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Background/Aims:This work examines the perception of the stop voicing contrast in Spanish and English along four acoustic dimensions, comparing monolingual and bilingual listeners. Our primary goals are to test the extent to which cue-weighting strategies are language-specific in monolinguals, and whether this language specificity extends to bilingual listeners.Methods:Participants categorized sounds varying in voice onset time (VOT, the primary cue to the contrast) and three secondary cues: fundamental frequency at vowel onset, first formant (F1) onset frequency, and stop closure duration. Listeners heard acoustically identical target stimuli, within language-specific carrier phrases, in English and Spanish modes.Results:While all listener groups used all cues, monolingual English listeners relied more on F1, and less on closure duration, than monolingual Spanish listeners, indicating language specificity in cue use. Early bilingual listeners used the three secondary cues similarly in English and Spanish, despite showing language-specific VOT boundaries.Conclusion:While our findings reinforce previous work demonstrating language-specific phonetic representations in bilinguals in terms of VOT boundary, they suggest that this specificity may not extend straightforwardly to cue-weighting strategies.

The current work examines native Korean speakers’ perception and production of stop contrasts in their native language (L1, Korean) and second language (L2, English), focusing on three acoustic dimensions that are all used, albeit to different extents, in both languages: voice onset time (VOT), f0 at vowel onset, and closure duration. Participants used all three cues to distinguish the L1 Korean three-way stop distinction in both production and perception. Speakers’ productions of the L2 English contrasts were reliably distinguished using both VOT and f0 (even though f0 is only a very weak cue to the English contrast), and, to a lesser extent, closure duration. In contrast to the relative homogeneity of the L2 productions, group patterns on a forced-choice perception task were less clear-cut, due to considerable individual differences in perceptual categorization strategies, with listeners using either primarily VOT duration, primarily f0, or both dimensions equally to distinguish the L2 English contrast. Differences in perception, which were stable across experimental sessions, were not predicted by individual variation in production patterns. This work suggests that reliance on multiple cues in representation of a phonetic contrast can form the basis for distinct individual cue-weighting strategies in phonetic categorization.

Audition is often treated as a 'secondary' sensory system behind vision in the study of cognitive science. In this review, we focus on three seemingly simple perceptual tasks to demonstrate the complexity of perceptual-cognitive processing involved in everyday audition. After providing a short overview of the characteristics of sound and their neural encoding, we present a description of the perceptual task of segregating multiple sound events that are mixed together in the signal reaching the ears. Then, we discuss the ability to localize the sound source in the environment. Finally, we provide some data and theory on how listeners categorize complex sounds, such as speech. In particular, we present research on how listeners weigh multiple acoustic cues in making a categorization decision. One conclusion of this review is that it is time for auditory cognitive science to be developed to match what has been done in vision in order for us to better understand how humans communicate with speech and music. WIREs Cogni Sci 2011 2 479-489 DOI: 10.1002/wcs.123 For further resources related to this article, please visit the WIREs website.

Purpose This study investigated an account of limited short-term memory capacity for children’s speech perception in noise using a dual-task paradigm. Method Sixty-four normal-hearing children (7–14 years of age) participated in this study. Dual tasks were repeating monosyllabic words presented in noise at 8 dB signal-to-noise ratio and rehearsing sets of 3 or 5 digits for subsequent serial recall. Half of the children were told to allocate their primary attention to word repetition and the other half to remembering digits. Dual-task performance was compared to single-task performance. Limitations in short-term memory demands required for the primary task were measured by dual-task decrements in nonprimary tasks. Results Results revealed that (a) regardless of task priority, no dual-task decrements were found for word recognition, but significant dual-task decrements were found for digit recall; (b) most children did not show the ability to allocate attention preferentially to primary tasks; and (c) younger children (7- to 10-year-olds) demonstrated improved word recognition in the dual-task conditions relative to their single-task performance. Conclusions Seven- to 8-year-old children showed the greatest improvement in word recognition at the expense of the greatest decrement in digit recall during dual tasks. Several possibilities for improved word recognition in the dual-task conditions are discussed.

The operating characteristics of the human auditory system clearly constrain the acoustic content and structure of speech. In addition, many researchers have proposed that the form of speech communication takes advantage of what the general auditory/cognitive system does well. We review here three ways in which general perceptual processes have been purported to influence the form of human speech communication: the need for auditory distinctiveness constraining phonetic inventories; the interactions between encoding/processing of sounds within short temporal windows that may underlie some of the listener’s ability to accommodate variance in speech sounds; and the influence of perceptual learning on the formation and adaptability of phonetic categories. These examples provide demonstrations of the synergistic benefits of studying speech and hearing within an inclusive auditory cognitive neuroscience framework.

Listeners possess a remarkable ability to adapt to acoustic variability in the realization of speech sound categories (e.g., different accents). The current work tests whether non-native listeners adapt their use of acoustic cues in phonetic categorization when they are confronted with changes in the distribution of cues in the input, as native listeners do, and examines to what extent these adaptation patterns are influenced by individual cue-weighting strategies. In line with previous work, native English listeners, who use voice onset time (VOT) as a primary cue to the stop voicing contrast (e.g., 'pa' vs. 'ba'), adjusted their use of f0 (a secondary cue to the contrast) when confronted with a noncanonical "accent" in which the two cues gave conflicting information about category membership. Native Korean listeners' adaptation strategies, while variable, were predictable based on their initial cue weighting strategies. In particular, listeners who used f0 as the primary cue to category membership adjusted their use of VOT (their secondary cue) in response to the noncanonical accent, mirroring the native pattern of "downweighting" a secondary cue. Results suggest that non-native listeners show native-like sensitivity to distributional information in the input and use this information to adjust categorization, just as native listeners do, with the specific trajectory of category adaptation governed by initial cue-weighting strategies.

