Perceptual Organization Of Speech Research Articles

A test of linguistic influences in the perceptual organization of speech.

Research in speech perception has explored how knowledge of a language influences phonetic perception. The current study investigated whether such linguistic influences extend to the perceptual (sequential) organization of speech. Listeners heard sinewave analogs of word pairs (e.g., loose seam, which contains a single [s] frication but is perceived as two /s/ phonemes) cycle continuously, which causes the stimulus to split apart into foreground and background percepts. They had to identify the foreground percept when the stimuli were heard as nonspeech and then again when heard as speech. Of interest was how grouping changed across listening condition when [s] was heard as speech or as a hiss. Although the section of the signal that was identified as the foreground differed little across listening condition, a strong bias to perceive [s] as forming the onset of the foreground was observed in the speech condition (Experiment 1). This effect was reduced in Experiment 2 by increasing the stimulus repetition rate. Findings suggest that the sequential organization of speech arises from the interaction of auditory and linguistic processes, with the former constraining the latter.

Age effects on perceptual organization of speech: Contributions of glimpsing, phonemic restoration, and speech segregation

In realistic listening environments, speech perception requires grouping together audible fragments of speech, filling in missing information, and segregating the glimpsed target from the background. The purpose of this study was to determine the extent to which age-related difficulties with these tasks can be explained by declines in glimpsing, phonemic restoration, and/or speech segregation. Younger and older adults with normal hearing listened to sentences interrupted with silence or envelope-modulated noise, presented either in quiet or with a competing talker. Older adults were poorer than younger adults at recognizing keywords based on short glimpses but benefited more when envelope-modulated noise filled silent intervals. Recognition declined with a competing talker but this effect did not interact with age. Results of cognitive tasks indicated that faster processing speed and better visual-linguistic closure were predictive of better speech understanding. Taken together, these results suggest that age-related declines in speech recognition may be partially explained by difficulty grouping short glimpses of speech into a coherent message.

Neural Correlates of Speech Segregation Based on Formant Frequencies of Adjacent Vowels

The neural substrates by which speech sounds are perceptually segregated into distinct streams are poorly understood. Here, we recorded high-density scalp event-related potentials (ERPs) while participants were presented with a cyclic pattern of three vowel sounds (/ee/-/ae/-/ee/). Each trial consisted of an adaptation sequence, which could have either a small, intermediate, or large difference in first formant (Δf1) as well as a test sequence, in which Δf1 was always intermediate. For the adaptation sequence, participants tended to hear two streams (“streaming”) when Δf1 was intermediate or large compared to when it was small. For the test sequence, in which Δf1 was always intermediate, the pattern was usually reversed, with participants hearing a single stream with increasing Δf1 in the adaptation sequences. During the adaptation sequence, Δf1-related brain activity was found between 100–250 ms after the /ae/ vowel over fronto-central and left temporal areas, consistent with generation in auditory cortex. For the test sequence, prior stimulus modulated ERP amplitude between 20–150 ms over left fronto-central scalp region. Our results demonstrate that the proximity of formants between adjacent vowels is an important factor in the perceptual organization of speech, and reveal a widely distributed neural network supporting perceptual grouping of speech sounds.

Constraints on Sensitivity to Auditory Modulation in the Perceptual Organization of Speech

Background/Study Context: The perception of speech requires the integration of sensory details from a rapidly fading trace of a time-varying spectrum. This effortful cognitive function has been difficult to assess. New tests measuring intelligibility of sine-wave replicas of speech provided an assay of this critical function in normal-hearing young adults.Methods: Four time-varying sinusoids replicated the frequency and amplitude variation of the natural resonances of spoken sentences. The temporal tolerance of perceptual integration of speech was measured by determining the effect on intelligibility of desynchronizing a single sine-wave component in each sentence. This method was applied in tests in which the sentences were temporally compressed or expanded over a 40% range.Results: Desynchrony was harmful to perceptual integration over a narrow temporal range, indicating that modulation sensitivity is keyed to a rate of 20 Hz. No effect of variation in speech rate was observed on the intelligibility measure, whether rate was accelerated or decelerated relative to the natural rate.Conclusion: Performance measures of desynchrony tolerance did not vary when speech rate was accelerated or decelerated, revealing constraints on integration that are arguably primitive, sensory, auditory, and fixed. Because these are not adaptable, they limit the potential for perceptual learning in this aspect of perceptual organization. Implications for describing the elderly listener are noted.

