Musical Sophistication and Speech Auditory-Motor Coupling: Easy Tests for Quick Answers

The human auditory system uses amplitude modulation to distinguish music from speech

Music and speech are complex and distinct auditory signals that are both foundational to the human experience. The mechanisms underpinning each domain are widely investigated. However, what perceptual mechanism transforms a sound into music or speech and how basic acoustic information is required to distinguish between them remain open questions. Here, we hypothesized that a sound's amplitude modulation (AM), an essential temporal acoustic feature driving the auditory system across processing levels, is critical for distinguishing music and speech. Specifically, in contrast to paradigms using naturalistic acoustic signals (that can be challenging to interpret), we used a noise-probing approach to untangle the auditory mechanism: If AM rate and regularity are critical for perceptually distinguishing music and speech, judging artificially noise-synthesized ambiguous audio signals should align with their AM parameters. Across 4 experiments (N = 335), signals with a higher peak AM frequency tend to be judged as speech, lower as music. Interestingly, this principle is consistently used by all listeners for speech judgments, but only by musically sophisticated listeners for music. In addition, signals with more regular AM are judged as music over speech, and this feature is more critical for music judgment, regardless of musical sophistication. The data suggest that the auditory system can rely on a low-level acoustic property as basic as AM to distinguish music from speech, a simple principle that provokes both neurophysiological and evolutionary experiments and speculations.

Syllabic rhythm and prior linguistic knowledge interact with individual differences to modulate phonological statistical learning

Phonological statistical learning - our ability to extract meaningful regularities from spoken language - is considered critical in the early stages of language acquisition, in particular for helping to identify discrete words in continuous speech. Most phonological statistical learning studies use an experimental task introduced by Saffran et al. (1996), in which the syllables forming the words to be learned are presented continuously and isochronously. This raises the question of the extent to which this purportedly powerful learning mechanism is robust to the kinds of rhythmic variability that characterize natural speech. Here, we tested participants with arhythmic, semi-rhythmic, and isochronous speech during learning. In addition, we investigated how input rhythmicity interacts with two other factors previously shown to modulate learning: prior knowledge (syllable order plausibility with respect to participants' first language) and learners' speech auditory-motor synchronization ability. We show that words are extracted by all learners even when the speech input is completely arhythmic. Interestingly, high auditory-motor synchronization ability increases statistical learning when the speech input is temporally more predictable but only when prior knowledge can also be used. This suggests an additional mechanism for learning based on predictions not only about when but also about what upcoming speech will be.

Audiovisual integration in the McGurk effect is impervious to music training

The McGurk effect refers to an audiovisual speech illusion where the discrepant auditory and visual syllables produce a fused percept between the visual and auditory component. However, little is known about how individual differences contribute to the McGurk effect. Here, we examined whether music training experience-which involves audiovisual integration-can modulate the McGurk effect. Seventy-three participants completed the Goldsmiths Musical Sophistication Index (Gold-MSI) questionnaire to evaluate their music expertise on a continuous scale. Gold-MSI considers participants' daily-life exposure to music learning experiences (formal and informal), instead of merely classifying people into different groups according to how many years they have been trained in music. Participants were instructed to report, via a 3-alternative forced choice task, "what a person said": /Ba/, /Ga/ or /Da/. The experiment consisted of 96 audiovisual congruent trials and 96 audiovisual incongruent (McGurk) trials. We observed no significant correlations between the susceptibility of the McGurk effect and the different subscales of the Gold-MSI (active engagement, perceptual abilities, music training, singing abilities, emotion) or the general musical sophistication composite score. Together, these findings suggest that music training experience does not modulate audiovisual integration in speech as reflected by the McGurk effect.

Amplitude envelope onset characteristics modulate phase locking for speech auditory-motor synchronization

The spontaneous speech-to-speech synchronization (SSS) test has been shown to be an effective behavioral method to estimate cortical speech auditory-motor coupling strength through phase-locking value (PLV) between auditory input and motor output. This study further investigated how amplitude envelope onset variations of the auditory speech signal may influence the speech auditory-motor synchronization. Sixty Mandarin-speaking adults listened to a stream of randomly presented syllables at an increasing speed while concurrently whispering in synchrony with the rhythm of the auditory stimuli whose onset consistency was manipulated, consisting of aspirated, unaspirated, and mixed conditions. The participants' PLVs for the three conditions in the SSS test were derived and compared. Results showed that syllable rise time affected the speech auditory-motor synchronization in a bifurcated fashion. Specifically, PLVs were significantly higher in the temporally more consistent conditions (aspirated or unaspirated) than those in the less consistent condition (mixed) for high synchronizers. In contrast, low synchronizers tended to be immune to the onset consistency. Overall, these results validated how syllable onset consistency in the rise time of amplitude envelope may modulate the strength of speech auditory-motor coupling. This study supports the application of the SSS test to examine individual differences in the integration of perception and production systems, which has implications for those with speech and language disorders that have difficulty with processing speech onset characteristics such as rise time.