The ability to integrate and weight information across dimensions is central to perception and is particularly important for speech categorization. The present experiments investigate cue weighting by training participants to categorize sounds drawn from a two-dimensional acoustic space defined by the center frequency (CF) and modulation frequency (MF) of frequency-modulated sine waves. These dimensions were psychophysically matched to be equally discriminable and, in the first experiment, were equally informative for accurate categorization. Nevertheless, listeners' category responses reflected a bias for use of CF. This bias remained even when the informativeness of CF was decreased by shifting distributions to create more overlap in CF. A reversal of weighting (MF over CF) was obtained when distribution variance was increased for CF. These results demonstrate that even when equally informative and discriminable, acoustic cues are not necessarily equally weighted in categorization; listeners exhibit biases when integrating multiple acoustic dimensions. Moreover, changes in weighting strategies can be affected by changes in input distribution parameters. This methodology provides potential insights into acquisition of speech sound categories, particularly second language categories. One implication is that ineffective cue weighting strategies for phonetic categories may be alleviated by manipulating variance of uninformative dimensions in training stimuli.

One of the central findings of speech perception is that identical acoustic signals can be perceived as different speech sounds depending on adjacent speech context. Although these phonetic context effects are ubiquitous in speech perception, their neural mechanisms remain largely unknown. The present work presents a review of recent data suggesting that spectral content of speech mediates phonetic context effects and argues that these effects are likely to be governed by general auditory processes. A descriptive framework known as spectral contrast is presented as a means of interpreting these findings. Finally, and most centrally, four behavioral experiments that begin to delineate the level of the auditory system at which interactions among stimulus components occur are described. Two of these experiments investigate the influence of diotic versus dichotic presentation upon two phonetic context effects. Results indicate that context effects remain even when context is presented to the ear contralateral to that of the target syllable. The other two experiments examine the time course of phonetic context effects by manipulating the silent interval between context and target syllables. These studies reveal that phonetic context effects persist for hundreds of milliseconds. Results are interpreted in terms of auditory mechanism with particular attention to the putative link between auditory enhancement and phonetic context effects.

While human vocalizations generate acoustical energy at frequencies up to (and beyond) 20 kHz, the energy at frequencies above about 5 kHz has traditionally been neglected in speech perception research. The intent of this paper is to review (1) the historical reasons for this research trend and (2) the work that continues to elucidate the perceptual significance of high-frequency energy (HFE) in speech and singing. The historical and physical factors reveal that, while HFE was believed to be unnecessary and/or impractical for applications of interest, it was never shown to be perceptually insignificant. Rather, the main causes for focus on low-frequency energy appear to be because the low-frequency portion of the speech spectrum was seen to be sufficient (from a perceptual standpoint), or the difficulty of HFE research was too great to be justifiable (from a technological standpoint). The advancement of technology continues to overcome concerns stemming from the latter reason. Likewise, advances in our understanding of the perceptual effects of HFE now cast doubt on the first cause. Emerging evidence indicates that HFE plays a more significant role than previously believed, and should thus be considered in speech and voice perception research, especially in research involving children and the hearing impaired.

THE “SPECIALNESS” OF SPEECH As is apparent from reading the first line of nearly any research or review article on speech, the task of perceiving speech sounds is complex and the ease with which humans acquire, produce and perceive these sounds is remarkable. Despite the growing appreciation for the complexity of the perception of music, speech perception remains the most amazing and poorly understood auditory (and, if we may be so bold, perceptual) accomplishments of humans. Over the years, there has been considerable debate on whether this achievement is the result of general perceptual/cognitive mechanisms or “special” processes dedicated to the mapping of speech acoustics to linguistic representations (for reviews see Trout, 2001; Diehl et al., 2004). The most familiar proposal of the “specialness” of speech perception is the various incarnations of the Motor Theory of speech proposed by Liberman et al. (1967; Liberman and Mattingly, 1985, 1989). Given the status of research into audition in the 1950s and 1960s, it is not surprising that speech appeared to require processing not available in “normal” hearing. Much of the work at the time used relatively simple tones and noises to get at the basic psychoacoustics underlying the perception of pitch and loudness (though some researchers like Harvey Fletcher were also working on some basics of speech perception, Fletcher and Galt, 1950; Allen, 1996). Liberman and his collaborators discovered that the discrimination of acoustic changes in speech sounds did not look like the psychoacoustic measures of discrimination for pitch and loudness. Instead of following a Weber or Fechner law, the discrimination function had a peak near the categorization boundary between contrasting phonemes—a pattern of perceptual results that is referred to as Categorical Perception (Liberman et al., 1957). In addition, the acoustic cues to phonemic identity were not readily apparent with similar spectral patterns resulting in different phonemic percepts and acoustically disparate patterns resulting in identical phonemic percepts—the problem of “lack of invariance” (e.g., Liberman et al., 1952). The perception of these varying acoustic patterns was highly context-sensitive to preceding and following phonetic content in ways that appeared specific to the communicative constraints of speech and not applicable to the perception of other sounds—as in demonstrations of perceptual compensation for coarticulation, speaking rate normalization and talker normalization (e.g., Ladefoged and Broadbent, 1957; Miller and Liberman, 1979; Mann, 1980). One major source of evidence in favor of a Motor Theory account of speech perception is that information about a speaker’s production (anatomy or kinematics) from non-auditory sources can affect phonetic perception. The famed McGurk effect (McGurk and MacDonald, 1976), in which visual presentation of a talker can alter the auditory phonetic percept, is taken as evidence that listeners are integrating information about production from this secondary source. Fowler and Deckle (1991) have demonstrated a similar effect using haptic information gathered by touching the speaker’s face (see also Sato et al., 2010). Gick and Derrick (2009) reported that perception of consonant— vowel tokens in noise are biased toward voiceless stops (e.g., /pa/) when they are accompanied by a small burst of air on the skin of the listener, which could be interpreted as the aspiration that would more likely accompany the release of a voiceless stop. In addition, there have been several studies that have demonstrated that manipulations of the listener’s articulators can affect perception, which are supportive of the Motor Theory proposal that the mechanisms of production underlie the perception of speech. For example, Ito et al. (2009) obtained shifts in phoneme categorization resulting from external manipulation of the skin around the listener’s mouth in ways that would correspond to the deformations typical of producing these speech sounds (see also Yeung and Werker, 2013 for a similar demonstration with infants). Recently, Mochida et al. (2013) found that the ability to categorize consonants can be influenced by the simultaneous silent production of these consonants. Typically, these studies are proffered as evidence for a direct role of speech motor processing in speech perception. Independent of this proposed motor basis of perception, others have suggested the existence of a special speech or phonetic mode of perception based on evidence of neural and behavioral responses to the same stimuli being modulated by whether or not the listener believes the signal to be speech or non-speech (e.g., Tomiak et al., 1987; Vroomen and Baart, 2009; Stekelenburg and Vroomen, 2012).

