younger and older adults with normal-hearing and older adults with hearing loss. Analysis of percent correct recognition scores showed that all listeners performed more poorly with increasing accent, and older listeners with hearing loss performed more poorly than the younger and older normal-hearing listeners in all accent conditions. Context and age effects were minimal. Consonant confusion patterns in the moderate accent condition showed that error patterns of all listeners reflected temporal alterations with accented speech, with major errors of word-final consonant voicing in stops and fricatives, and word-initial fricatives.

Short-term adaptation to accented English by younger and older adults.

This study examined the effects of age and hearing loss on short-term adaptation to accented speech. Data from younger and older listeners in a prior investigation [Gordon-Salant et al. (2010). J. Acoust. Soc. Am. 128, 444-455] were re-analyzed to examine changes in recognition over four administrations of equivalent lists of English stimuli recorded by native speakers of Spanish and English. Results showed improvement in recognition scores over four list administrations for the accented stimuli but not for the native English stimuli. Group effects emerged but were not involved in any interactions, suggesting that short-term adaptation to accented speech is preserved with aging and with hearing loss.

Effects of Listener Age and Native Language Experience on Recognition of Accented and Unaccented English Words.

Purpose Older native speakers of English have difficulty in understanding Spanish-accented English compared to younger native English speakers. However, it is unclear if this age effect would be observed among native speakers of Spanish. The current study investigates the effects of age and native language experience with Spanish on the ability to recognize words spoken in English by Spanish-accented and unaccented talkers. Method English monosyllabic words, recorded by native speakers of English and Spanish, were presented to 4 groups of listeners with normal hearing: younger native Spanish listeners ( n = 15), older native Spanish listeners ( n = 16), younger native English listeners ( n = 15), and older native English listeners ( n = 15). Speech recognition accuracy was assessed for the unaccented and accented words in both quiet and noise. Results In all conditions, the native English listeners performed better than the native Spanish listeners. More specifically, the native speakers of Spanish consistently recognized accented English less accurately than the native speakers of English, demonstrating no advantage of shared native language experience between nonnative listeners and accented talkers. Older listeners in the native Spanish language group also performed less accurately than their younger counterparts, for English words spoken by both unaccented and accented talkers. Finally, whereas listeners who were native speakers of English showed marked declines in recognition of Spanish-accented English relative to unaccented English, listeners who were native speakers of Spanish (both younger and older) showed less decline. Conclusions The general pattern of results suggests that both native language experience in a language other than English and age limit the ability to recognize Spanish-accented English. The implication of the overall findings is that older nonnative listeners will have considerable difficulty in understanding English, regardless of the talker's accent, in both clinical and everyday listening situations.

The role of temporal cues in word identification by younger and older adults: effects of sentence context.

Prior investigations, using isolated words as stimuli, have shown that older listeners tend to require longer temporal cues than younger listeners to switch their percept from one word to its phonetically contrasting counterpart. The extent to which this age effect occurs in sentence contexts is investigated in the present study. The hypothesis was that perception of temporal cues differs for words presented in isolation and a sentence context and that this effect may vary between younger and older listeners. Younger and older listeners with normal-hearing and older listeners with hearing loss identified phonetically contrasting word pairs in natural speech continua that varied by a single temporal cue: voice-onset time, vowel duration, transition duration, and silent interval duration. The words were presented in isolation and in sentences. A context effect was shown for most continua, in which listeners required longer temporal cues in sentences than in isolated words. Additionally, older listeners required longer cues at the crossover points than younger listeners for most but not all continua. In general, the findings support the conclusion that older listeners tend to require longer target temporal cues than younger normal-hearing listeners in identifying phonetically contrasting word pairs in isolation and sentence contexts.

Age-related differences in identification and discrimination of temporal cues in speech segments.

This study investigated age-related differences in sensitivity to temporal cues in modified natural speech sounds. Listeners included young noise-masked subjects, elderly normal-hearing subjects, and elderly hearing-impaired subjects. Four speech continua were presented to listeners, with stimuli from each continuum varying in a single temporal dimension. The acoustic cues varied in separate continua were voice-onset time, vowel duration, silence duration, and transition duration. In separate conditions, the listeners identified the word stimuli, discriminated two stimuli in a same-different paradigm, and discriminated two stimuli in a 3-interval, 2-alternative forced-choice procedure. Results showed age-related differences in the identification function crossover points for the continua that varied in silence duration and transition duration. All listeners demonstrated shorter difference limens (DLs) for the three-interval paradigm than the two-interval paradigm, with older hearing-impaired listeners showing larger DLs than the other listener groups for the silence duration cue. The findings support the general hypothesis that aging can influence the processing of specific temporal cues that are related to consonant manner distinctions.