Speech Adaptation Research Articles

Молодежный сленг: восприятие глагольных заимствований носителями языка

This article presents the results of a psycholinguistic study aimed at determining the peculiarities of perception of English-language verb borrowings by Russian representatives of different age groups and professions. The research is based on the psycholinguistic theory of the word as a means of access to a single perceptual-cognitive-affective information base of a person and the concept of the specifics of the functioning of individual knowledge, developed by A.A. Zalevskaya. Quantitative indicators and qualitative analysis of the results obtained in the experiment made it possible to identify several groups of borrowed verbs depending on the level of their adaptation in the new language system. In addition, the experimental study was conducted in two stages (in the first part, stimuli were presented without context, in the second – in context), which allowed, during the analysis of the experimental results, to compare the characteristics of the identification of a borrowed English word by the subjects in a situational context and without it. The experimental material, English-language verb borrowings, is analyzed from the point of view of an individual using them: age, level of education, profession, level of knowledge /non- knowledge of a foreign language play an important role in the process of identifying words of youth slang. With age, the tolerant attitude towards borrowings decreases, while it turned out that representatives of the humanitarian professions are generally more tolerant of foreign language vocabulary than people who are professionally unrelated to language and cultural studies. With an increase in the level of education of the subjects, the speech adaptation of new borrowings is easier.

Neurophysiological evidence of sensory prediction errors driving speech sensorimotor adaptation.

The human sensorimotor system has a remarkable ability to quickly and efficiently learn movements from sensory experience. A prominent example is sensorimotor adaptation, learning that characterizes the sensorimotor system's response to persistent sensory errors by adjusting future movements to compensate for those errors. Despite being essential for maintaining and fine-tuning motor control, mechanisms underlying sensorimotor adaptation remain unclear. A component of sensorimotor adaptation is implicit (i.e., the learner is unaware of the learning process) which has been suggested to result from sensory prediction errors-the discrepancies between predicted sensory consequences of motor commands and actual sensory feedback. However, to date no direct neurophysiological evidence that sensory prediction errors drive adaptation has been demonstrated. Here, we examined prediction errors via magnetoencephalography (MEG) imaging of the auditory cortex (n = 34) during sensorimotor adaptation of speech to altered auditory feedback, an entirely implicit adaptation task. Specifically, we measured how speaking-induced suppression (SIS)--a neural representation of auditory prediction errors--changed over the trials of the adaptation experiment. SIS refers to the suppression of auditory cortical response to speech onset (in particular, the M100 response) to self-produced speech when compared to the response to passive listening to identical playback of that speech. SIS was reduced (reflecting larger prediction errors) during the early learning phase compared to the initial unaltered feedback phase. Furthermore, reduction in SIS positively correlated with behavioral adaptation extents, suggesting that larger prediction errors were associated with more learning. In contrast, such a reduction in SIS was not found in a control experiment in which participants heard unaltered feedback and thus did not adapt. In addition, in some participants who reached a plateau in the late learning phase, SIS increased (reflecting smaller prediction errors), demonstrating that prediction errors were minimal when there was no further adaptation. Together, these findings provide the first neurophysiological evidence for the hypothesis that prediction errors drive human sensorimotor adaptation.

Adults Adapt to Child Speech in Causative Semantics.

Causation is a core feature of human cognition and language. How children learn about intricate causal meanings is yet unresolved. Here, we focus on how children learn verbs that express causation. Such verbs, known as lexical causatives (e.g., break and raise), lack explicit morphosyntactic markers indicating causation, thus requiring that the child generalizes the causal meaning from the context. The language addressed to children presumably plays a crucial role in this learning process. Hence, we tested whether adults adapt their use of lexical causatives to children when talking to them in day-to-day interactions. We analyzed naturalistic longitudinal data from 12 children in the Manchester corpus (spanning from 20 to 36 months of age). To detect semantic generalization, we employed a network approach with semantics learned from cross-situational contexts. Our results show an increasing trend in the expansion of causative semantics, observable in both child speech and child-directed speech. Adults consistently maintain somewhat more intricate causative semantic networks compared to children. However, both groups display evolving patterns. Around 28-30 months of age, children undergo a reduction in the degree of causative generalization, followed by a slightly time-lagged adjustment by adults in their speech directed to children. These findings substantiate adults' adaptation in child-directed speech, extending to semantics. They highlight child-directed speech as a highly adaptive and subconscious teaching tool that facilitates the dynamic processes of languageacquisition.