When members of a series of synthesized stop consonants varying acoustically in F3 characteristics and varying perceptually from /da/ to /ga/ are preceded by /al/, subjects report hearing more /ga/ syllables relative to when each member is preceded by /ar/ (Mann, 1980). It has been suggested that this result demonstrates the existence of a mechanism that compensates for coarticulation via tacit knowledge of articulatory dynamics and constraints, or through perceptual recovery of vocal-tract dynamics. The present study was designed to assess the degree to which these perceptual effects are specific to qualities of human articulatory sources. In three experiments, series of consonant-vowel (CV) stimuli varying in F3-onset frequency (/da/-/ga/) were preceded by speech versions or nonspeech analogues of /al/ and /ar/. The effect of liquid identity on stop consonant labeling remained when the preceding VC was produced by a female speaker and the CV syllable was modeled after a male speaker's productions. Labeling boundaries also shifted when the CV was preceded by a sine wave glide modeled after F3 characteristics of /al/ and /ar/. Identifications shifted even when the preceding sine wave was of constant frequency equal to the offset frequency of F3 from a natural production. These results suggest an explanation in terms of general auditory processes as opposed to recovery of or knowledge of specific articulatory dynamics.

Bilinguals perceptually accommodate speech variation across languages, but to what extent this flexibility depends on bilingual experience is uncertain. One account suggests that bilingual experience promotes language-specific processing modes, implying that bilinguals can switch as appropriate between the different phonetic systems of the languages they speak. Another account suggests that bilinguals rapidly recalibrate to the unique acoustic properties of each language following language-general processes common to monolinguals. Challenging this latter account, the present results show that Spanish-English bilinguals with exposure to both languages from early childhood, but not English monolinguals, shift perception as appropriate across acoustically controlled English and Spanish contexts. Early bilingual experience appears to promote language-specific phonetic systems.

When presented a series of /dVd/ syllables varying perceptually from /ded/ to /d■d/, listeners identify the vowel sound as /■/ more often than when the vowels are presented alone as steady states. Conversely, /bVb/ series lead to more /e/ identifications. This pattern of responses appears to demonstrate a compensation for assimilatory effects of coarticulation or vowel ‘‘undershoot.’’ Experiments will be presented which test the specificity of this perceptual process. Two ten‐step (/bVb/ and /dVd/) series of 100‐ms /CVC/ syllables varying in F2 midpoint frequency (1260–1710 Hz) were synthesized. Nonspeech analogs were created by appending 70‐ms sine‐wave glides, which followed a similar trajectory to F2 in the speech stimuli, to 60‐ms steady‐state vowels varying in F2 frequency. A second set of nonspeech series was created by appending constant‐frequency sine‐wave tones to the vowel stimuli. The frequency of these tones were set at the F2 starting frequencies for the speech stimuli. These nonspeech contexts had effects on vowel identification that were analogous to those for the speech contexts. Lower frequency glides and tones (modeling /bVb/F2) led to more /e/ (higher F2) identifications with the complementary pattern for higher frequency glides and tones. [Work supported by NIDCD and NSF.]

Kluender, Lotto, and Jenison [J. Acoust. Soc. Am. 97, 2552–2567 (1995)] reported that overall stimulus amplitude can affect perception of the voicing contrast in syllable‐initial stops. Their results supported an hypothesis that a shift in the temporal pattern of neural firing from frequencies near F2 and F3 to F1 and f0 could signal voicelessness. The results of the current study undermine this ‘‘synchrony capture hypothesis.’’ The effect of amplitude (increased voiceless identifications with higher amplitude) maintains when there is no cutback in F1 during the quasiperiodic portion of the syllable and when stimuli are high‐pass filtered above the frequency of F1. In a further test of the hypothesis, two ten‐step series (/ba/–/pa/ and /ga/–/ka/) were created which maintained period voicing throughout the syllable (with F1 cutback signaling voicelessness). The energy just below the frequency of F2 and the energy above F1 were presented dichotically. Thus, at the periphery, there was no competition between frequencies near F2 and lower frequencies and, as a result, no chance for a change in neural temporal patterns. Subjects continued to label voicelessness as a function of overall amplitude. Alternative models of the encoding of voicelessness will be considered. [Work supported by NIDCD and NSF.]

In response to stop consonants with longer F1-cutback duration, the dominant synchronization of mid- and high-CF chinchilla auditory-nerve fibers changes from frequencies near F2 to frequencies near F1 at onset of voicing [D. G. Sinex and L. P. McDonald, J. Acoust. Soc. Am. 85, 1995-2004 (1989)]. If this change in neural synchronization is perceptually relevant for human listeners, then it may be predicted that changes in stimulus intensity and changes in the frequency difference between lower (F1) and higher (F2/F3) stimulus components should both affect perception of voicing. In a series of experiments, multiple continua of synthesized CVs varying in F1 cutback of the consonantal portion were played to listeners at levels ranging from 40 to 80 dB SPL. Across experiments, the frequency difference between F1 and F2 was manipulated by changing the onset frequency of F1 or F2. Subjects labeled more initial stops as voiceless as a function of increasing stimulus level and of decreasing frequency difference between F1 and F2. There was also an interaction between stimulus intensity and the frequency difference between F1 and F2 such that the effect of intensity was greater for smaller differences. These effects were reliable across a number of synthetic F1-cutback series, and the effect of intensity extended to a digitally edited series of hybrid CVs in which F1-cutback was varied by cross splicing naturally produced /da/ and /ta/. The effect of overall stimulus intensity was not affected by amplitude of prevocalic aspiration energy or by the presence or absence of release bursts. The results provide evidence for the perceptual significance of synchrony encoding of voicing for stop consonants.