The verbal transformation effect and the perceptual organization of speech: Influence of formant transitions and F0-contour continuity

This study explored the role of formant transitions and F0-contour continuity in binding together speech sounds into a coherent stream. Listening to a repeating recorded word produces verbal transformations to different forms; stream segregation contributes to this effect and so it can be used to measure changes in perceptual coherence. In experiment 1, monosyllables with strong formant transitions between the initial consonant and following vowel were monotonized; each monosyllable was paired with a weak-transitions counterpart. Further stimuli were derived by replacing the consonant-vowel transitions with samples from adjacent steady portions. Each stimulus was concatenated into a 3-min-long sequence. Listeners only reported more forms in the transitions-removed condition for strong-transitions words, for which formant-frequency discontinuities were substantial. In experiment 2, the F0 contour of all-voiced monosyllables was shaped to follow a rising or falling pattern, spanning one octave. Consecutive tokens either had the same contour, giving an abrupt F0 change between each token, or alternated, giving a continuous contour. Discontinuous sequences caused more transformations and forms, and shorter times to the first transformation. Overall, these findings support the notion that continuity cues provided by formant transitions and the F0 contour play an important role in maintaining the perceptual coherence of speech.

Modulation sensitivity in the perceptual organization of speech

In a spoken utterance, a talker expresses linguistic constituents in serial order. A listener resolves these linguistic properties in the rapidly fading auditory sample. Classic measures agree that auditory integration occurs at a fine temporal grain. In contrast, recent studies have proposed that sensory integration of speech occurs at a coarser grain, approximate to the syllable, on the basis of indirect and relatively insensitive perceptual measures. Evidence from cognitive neuroscience and behavioral primatology has also been adduced to support the claim of sensory integration at the pace of syllables. In the present investigation, we used direct performance measures of integration, applying an acoustic technique to isolate the contribution of short-term acoustic properties to the assay of modulation sensitivity. In corroborating the classic finding of a fine temporal grain of integration, these functional measures can inform theory and speculation in accounts of speech perception.

Perceptuo-motor interactions in the perceptual organization of speech: evidence from the verbal transformation effect.

The verbal transformation effect (VTE) refers to perceptual switches while listening to a speech sound repeated rapidly and continuously. It is a specific case of perceptual multistability providing a rich paradigm for studying the processes underlying the perceptual organization of speech. While the VTE has been mainly considered as a purely auditory effect, this paper presents a review of recent behavioural and neuroimaging studies investigating the role of perceptuo-motor interactions in the effect. Behavioural data show that articulatory constraints and visual information from the speaker's articulatory gestures can influence verbal transformations. In line with these data, functional magnetic resonance imaging and intracranial electroencephalography studies demonstrate that articulatory-based representations play a key role in the emergence and the stabilization of speech percepts during a verbal transformation task. Overall, these results suggest that perceptuo (multisensory)-motor processes are involved in the perceptual organization of speech and the formation of speech perceptual objects.

Is desynchrony tolerance adaptable in the perceptual organization of speech?

Is desynchrony tolerance adaptable in the perceptual organization of speech?

Is desynchrony tolerance adaptable in the perceptual organization of speech?

Speech signal components that are desynchronized from the veridical temporal pattern lose intelligibility. In contrast, audiovisual presentations with large desynchrony in visible and audible speech streams are perceived without loss of integration. Under such conditions, the limit of desynchrony that permits audiovisual integration is also adaptable. A new project directly investigated the potential for adaptation to consistent desynchrony with unimodal auditory sine-wave speech. Listeners transcribed sentences that are highly intelligible, with veridical temporal properties. Desynchronized variants were created by leading or lagging the tone analog of the second formant relative to the rest of the tones composing the sentences, in 50-msec steps, ranging from 250-msec lead to 250-msec lag. In blocked trials, listeners only tolerated desynchronies <50 msec, and exhibited no gain in intelligibility to consistent desynchrony. Unimodal auditory and bimodal audiovisual forms of perceptual integration evidently exhibit different temporal characteristics, an indication of distinct perceptual functions.

Disruption by speech of serial short-term memory: The role of changing-state vowels

Serial short-term memory is markedly impaired by the presence of irrelevant speech so long as the successive tokens within the irrelevant speech are phonologically (or acoustically) dissimilar (Jones & Macken, 1995b). In two experiments in which consonant-vowel-consonant syllables were used as irrelevant speech tokens, we sought to evaluate the relative disruptive potency of changes in the final consonant only (Experiment 1), in the initial consonant, or in the vowel portion (Experiment 2) of each token. The results suggest that the vowel changes are the dominant source of disruption. This dominance may be explained, at least in part, by the role played by vowel sounds in the perceptual organization of speech and, in turn, the particular propensity for vowel changes to yield information about serial order. The results are consistent also with the view that the factors that promote order encoding in sound are also the ones that promote disruption.

The effects of duration changes on the perception of vowel sequences

Previous studies have shown that listeners exposed to a repeated sequence of steady-state vowels (of same duration and pitch) experience phonemic transformations, and report hearing words and phrases absent in the original stimulus. A previous study [M. H. Chalikia, R. Meyer, and R. Lindemann, 34th Psychon. Society Meet. (1993)] investigated the possible effects of variations in vowel duration. Duration variations ranged from 30 to 120 ms per vowel. Listeners successfully matched these stimuli to the verbal forms heard with vowels of equal duration and pitch, confirming the robust, stable nature of the verbal organizations. It was suggested that these organizations are based upon objective acoustic characteristics, and the stimulus manipulations were probably perceived as prosodic variations. In this study a broader variation in duration was employed (10–300 ms), in an attempt to examine listeners’ limitations in performing the matching task. Six base-line sequences of six 80-ms vowels (at 100 Hz), followed by a 300-ms silent gap, were used. Four variations of these were created by randomly changing the duration of individual vowels within a sequence. Most listeners were not able to perform the task. Implications concerning the perceptual organization of speech will be discussed.