Audiomotor prediction errors drive speech adaptation even in the absence of overt movement.

Observed outcomes of our movements sometimes differ from our expectations. These sensory prediction errors recalibrate the brain's internal models for motor control, reflected in alterations to subsequent movements that counteract these errors (motor adaptation). While leading theories suggest that all forms of motor adaptation are driven by learning from sensory prediction errors, dominant models of speech adaptation argue that adaptation results from integrating time-advanced copies of corrective feedback commands into feedforward motor programs. Here, we tested these competing theories of speech adaptation by inducing planned, but not executed, speech. Human speakers (male and female) were prompted to speak a word and, on a subset of trials, were rapidly cued to withhold the prompted speech. On standard trials, speakers were exposed to real-time playback of their own speech with an auditory perturbation of the first formant to induce single-trial speech adaptation. Speakers experienced a similar sensory error on movement cancelation trials, hearing a perturbation applied to a recording of their speech from a previous trial at the time they would have spoken. Speakers adapted to auditory prediction errors in both contexts, altering the spectral content of spoken vowels to counteract formant perturbations even when no actual movement coincided with the perturbed feedback. These results build upon recent findings in reaching, and suggest that prediction errors, rather than corrective motor commands, drive adaptation in speech.

Individual differences in visual pattern completion predict adaptation to degraded speech

Recognizing acoustically degraded speech relies on predictive processing whereby incomplete auditory cues are mapped to stored linguistic representations via pattern recognition processes. While listeners vary in their ability to recognize degraded speech, performance improves when a written transcription is presented, allowing completion of the partial sensory pattern to preexisting representations. Building on work characterizing predictive processing as pattern completion, we examined the relationship between domain-general pattern recognition and individual variation in degraded speech learning. Participants completed a visual pattern recognition task to measure individual-level tendency towards pattern completion. Participants were also trained to recognize noise-vocoded speech with written transcriptions and tested on speech recognition pre- and post-training using a retrieval-based transcription task. Listeners significantly improved in recognizing speech after training, and pattern completion on the visual task predicted improvement for novel items. The results implicate pattern completion as a domain-general learning mechanism that can facilitate speech adaptation in challenging contexts.

ANALYSIS OF FUNCTIONAL SPEECH ADAPTATION STRATEGIES IN MILITARY TRANSLATION

The research is focused on the aspect of functional speech adaptation of language interpreters who are gaining practical experience at the initial stage in the sphere of foreign-language military-professional communication and paying special attention to the search for original speech strategies to achieve the targets of the translation process in the most efficient way. The critical objective of the article is to theorize the functional speech adaptation and underscore the need and importance to develop interpreters’ unique creative strategies in the process of their adaptive professional maturation for the due carrying out of normal and special translation tasks under the conditions of operational military activities abroad. A detailed review of the scientific sources is carried out concerning research into definitions of linguistic terms such as: “adaptation,” “speech adaptation,” “speech strategies.” The author’s definition of the core of the term “Functional speech adaptation” is given and its main differences are outlined versus the definitions of the linguistic categories “adaptation” and “pragmatic adaptation” proposed by Russian linguistic theorists earlier. The most effective strategies for interpreting are reviewed, viz.: implementation of an interpreter’s anticipation, a strategy for target text forming from the ground of precision information, and a strategy for source text segmentation into minimal translation cells. The study applies the methods of definitional analysis, comparative analysis of theoretical principles with their generalization, theoretical synthesis of the concepts’ definitions, linguistic description method and linguistic modeling. The results of the conducted research make a significant contribution to studying functional speech adaptation of military interpreters in the implementation of interpreting and translation tasks on the foreign military sub-languages material. Moreover, the results of the study can be used for future research purposes of translation studies, theoretical and applied linguistics.

Perceptual Adaptation to Noise-Vocoded Speech by Lip-Read Information: No Difference between Dyslexic and Typical Readers.