Voices have unique acoustic signatures, contributing to the acoustic variability listeners must contend with in perceiving speech, and it has long been proposed that listeners normalize speech perception to information extracted from a talker’s speech. Initial attempts to explain talker normalization relied on extraction of articulatory referents, but recent studies of context-dependent auditory perception suggest that general auditory referents such as the long-term average spectrum (LTAS) of a talker’s speech similarly affect speech perception. The present study aimed to differentiate the contributions of articulatory/linguistic versus auditory referents for context-driven talker normalization effects and, more specifically, to identify the specific constraints under which such contexts impact speech perception. Synthesized sentences manipulated to sound like different talkers influenced categorization of a subsequent speech target only when differences in the sentences’ LTAS were in the frequency range of the acoustic cues relevant for the target phonemic contrast. This effect was true both for speech targets preceded by spoken sentence contexts and for targets preceded by non-speech tone sequences that were LTAS-matched to the spoken sentence contexts. Specific LTAS characteristics, rather than perceived talker, predicted the results suggesting that general auditory mechanisms play an important role in effects considered to be instances of perceptual talker normalization.

Speech is commonly claimed to relate to mirror neurons because of the alluring surface analogy of mirror neurons to the Motor Theory of speech perception, which posits that perception and production draw upon common motor-articulatory representations. We argue that the analogy fails and highlight examples of systems-level developmental approaches that have been more fruitful in revealing perception–production associations.

Speech perception (SP) most commonly refers to the perceptual mapping from the highly variable acoustic speech signal to a linguistic representation, whether it be phonemes, diphones, syllables, or words. This is an example of categorization, in that potentially discriminable speech sounds are assigned to functionally equivalent classes. In this tutorial, we present some of the main challenges to our understanding of the categorization of speech sounds and the conceptualization of SP that has resulted from these challenges. We focus here on issues and experiments that define open research questions relevant to phoneme categorization, arguing that SP is best understood as perceptual categorization, a position that places SP in direct contact with research from other areas of perception and cognition.

In a previous paper, Lotto et al. [J. Acoust. Soc. Am. 103, 3648–3655 (1998)] claimed that experiments investigating a perceptual magnet effect (PME) failed to demonstrate a novel effect of goodness judgments on speech sound discrimination due to a confound in the procedure. New analyses of these data and a review of the recent literature fail once again to support the existence of PME.

The discovery of mirror neurons, a class of neurons that respond when a monkey performs an action and also when the monkey observes others producing the same action, has promoted a renaissance for the Motor Theory (MT) of speech perception. This is because mirror neurons seem to accomplish the same kind of one to one mapping between perception and action that MT theorizes to be the basis of human speech communication. However, this seeming correspondence is superficial, and there are theoretical and empirical reasons to temper enthusiasm about the explanatory role mirror neurons might have for speech perception. In fact, rather than providing support for MT, mirror neurons are actually inconsistent with the central tenets of MT.

Although the main goal of our paper [1] was to argue against mirror neurons as a possible instantiation of the Motor Theory of speech, we also presented evidence in support for an alternative auditory theory of speech perception. That is, we promoted a model as in Figure 1a and against that represented in Figure 1b. Wilson [2] does not dispute this central position. Instead he argues that speech production regions could have a top-down influence on perception. We agree wholeheartedly and would add that speech production systems are not the only source of top-down information.

On the basis of a review of the literature and three new experiments, Fowler (2006) concludes that a contrast account for phonetic context effects is not tenable and is inferior to a gestural account. We believe that this conclusion is premature and that it is based on a restricted set of assumptions about a general perceptual account. Here, we briefly address the criticisms of Fowler (2006), with the intent of clarifying what a general auditory and learning approach to speech perception entails.

Fowler, Brown, and Mann (2000) have reported a visually moderated phonetic context effect in which a video disambiguates an acoustically ambiguous precursor syllable, which, in turn, influences perception of a subsequent syllable. In the present experiments, we explored this finding and the claims that stem from it. Experiment 1 failed to replicate Fowler et al. with novel materials modeled after the original study, but Experiment 2 successfully replicated the effect, using Fowler et al.'s stimulus materials. This discrepancy was investigated in Experiments 3 and 4, which demonstrate that variation in visual information concurrent with the test syllable is sufficient to account for the original results. Fowler et al.'s visually moderated phonetic context effect appears to have been a demonstration of audiovisual interaction between concurrent stimuli, and not an effect whereby preceding visual information elicits changes in the perception of subsequent speech sounds.

Behavioral experiments with infants, adults, and nonhuman animals converge with neurophysiological findings to suggest that there is a discontinuity in auditory processing of stimulus components differing in onset time by about 20 ms. This discontinuity has been implicated as a basis for boundaries between speech categories distinguished by voice onset time (VOT). Here, it is investigated how this discontinuity interacts with the learning of novel perceptual categories. Adult listeners were trained to categorize nonspeech stimuli that mimicked certain temporal properties of VOT stimuli. One group of listeners learned categories with a boundary coincident with the perceptual discontinuity. Another group learned categories defined such that the perceptual discontinuity fell within a category. Listeners in the latter group required significantly more experience to reach criterion categorization performance. Evidence of interactions between the perceptual discontinuity and the learned categories extended to generalization tests as well. It has been hypothesized that languages make use of perceptual discontinuities to promote distinctiveness among sounds within a language inventory. The present data suggest that discontinuities interact with category learning. As such, ‘‘learnability’’ may play a predictive role in selection of language sound inventories.