Auditory-motor synchronization varies among individuals and is critically shaped by acoustic features

The ability to synchronize body movements with quasi-regular auditory stimuli represents a fundamental trait in humans at the core of speech and music. Despite the long trajectory of the study of such ability, little attention has been paid to how acoustic features of the stimuli and individual differences can modulate auditory-motor synchrony. Here, by exploring auditory-motor synchronization abilities across different effectors and types of stimuli, we revealed that this capability is more restricted than previously assumed. While the general population can synchronize to sequences composed of the repetitions of the same acoustic unit, the synchrony in a subgroup of participants is impaired when the unit's identity varies across the sequence. In addition, synchronization in this group can be temporarily restored by being primed by a facilitator stimulus. Auditory-motor integration is stable across effectors, supporting the hypothesis of a central clock mechanism subserving the different articulators but critically shaped by the acoustic features of the stimulus and individual abilities.

Explaining flexible continuous speech comprehension from individual motor rhythms

When speech is too fast, the tracking of the acoustic signal along the auditory pathway deteriorates, leading to suboptimal speech segmentation and decoding of speech information. Thus, speech comprehension is limited by the temporal constraints of the auditory system. Here we ask whether individual differences in auditory-motor coupling strength in part shape these temporal constraints. In two behavioural experiments, we characterize individual differences in the comprehension of naturalistic speech as function of the individual synchronization between the auditory and motor systems and the preferred frequencies of the systems. Obviously, speech comprehension declined at higher speech rates. Importantly, however, both higher auditory-motor synchronization and higher spontaneous speech motor production rates were predictive of better speech-comprehension performance. Furthermore, performance increased with higher working memory capacity (digit span) and higher linguistic, model-based sentence predictability-particularly so at higher speech rates and for individuals with high auditory-motor synchronization. The data provide evidence for a model of speech comprehension in which individual flexibility of not only the motor system but also auditory-motor synchronization may play a modulatory role.

Auditory Pitch Perception in Autism Spectrum Disorder: A Systematic Review and Meta-Analysis

PURPOSE

Pitch plays an important role in auditory perception of music and language. This study provides a systematic review with meta-analysis to investigate whether individuals with autism spectrum disorder (ASD) have enhanced pitch processing ability and to identify the potential factors associated with processing differences between ASD and neurotypicals.

METHOD

We conducted a systematic search through six major electronic databases focusing on the studies that used nonspeech stimuli to provide a qualitative and quantitative assessment across existing studies on pitch perception in autism. We identified potential participant- and methodology-related moderators and conducted metaregression analyses using mixed-effects models.

RESULTS

On the basis of 22 studies with a total of 464 participants with ASD, we obtained a small-to-medium positive effect size (g = 0.26) in support of enhanced pitch perception in ASD. Moreover, the mean age and nonverbal IQ of participants were found to significantly moderate the between-studies heterogeneity.

CONCLUSIONS

Our study provides the first meta-analysis on auditory pitch perception in ASD and demonstrates the existence of different developmental trajectories between autistic individuals and neurotypicals. In addition to age, nonverbal ability is found to be a significant contributor to the lower level/local processing bias in ASD. We highlight the need for further investigation of pitch perception in ASD under challenging listening conditions. Future neurophysiological and brain imaging studies with a longitudinal design are also needed to better understand the underlying neural mechanisms of atypical pitch processing in ASD and to help guide auditory-based interventions for improving language and social functioning.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.21614271.

The Relationship Between Auditory-Motor Integration, Interoceptive Awareness, and Self-Reported Stuttering Severity

Stuttering is a neurodevelopmental speech disorder associated with motor timing that differs from non-stutterers. While neurodevelopmental disorders impacted by timing are associated with compromised auditory-motor integration and interoception, the interplay between those abilities and stuttering remains unexplored. Here, we studied the relationships between speech auditory-motor synchronization (a proxy for auditory-motor integration), interoceptive awareness, and self-reported stuttering severity using remotely delivered assessments. Results indicate that in general, stutterers and non-stutterers exhibit similar auditory-motor integration and interoceptive abilities. However, while speech auditory-motor synchrony (i.e., integration) and interoceptive awareness were not related, speech synchrony was inversely related to the speaker’s perception of stuttering severity as perceived by others, and interoceptive awareness was inversely related to self-reported stuttering impact. These findings support claims that stuttering is a heterogeneous, multi-faceted disorder such that uncorrelated auditory-motor integration and interoception measurements predicted different aspects of stuttering, suggesting two unrelated sources of timing differences associated with the disorder.