Auditory speech can be difficult to understand but seeing the articulatory movements of a speaker can drastically improve spoken-word recognition and, on the longer-term, it helps listeners to adapt to acoustically distorted speech. Given that individuals with developmental dyslexia (DD) have sometimes been reported to rely less on lip-read speech than typical readers, we examined lip-read-driven adaptation to distorted speech in a group of adults with DD ( N = 29) and a comparison group of typical readers ( N = 29). Participants were presented with acoustically distorted Dutch words (six-channel noise-vocoded speech, NVS) in audiovisual training blocks (where the speaker could be seen) interspersed with audio-only test blocks. Results showed that words were more accurately recognized if the speaker could be seen (a lip-read advantage), and that performance steadily improved across subsequent auditory-only test blocks (adaptation). There were no group differences, suggesting that perceptual adaptation to disrupted spoken words is comparable for dyslexic and typical readers. These data open up a research avenue to investigate the degree to which lip-read-driven speech adaptation generalizes across different types of auditory degradation, and across dyslexic readers with decoding versus comprehension difficulties.

COMPARATIVE ANALYSIS OF PROSTHETIC REHABILITATION OF PATIENTS WITH COMPLETELY EDENTULOUS JAWS USING DIFFERENT OPTIONS FOR IMPLANT- SUPPORTED STRUCTURES

Objectives: To conduct a comparative analysis the effectiveness of prosthetic rehabilitation of patients with completely edentulous jaws using various options for implant-supported structures. Materials and methods: We examined and carried out complex treatment with the installation of implants in 82 patients (56 to 73 aged) years with completely edentulous jaws. All patients underwent a clinical examination and using cone beam computed tomography (CBCT) analyzed of residual bone. Patients with edentulous were rehabilitated with three implant-supported prosthetic protocols. The patient was divided into 3 groups: 21 (1grup.) patients received removable overdenture supported by 4 implants using a bar system, 19 (2grup) patients received removable overdenture supported by 4 implants using rail system of attachments, 23 (3grup) patients received fixed restorations supported by 4 implants. Peri-implant marginal bone level (MBL), immediately (base line for comparison) and 1 year, 3 years, and 5 years after implant installation, compared with values at last follow-up. The method of questioning patients was used. The assessment was carried out using a point system: chewing efficiency, ease of care and use, stability of the dentures. Quality of life, assess used the Oral health-related quality of life the OHIP-G scale. Results: In clinical follow-up the implants showed no mobility, soreness or pain during function, patients had healthy soft tissues. For patients 1group MBL after 1 year 0.82 mm, after 3 years 1.23 mm, after 5 years was 1.46 mm. For patients 2group MBL after 1 year 0.84 mm, after 3 years 1.28 mm, after 5 years was 1.49 mm. For patients 3 group MBL after 1 year 0.91 mm, after 3 years 1.32 mm, after 5 years was 1.53mm. The patients were satisfied with the result of treatment using implants. Speech adaptation of patients with removable dentures, fixed implants, occurred within a week. 5-year implants cumulative survival rate 1group rates was 96.7%, 2 group was 97.2%, 3 group rates was 96,9%. The prosthesis cumulative survival rate 1group was 96.7%, 2 group was 97.4%, 3 group was 97,6%. Conclusion: Implant-supporting structures on implants, installed between the mental foramens, are a reliable and predictable method for patients with complete edentulous jaws and significant jaw resorption. This solution is a reliable alternative to bone grafting, demonstrating fewer complications, fewer additional surgical procedures, and demonstrating satisfactory long-term survival.

Discrimination and sensorimotor adaptation of self-produced vowels in cochlear implant users.

Humans rely on auditory feedback to monitor and adjust their speech for clarity. Cochlear implants (CIs) have helped over a million people restore access to auditory feedback, which significantly improves speech production. However, there is substantial variability in outcomes. This study investigates the extent to which CI users can use their auditory feedback to detect self-produced sensory errors and make adjustments to their speech, given the coarse spectral resolution provided by their implants. First, we used an auditory discrimination task to assess the sensitivity of CI users to small differences in formant frequencies of their self-produced vowels. Then, CI users produced words with altered auditory feedback in order to assess sensorimotor adaptation to auditory error. Almost half of the CI users tested can detect small, within-channel differences in their self-produced vowels, and they can utilize this auditory feedback towards speech adaptation. An acoustic hearing control group showed better sensitivity to the shifts in vowels, even in CI-simulated speech, and elicited more robust speech adaptation behavior than the CI users. Nevertheless, this study confirms that CI users can compensate for sensory errors in their speech and supports the idea that sensitivity to these errors may relate to variability in production.