Listeners were trained to distinguish two novel classes of speech sounds differing in both Voice Onset Time (VOT) and fundamental frequency at vowel onset (f0). One group was shown Korean orthography during the training period (“symbols” group) and the other English orthography (“letters” group). During a subsequent test phase, listeners classified sounds with mismatched VOT and f0. The two groups relied on different cues to categorize the contrast: those exposed to symbols used f0, while those exposed to letters used VOT. A second experiment employed the same paradigm, but the two dimensions defining the contrast were closure duration (instead of f0) and VOT. In this more difficult experiment, successful listeners in the “letters” group again classified the hybrid stimuli based on VOT, while the single listener in the “symbols” group who passed the learning criterion used closure duration. In both experiments, subjects showed different categorization patterns based on orthography used in the presentation...

We present data quantifying the use of multiple acoustic dimensions in the perception and production of word-initial stops in Spanish and English in bilinguals and monolinguals, with a focus on the stability of individuals’ cue weighting strategies across languages and modalities. Early Spanish-English bilinguals who use both languages on a regular basis, along with control groups of monolingual Spanish and English speakers, categorized stop-initial CV syllables covarying in Voice Onset Time (VOT), fundamental frequency at vowel onset (f0), first formant onset frequency (F1), and stop closure duration. Individual perceptual cue weights were calculated via logistic regression, and these weights were compared with the same speakers’ use of the corresponding acoustic dimensions in their productions of the stop contrast. Preliminary results suggest that bilingual listeners’ perceptual cue weighting strategies correspond across Spanish and English; that is, individuals who weight a given cue more heavily than average in English also weight that cue heavily in Spanish. However, in line with previous work, correspondences between a given individual's use of the acoustic dimensions across perception and production are more elusive.

For stimuli modeling stop consonants varying in the acoustic correlates of voice onset time (VOT), human listeners are more likely to perceive stimuli with lower f0's as voiced consonants--a pattern of perception that follows regularities in English speech production. The present study examines the basis of this observation. One hypothesis is that lower f0's enhance perception of voiced stops by virtue of perceptual interactions that arise from the operating characteristics of the auditory system. A second hypothesis is that this perceptual pattern develops as a result of experience with f0-voicing covariation. In a test of these hypotheses, Japanese quail learned to respond to stimuli drawn from a series varying in VOT through training with one of three patterns of f0-voicing covariation. Voicing and f0 varied in the natural pattern (shorter VOT, lower f0), in an inverse pattern (shorter VOT, higher f0), or in a random pattern (no f0-voicing covariation). Birds trained with stimuli that had no f0-voicing covariation exhibited no effect of f0 on response to novel stimuli varying in VOT. For the other groups, birds' responses followed the experienced pattern of covariation. These results suggest f0 does not exert an obligatory influence on categorization of consonants as [VOICE] and emphasize the learnability of covariation among acoustic characteristics of speech.

In recent years there has been a great deal of interest in demonstrations of the so-called “Perceptual-Magnet Effect” (PME). In these studies, AX-discrimination tasks purportedly reveal that discriminability of speech sounds from a single category varies with judged phonetic “goodness” of the sounds. However, one possible confound is that category membership is determined by identification of sounds in isolation, whereas, discrimination tasks include pairs of stimuli. In the first experiment of the current study, identifications and goodness judgments were obtained for vowels (/i/–/e/) presented in pairs. A substantial shift in phonetic identity was evidenced with changes in the context vowel. In a second experiment, listeners participated in an AX-discrimination task with the vowel pairs from the first experiment. Using the contextual identification functions from the first experiment, predictions of discriminability were calculated using the classic tenets of Categorical Perception. Obtained discriminability functions were well accounted for by predictions from identification. There was no additional unexplained variance that required the proposal of “perceptual magnets.” These results suggest that PME may be nothing more than further demonstration that general discriminability is greater for cross-category stimulus pairs than for within-category pairs.

When members of a series of synthesized stop consonants varying in third-formant (F3) characteristics and varying perceptually from /da/ to /ga/ are preceded by /al/, human listeners report hearing more /ga/ syllables than when the members of the series are preceded by /ar/. It has been suggested that this shift in identification is the result of specialized processes that compensate for acoustic consequences of coarticulation. To test the species-specificity of this perceptual phenomenon, data were collected from nonhuman animals in a syllable "labeling" task. Four Japanese quail (Coturnix coturnix japonica) were trained to peck a key differentially to identify clear /da/ and /ga/ exemplars. After training, ambiguous members of a /da/–/ga/ series were presented in the context of /al/ and /ar/ syllables. Pecking performance demonstrated a shift which coincided with data from humans. These results suggest that processes underlying "perceptual compensation for coarticulation" are species-general. In addition, the pattern of response behavior expressed is rather common across perceptual systems.

Across a variety of languages, phonation type and vocal-tract shape systematically covary in vowel production. Breathy phonation tends to accompany vowels produced with a raised tongue body and/or advanced tongue root. A potential explanation for this regularity, based on a hypothesized interaction between the acoustic effects of vocal-tract shape and phonation type, is evaluated. It is suggested that increased spectral tilt and first-harmonic amplitude resulting from breathy phonation interact with the lower-frequency first formant resulting from a raised tongue body to produce a perceptually ‘higher’ vowel. To test this hypothesis, breathy and modal versions of vowel series modelled after male and female productions of English vowel pairs /i/ and /i/, /u/ and /ω/, and /λ/ and /a/ were synthesized. Results indicate that for most cases, breathy voice quality led to more tokens being identified as the higher vowel (i.e. /i/, /u/, /ÊŒ/). In addition, the effect of voice quality is greater for vowels modelled after female productions. These results are consistent with a hypothesized perceptual explanation for the covariation of phonation type and tongue-root advancement in West African languages. The findings may also be relevant to gender differences in phonation type.