On the perceptual organization of speech.

A general account of auditory perceptual organization has developed in the past 2 decades. It relies on primitive devices akin to the Gestalt principles of organization to assign sensory elements to probable groupings and invokes secondary schematic processes to confirm or to repair the possible organization. Although this conceptualization is intended to apply universally, the variety and arrangement of acoustic constituents of speech violate Gestalt principles at numerous junctures, cohering perceptually, nonetheless. The authors report 3 experiments on organization in phonetic perception, using sine wave synthesis to evade the Gestalt rules and the schematic processes alike. These findings falsify a general auditory account, showing that phonetic perceptual organization is achieved by specific sensitivity to the acoustic modulations characteristic of speech signals.

On the perceptual organization of speech.

On the perceptual organization of speech.

Perceptual organization of speech signals: Clues from studies of sinewave replicas of utterances

The perceptual organization of speech is a challenge for accounts proposing a two-stage model in which primitive auditory grouping is followed by schematic secondary processes. This difficulty stems from the diversity of acoustic constituents of speech signals, which is attributable in turn to the mechanics of vocal sound production. Primitive mechanisms that rely on similarity principles to group like elements therefore fail to parse the sound stream isomorphically to the sound sources. The insufficiency of primitive grouping mechanisms for organizing speech signals is often admitted, and knowledge-based latterly occurring processes are often invoked to explain the self-evident perceptual coherence of utterances. Studies with sinewave replicas of words and sentences show that phonetic perception occurs in conditions that thwart the application of primitive grouping mechanisms as they are presently understood. Psychophysical tests with sinewave words suggest that the perceptual organization of speech is distinct from other auditory organization. Because classic evidence and arguments discourage schema-based conceptualizations of phonetic processes, the two- stage model of organization appears to be implausible for speech. Perceptual organization of speech can better be rationalized by a phonetically specific facility that organizes and analyzes utterances. [Research supported by NIDCD and NICHD.]

Phonetic coherence in duplex perception: effects of acoustic differences and lexical status.

A modified version of duplex perception was used to investigate the nature of perceptual organization of speech. Ss were asked to identify stimuli in which a third-formant transition was presented to 1 ear and a full syllable (base) was presented to the other ear. Phonetic integration occurred even when the spectral composition or onset frequency of the isolated transition was varied relative to the base. However, when onset asynchronies were added to spectral differences, the isolated transition ceased to contribute to the syllable percept. Lexical status of the eventual phonetic percepts also influenced the phonetic integration of acoustic components into syllable percepts. These results suggest that combinations of low-level acoustic and phonetic differences between components and higher level lexical information interact to influence the grouping of acoustic components into phonetic percepts.

Phonemic Transformations: Mapping the Illusory Organization of Steady-State Vowel Sequences

Previous research has shown that listeners presented with repeated sequences of brief steady-state vowels (30–100 msec) experience phonemic transformations (that is, illusory changes in the identity of the constituent speech sounds) and report hearing verbal forms consisting of one or more syllables rather than a succession of vowels. Often the signal is split perceptually into two simultaneous organizations differing in both timbre and phonemic content. The present studies employed sequences of eight 80-msec vowels and mapped the perceptual phonemes to acoustic phones by terminating the repeated sequence at predetermined positions and determining the last speech sound heard in the perceived verbal organization (Experiments 1 and 2). When two simultaneous organizations were heard, they were both mapped (Experiments 2 and 3). It was found that: (1) all listeners reported hearing a polysyllabic verbal organization together with either a noise-like non-linguistic residue or a second verbal organization; (2) the verbal forms heard not only followed the phonotactic rules of English, but also corresponded to syllables actually found in English; (3) when two simultaneous organizations were heard, the primary or more salient one was usually longer; (4) simultaneous organizations had different timbres. Implications concerning the perceptual organization of speech are discussed.

Mapping the organization of vowel sequences into words

Previous research [Warren et al., Percept. Psychophys. (in press)] has shown that when listeners hear recycled sequences of steady‐state vowels, they do not perceive them as a succession of vowels. Illusory phonemes are introduced and real or nonsense words are heard. Often the sequence of vowels is split perceptually in two simultaneous words differing in both quality and phonemic content. The present study employed sequences of eight 80‐ms vowels, and mapped the perceptual phonemes to acoustic phoneroes by terminating the repeated sequence at various positions and determining the last sound heard in the perceived word for each position. When two simultaneous words were heard, they both were mapped. Relations between the acoustic phonemes and the perceived phonemes will be described, and implications concerning the perceptual organization of speech will be discussed. [Work supported by NIH and AFOSR.]