Speech adaptation in conversation: Effects of segment cue-weighting strategy for non-native speakers

Research has investigated how speakers make phonetic adaptations by adjusting their speech sounds to either converge to or diverge from their interlocutor’s. Less is known about the dynamic adaptive strategies non-native speakers use to improve intelligibility when interacting with native speakers, particularly how their strategies change over the course of spontaneous conversations. The current study examines phonetic adaptations in English words contrasting tense and lax vowels (e.g., sheep-ship) in unscripted conversations between non-native Japanese English and native English speakers during an engaging computer game task. Japanese speakers have previously been found to rely on temporal cues (vowel length) for tensity distinctions due to their L1 cue-weighting strategy rather than spectral cues (vowel quality) that are predominantly used in English. Acoustic analyses are conducted to examine changes in non-native vowel productions before, during and after the conversation task. We predict that, in an attempt to overcome miscommunication, non-native speakers may initially lengthen the tense vowels to distinguish them from their lax counterparts. As the conversation progresses, non-native speakers may adapt to a more native-like cue-weighting pattern by shifting to spectral distinctions. Results are discussed in terms of adaptations to cue-weighting strategies for intelligibility gains by interlocutors of different linguistic backgrounds.

Real-time speech adaptations in conversations between human interlocutor and AI confederate

Compared to human-directed adaptations, less is known about how humans adjust their speech for intelligibility benefits while interacting with an AI-powered voice interface. In this study, we investigate human speech adaptations in human-to-human versus human-to-AI unscripted conversations. Specifically, we examine the production of words containing intervocalic /t-d/ in a conversation between a speaker who distinguishes these two stops (e.g., metal–medal) and a speaker (“flapper”) who merges the two stops into a flap /ɾ/. We predict that misperceptions of intervocalic /t-d/ may cause confusions, thus motivating adaptations. We record native Canadian-English speakers (flappers) while playing a video game on Zoom in two conversation settings: with (1) a human non-flapper and (2) an AI non-flapper (computer-generated speech). Acoustic analyses of the productions by human flapper speakers include features specific to stop-flap distinctions as well as global features (e.g., overall duration). In both human- and AI-directed speech, we expect human interlocutors to change flapped productions to stops to enhance intelligibility, particularly late in the conversation. Moreover, we expect differences between human- and AI-directed adaptations, with the former dominantly employing sound-specific features and the latter relying more on global hyperarticulation. Understanding these interlocutor-oriented adaptations may inform the technology behind human-computer interfaces.

Effects of training length on adaptation to noise-vocoded speech.

Listeners show rapid perceptual learning of acoustically degraded speech, though the amount of exposure required to maximize speech adaptation is unspecified. The current work used a single-session design to examine the length of auditory training on perceptual learning for normal hearing listeners exposed to eight-channel noise-vocoded speech. Participants completed short, medium, or long training using a two-alternative forced choice sentence identification task with feedback. To assess learning and generalization, a 40-trial pre-test and post-test transcription task was administered using trained and novel sentences. Training results showed all groups performed near ceiling with no reliable differences. For test data, we evaluated changes in transcription accuracy using separate linear mixed models for trained or novel sentences. In both models, we observed a significant improvement in transcription at post-test relative to pre-test. Critically, the three training groups did not differ in the magnitude of improvement following training. Subsequent Bayes factors analysis evaluating the test by group interaction provided strong evidence in support of the null hypothesis. For these stimuli and procedure, results suggest increased training does not necessarily maximize learning outcomes; both passive and trained experience likely supported adaptation. Findings may contribute to rehabilitation recommendations for listeners adapting to degraded speech signals.

A new experimental design to study speech adaptations in spontaneous human-computer conversations

Interest is growing for how human interlocutors make phonetic adaptations during spontaneous conversations. Given the increasing popularity of AI chatbots, research also needs to account for adaptations in human–computer interactions, an area under-investigated presumably due to methodological challenges in generating controlled conversational responses. Most studies involve scripted computer output, which may obstruct the dynamicity and the oral–aural medium of a natural conversation. To circumvent these constraints, we present a new experimental design that generates unscripted audio computer responses in human–computer conversations during a collaborative game played on Zoom. This design is unique in several aspects. First, the game (Escape Room) requires discussions on placing pictures (depicting target words/sounds) in specific locations, where misperceptions of target words between interlocutors may cause confusions, thus motivating natural adaptations. Second, to enable real-time computer responses, we adopt the wizard-of-oz paradigm typically used in the field of human–computer interaction, where a human confederate inputs text responses behind-the-scenes. Third, a programmable text-to-speech synthesizer converts the text input to audio output. The design demonstrated in this presentation opens the door to new analyses, tracking the dynamicity of speech adjustments over time. Moreover, it is generalizable to studying speech adaptations across interlocutor backgrounds.