From previous studies it is known that normal‐hearing (NH) listeners have the ability to compensate for the acoustic variability present in speech through context‐dependent perception of speech sounds. One question of practical and theoretical interest is whether listeners with cochlear implants (CI) also show context‐dependent speech perception. Because of the lack of spectral resolution in the input, the representation of speech for CI listeners may differ from NH listeners, which may interfere with perceptual compensation. In a test of this prediction, adult postlingually deafened CI listeners did not demonstrate the contrastive context effects elicited from NH listeners for either /da/–/ga/ targets and /al/–/ar/ contexts or V targets and /b—b/–/d—d/ contexts. In contrast, as predicted by the good temporal resolution of the CI signal, CI listeners showed normal effects of vowel length on preceding glide‐stop categorization. CI simulations with NH listeners were also performed for some of these context ...

Research in the field of speech perception has traditionally focused on the acoustic information or cues present in the frequency region below 5 kHz, thus ignoring high frequency energy (HFE). A recent series of studies, however, demonstrated that listeners could determine the mode of production (speech or singing) and further, could identify what was being spoken or sung from the HFE alone and with a speech-shaped masking noise in the lower frequencies. This begs the question as to what types of information listeners are extracting to guide their perception. The current study examined the ability of listeners to transcribe short semantically-unpredictable but syntactically-well-formed spoken phrases that were high-pass filtered at 5.6 kHz. Of particular interest was the ability of some listeners to correctly determine the placement of word boundaries even without the availability of low-frequency information. These findings add to a growing literature on the linguistically relevant information present in higher frequency regions. Results will be framed within current theories of acoustic signatures to lexical segmentation. [Work supported by NIH-NIDCD.]

This work investigates the production and perception of the English stop voicing contrast on multiple acoustic dimensions by native speakers of Seoul Korean. Subjects completed a production task as well as a forced-choice identification task on stimuli varying on three acoustic dimensions (aspiration duration, pitch, and closure duration) in both English and Korean. On average, native Korean listeners relied more on pitch than on aspiration duration to categorize the English stop voicing contrast (which native English listeners distinguish primarily by aspiration). However, individual categorization patterns differed considerably, with some listeners using only pitch, some using only aspiration, and most using both. In contrast, in production, aspiration duration was a better predictor of voicing category than pitch, although pitch was still a stronger predictor than previously found in native English productions. The heavier reliance on pitch by Korean listeners may be attributable to the greater importance of pitch in their native stop contrast; however, there does not appear to be a consistent, straightforward mapping of English sounds onto the Korean categories. Results will be discussed in the terms of the perception-production interface on the level of individual acoustic cues, as well as the influence of native language cue weights on non-native sound contrasts.

Listeners were randomly presented narrow-band filtered noise bursts that varied in filter center frequency from two overlapping, Gaussian-like distributions. Participants mapped these distributions of sounds onto creatures in a video game where they received visual and auditory feedback about their accuracy. Categorization boundaries for each participant were estimated using logistic regression and compared with the optimal boundary from an ideal observer model. The participants appeared to be able to establish near optimal boundaries rapidly and had a remarkable ability to shift these boundaries when the underlying distributions changed - even when these changes were not explicitly signaled. These results suggest that listeners maintain a rather detailed representation of distributional information that is continuously updated during the task. This interpretation is in line with the assumptions underlying many current models of perceptual (statistical) learning in speech perception. However, it is possib...

For more than fifty years, it has been known that listeners’ perception of a target speech sound may shift as a result of a change in speaker of a preceding carrier phrase. The predominant theories explaining this phenomenon suggest that the listener must be extracting information specific to the speaker - either generating speaker-specific acoustic-phonemic mapping or an estimate of the dimensions of the speaker’s vocal tract. To the extent that these processes derive representations that are specific to a speaker, one would not expect shifts in target perception when the apparent speaker remains unchanged. This prediction was explicitly tested by appending targets to different carrier phrases produced by the same speaker. Speaker characteristics were controlled by using an articulatory synthesizer that allows one to specify the source and dimensions of the vocal tract. Significant shifts in target perception were readily obtained, even when the speaker remained the same. These results suggest that these...

High-density electroencephalography (EEG) was used to evaluate cortical activity patterns during the auditory processing of speech presented at various levels of degradation in a sentence verification task. 25 healthy participants listened to true-false sentences produced with one of 3 channel levels (1, 6, 16), ranging from unintelligible, moderately intelligible, and highly intelligible. Behavioral data were collected via button press (reaction time and accuracy) for each sentence. The analysis of cortical activation patterns includes 1) the identification of independent components that account for variations of activity associated with degradation levels and 2) the examination of associated event-related potentials. Statistical analyses will be performed on individuals' cortical activity, in tandem with behavioral data. Preliminary results reveal differences in the timing and magnitude of frontal and temporal lobe activation that coincide with task difficulty. Results of the present investigation will ...

When F1‐onset frequency is lower, longer F1 cutback (VOT) is required for human listeners to perceive synthesized stop consonants as voiceless. K. R. Kluender [J. Acoust. Soc. Am. 90, 83–96 (1991)] found comparable effects of F1‐onset frequency on the ‘‘labeling’’ of stop consonants by Japanese quail (coturnix coturnix japonica) trained to distinguish stop consonants varying in F1 cutback. In that study, CVs were synthesized with naturallike rising F1 transitions, and endpoint training stimuli differed in the onset frequency of F1 because a longer cutback resulted in a higher F1 onset. In order to assess whether earlier results were due to auditory predispositions or due to animals having learned the natural covariance between F1 cutback and F1‐onset frequency, the present experiment was conducted with synthetic continua having either a relatively low (375 Hz) or high (750 Hz) constant‐frequency F1. Six birds were trained to respond differentially to endpoint stimuli from three series of synthesized /CV/s varying in duration of F1 cutback. Second and third formant transitions were appropriate for labial, alveolar, or velar stops. Despite the fact that there was no opportunity for animal subjects to use experienced covariation of F1‐onset frequency and F1 cutback, quail typically exhibited shorter labeling boundaries (more voiceless stops) for intermediate stimuli of the continua when F1 frequency was higher. Responses by human subjects listening to the same stimuli were also collected. Results lend support to the earlier conclusion that part or all of the effect of F1 onset frequency on perception of voicing may be adequately explained by general auditory processes. Implications concerning VOT variation for stop consonants at different places of articulation or preceding different vowels are discussed.

This study explores whether information obtained from the envelope modulation spectrum (EMS) can predict the type of intelligibility decrement experienced by listeners of dysarthric speech. Previously, Liss et al. [J. Speech Lang. Hear. Res. 53, 1246–1255 (2010)] demonstrated that spectralinformation obtained via EMS can classify individuals with different patterns of degraded speech into their appropriate clusters. Variables noted as significant in discriminating dysarthria types, such as relative energy above and below the region of 4 Hz, are of particular interest. While the analyzes showed variations of energy in certain octaves of the acoustic signal were critical for this analysis, it is unclear which perceptual components map onto these measures. Using performance measures that capture listeners’ strategies to understand speech at the segmental, suprasegmental, and phonetic levels (intelligibility, lexical boundary errors, and word substitutions), regressions will be performed to determine which information contained within the EMS metrics can account for the variability in listener performance at various levels. Ultimately, this will allow us to look at trends in the EMS output, identify the source of intelligibility decrement, and predict listener performance on outcome measures. Results will bear on models of connected speech perception as well as clinical practice.

Previous work has provided evidence that the presence/absence of carrier phrase effects on target speech sound categorization can be well predicted by comparing the long‐term average spectrum (LTAS) of the carrier phrase with the spectrum of the target. In this series of studies, we move beyond asking whether there is a significant effect or not to examining the relative size of these effects. Target series of minimal‐pair words varying in vowel were preceded by carrier phrases synthesized to simulate a talker with a large or short vocal tract. Shifts in vowel categorization percentage as a function of change in talker served as the variable of interest. Results indicate that manipulations of the perception of the carrier as speech (by presenting forward or backwards), the LTAS of the carrier (by gating the duration of the carrier presented), and the local information in the carrier (by preserving or not the part of the carrier immediately preceding the target) affected the size of the resulting shifts. Of particular interest, the LTAS has an affect above and beyond the spectrum nearest to the target and the carriers perceived as speech resulted in larger shifts even when LTAS was held constant. [Work Supported by NIH‐NIDCD].

Traditionally, acoustical energy above 5000 Hz in voice and speech has received little attention from the scientific community. Some recent studies have explored the role of this high‐frequency energy (HFE) in qualitative percepts of speech and music. To determine what other perceptual information is extractable from this frequency range, listeners were presented with tokens containing only HFE from samples of singing and speech (i.e., singing and speech high‐pass filtered at approximately 5.7 kHz). Results showed that listeners could successfully discriminate gender and mode of production (speech versus singing) given only acoustical energy above 5 kHz. Additionally, listeners successfully identified the song being sung and the words being spoken. The implication is that HFE potentially plays a more significant role in perception of singing and speech than that suggested by the current understanding. [Work supported by the NIH‐NIDCD.]

Ladefoged and Broadbent [J. Acoust. Soc. Am. 29, 98–104 (1957)] demonstrated that listeners will shift their categorization of a target vowel as a function of acoustic characteristics of a preceding carrier phrase. These results have been interpreted as an example of perceptual normalization for variability resulting from differences in talker anatomy. The present study examined whether listeners would normalize for acoustic variability resulting from differences in speaking style within a single talker. Two vowel series were synthesized that varied between central and peripheral vowels (the vowels in “beat”‐“bit” and “bod”‐“bud”). Each member of the series was appended to one of four carrier phrases that were spoken in either a “clear” or “reduced” speech style. Participants categorized vowels in these eight contexts. A reliable shift in categorization as a function of speaking style was obtained for three of four phrase sets. This demonstrates that phrase context effects can be obtained with a single ta...

Speech production disorders arise from a wide variety of anatomical defects, neurological injury, and disease. Depending on the etiology, the speech manifestations may be quite regularized—in the same way that a foreign accent presents consistently—or highly variable with unpredictable speech interruption and degradation. Indeed, even within an individual speaker, one will find both relatively consistent and variable aspects of speech abnormality. A growing body of literature shows that listeners enjoy intelligibility gains with just brief auditory exposure to disordered speech that is accompanied by lexical feedback, and with repeated unsupervised exposures. These benefits have been shown to be both talker‐specific and applicable to groups of people who presumably share relevant acoustic‐perceptual speech features. While many of these studies have been designed with an eye toward clinical and communicative implications, there is much to be learned about the mechanisms underlying these perceptual improvements with naturally impoverished speech. The purpose of this presentation is to describe the use of clinical populations as a testing ground for hypotheses of listener learning and adaptation. Speech production disorders particularly lend themselves to the study of episodic memory, rhythmic expectancy, and talker‐specific versus talker‐general effects. [Work supported by NIDCD, NIH.]

Recent work has indicated that the perception of speech sounds shifts as a function of preceding and following context and that these shifts are due in part to the particular spectral makeup of the context sounds [Holt et al., J. Acoust. Soc. Am. 108, 710–722 (2000)]. Aravamudhan and Lotto [J. Acoust. Soc. Am. 118, 1962–1963 (2005)] studied these context effects in listeners with cochlear implants (CI) and the results demonstrated absent or abnormal context‐dependent speech perception. The lack of normal context effects in CI users may have practical implications for situations in which there is substantial coarticulation (e.g., nonlaboratory speech) or talker variability (e.g., switching between multiple speakers). Since the representation of speech in CI listeners differs from NH listeners, the current study was designed to investigate the effects of processing normal signals through a CI processor with NH listeners. In particular, we investigated how the spectral resolution of implant input could limit...

The categorization of speech sounds into phonetic units has been characterized as involving the differential weighting of perceptual cues. Cue weighting has been often explicitly or implicitly associated with the construct of selective attention. We will present data from speech and non‐speech categorization studies that attempt to illuminate the factors that influence relative weighting of perceptual dimensions. Of particular interest is the role of variability across the different auditory dimensions. The results of these experiments will be related to work on cue weighting in other psychophysical tasks and the usefulness of the attention construct will be explored. [Work supported by NSF BCS0345773].

Several experiments were performed to examine the ability of humans to categorize sounds as a function of training distribution characteristics. Participants were presented non‐speech sounds randomly sampled from two overlapping distributions. The sounds consisted of 25 narrow‐band noise bursts varying in center frequency from 1000–1360 Hz. Two conditions were created by varying the ratio of stimuli in each category (i.e., prior probabilities of each category), resulting in different ideal boundaries (maximizing accuracy). Participants were asked to categorize the sounds as either A or B and feedback was provided. In one experiment, prior probabilities were altered mid‐session without alerting the subjects. Performance was tracked by plotting identification functions and noting boundary placement for each individual block. After only six blocks of training (∼35 min), most subjects had established optimal or near‐optimal boundaries. Identification function slopes were calculated and found to be steeper than training distribution slopes; suggesting that listeners established criterion‐like boundaries as opposed to performing probability matching. The fact that listeners adjusted their responses in accordance to distribution changes within relatively short periods of time demonstrates the perceptual systems effectiveness at optimizing categorization based on distribution characteristics. [Work supported by NSF and NIDCD.]

The present study was designed to investigate the effects of long‐term linguistic experience on the perception of non‐speech sounds in English and Spanish speakers. Research using tone‐onset‐time (TOT) stimuli, a type of non‐speech analogue of voice‐onset‐time (VOT) stimuli, has suggested that there is an underlying auditory basis for the perception of stop consonants based on a threshold for detecting onset asynchronies in the vicinity of +20 ms. For English listeners, stop consonant labeling boundaries are congruent with the positive auditory discontinuity, while Spanish speakers place their VOT labeling boundaries and discrimination peaks in the vicinity of 0 ms VOT. The present study addresses the question of whether long‐term linguistic experience with different VOT categories affects the perception of non‐speech stimuli that are analogous in their acoustic timing characteristics. A series of synthetic VOT stimuli and TOT stimuli were created for this study. Using language appropriate labeling and ABX discrimination tasks, labeling boundaries (VOT) and discrimination peaks (VOT and TOT) are assessed for 24 monolingual English speakers and 24 monolingual Spanish speakers. The interplay between language experience and auditory biases are discussed. [Work supported by NIDCD.]

Perceptual overshoot (PO), a phenomenon in which the boundary for perceived vowel categories shifts as a result of preceding formant transitions, has been demonstrated previously with synthetic vowels in CV contexts in normal‐hearing individuals. In one of the previous studies by the author, the same phenomenon was tested with sinewave analogs that mimicked the synthetic vowels. The results demonstrated that PO could be elicited for sinewave analogs after training on categorization of sinewave steady states. These findings suggest that PO may be partly mediated by general processes in the auditory system. In the current study, subjects with cochlear implants were presented with synthetic vowel and sinewave continua with and without transitions. It was predicted that PO would be greatly diminished or absent for this population because of the degraded nature of the spectral input. Implications of the results for theories of speech perception will be presented.

The ability to integrate and weight information across dimensions is central to perception. The present experiments investigate this issue by training participants to categorize sounds drawn from two input distributions in a two‐dimensional acoustic space defined by frequency‐modulated sine waves center frequency (CF) and modulation frequency (MF). These dimensions were psychophysically matched to be equally discriminable and, in the first experiment, were equally informative for accurate categorization. Nevertheless, listeners’ category responses reflected a bias for use of CF. This bias was moderated when the informativeness of CF was decreased by shifting distributions to create more overlap in CF. A reversal of weighting (MF over CF) was obtained when distribution variance was increased for CF. These results demonstrate that even when equally informative and discriminable, acoustic cues are not necessarily equally weighted in categorization; listeners exhibit biases when integrating multiple acoustic dimensions. Moreover, drastic changes in weighting strategies can be affected by changes in input distribution parameters. This methodology provides potential insights into acquisition of speech sound categories, particularly second language categories. One implication is that ineffective cue weighting strategies for phonetic categories may be alleviated by adding variance to noninformative dimensions in training stimuli. [Work supported by NIH.]

The idea that speech perception is shaped by the statistical structure of the input is gaining wide enthusiasm and growing empirical support. Nonetheless, statistics and statistical learning are broad terms with many possible interpretations and, perhaps, many potential underlying mechanisms. In order to define the role of statistics in speech perception mechanistically, we will need to more precisely define the statistics of statistical learning and examine similarities and differences across subgroups. In this talk, we examine learning of four types of information: (1) acoustic variance that is defining for contrastive categories, (2) the correlation between acoustic attributes or linguistic features, (3) the probability or frequency of events or a series of events, (4) the shape of input distributions. We present representative data from online speech perception and speech development and discuss inter‐relationships among the subgroups. [Work supported by NSF, NIH and the James S. McDonnell Foundation.]

Behavioral experiments with infants, adults and nonhuman animals converge with neurophysiological findings to suggest that there is a discontinuity in auditory processing of stimulus components differing in onset time by about 20 ms. This discontinuity has been implicated as a basis for boundaries between speech categories distinguished by VOT. Here, we investigate how this discontinuity interacts with the learning of novel perceptual categories. Adult listeners were trained to categorize a nonspeech acoustic cue that mimics the temporal distinction of VOT. One group of listeners learned categories with a boundary coincident with the perceptual discontinuity. Another group learned categories defined such that the perceptual discontinuity fell within a category. Listeners in the latter group required significantly more experience to reach criterion categorization performance. The evidence of interactions between the perceptual discontinuity and the learned categories extended to generalization tests as well. It has been hypothesized that languages make use of perceptual discontinuities to promote perceptual distinctiveness among sounds within a language inventory. The present data suggest that these influences interact with category learning. As such, learnability may play a predictive role in selection of language sound inventories. Moreover, it may be possible to observe predictable learning effects in infant speech perception.