Listening effort for L2 accents: Adults’ adaptation to Mandarin accented english

Using task-evoked pupillary response (TEPR) and dual-task procedures, prior research has shown that adults recruit additional cognitive resources when processing fully intelligible L2-accented speech compared to speech in their own L1 accent (McLaughlin and Van Engen, 2020; Brown et al., 2020). In this study, we investigated the relationship between three prosodic measures (relative word duration variance, pitch stability, and pitch range) and changes in listening effort for L1 and L2 speakers over the course of an experiment. Using growth curve analysis, we found significant interactions between each of the three measures and trial number, indicating that prosodic factors influence speech adaptation. However, these interactions were in opposite directions for the L1 and L2 speakers. Thus, adult monolingual English listeners rely on prosodic information to adapt to a particular speaker’s voice, but use that information differently based on speaker identity.

Breathing and Speech Adaptation: Do Speakers Adapt Toward a Confederate Talking Under Physical Effort?

This study investigated whether speakers adapt their breathing and speech (fundamental frequency [fo]) to a prerecorded confederate who is sitting or moving under different levels of physical effort and who is either speaking or not. Following Paccalin and Jeannerod (2000), we would expect breathing rate to change in the direction of the confederate's, even if the participant is physically inactive. This might in turn affect their speech acoustics. We recorded the speech and respiration of 22 native German speakers. They produced solo and synchronous read speech in interaction with a confederate who appeared on a prerecorded video. There were three within-subject experimental conditions: the confederate (a) sitting, (b) biking with light effort, or (c) biking with heavier effort. During speech, the confederate's inhalation amplitude and fo increased with physical effort, as expected. Her breath cycle duration changed differently, probably because of read speech constraints. Overall, the only adaptation the participants showed was higher fo with increase in the confederate's physical effort during synchronous, but not solo, speech. Additionally, they produced shallower inhalations when observing the confederate biking in silence, as compared to the condition without movement. Crucially, the participants' acoustic and breathing data showed large interindividual variability. Our findings indicate that, in this paradigm, convergence only took place on fo during synchronous speech and that this phonetic adaptation happened independently from any speech breathing adaptation. It also suggests that participants may adapt their quiet breathing while watching a person performing physical exercise but that the mechanism is more complex than that explained previously.

Comparison of speech changes caused by four different orthodontic retainers: a crossover randomized clinical trial.

This study aimed to compare the influence of four different maxillary removable orthodontic retainers on speech. Eligibility criteria for sample selection were: 20-40-year subjects with acceptable occlusion, native speakers of Portuguese. The volunteers (n=21) were divided in four groups randomized with a 1:1:1:1 allocation ratio. The four groups used, in random order, the four types of retainers full-time for 21 days each, with a washout period of 7-days. The removable maxillary retainers were: conventional wraparound, wraparound with an anterior hole, U-shaped wraparound, and thermoplastic retainer. Three volunteers were excluded. The final sample comprised 18 subjects (11 male; 7 female) with mean age of 27.08 years (SD=4.65). The speech evaluation was performed in vocal excerpts recordings made before, immediately after, and 21 days after the installation of each retainer, with auditory-perceptual and acoustic analysis of formant frequencies F1 and F2 of the vowels. Repeated measures ANOVA and Friedman with Tukey tests were used for statistical comparison. Speech changes increased immediately after conventional wraparound and thermoplastic retainer installation, and reduced after 21 days, but not to normal levels. However, this increase was statistically significant only for the wraparound with anterior hole and the thermoplastic retainer. Formant frequencies of vowels were altered at initial time, and the changes remained in conventional, U-shaped and thermoplastic appliances after three weeks. The thermoplastic retainer was more harmful to the speech than wraparound appliances. The conventional and U-shaped retainers interfered less in speech. The three-week period was not sufficient for speech adaptation.

From first encounters to longitudinal exposure: a repeated exposure-test paradigm for monitoring speech adaptation.

Perceptual difficulty with an unfamiliar accent can dissipate within short time scales (e.g., within minutes), reflecting rapid adaptation effects. At the same time, long-term familiarity with an accent is also known to yield stable perceptual benefits. However, whether the long-term effects reflect sustained, cumulative progression from shorter-term adaptation remains unknown. To fill this gap, we developed a web-based, repeated exposure-test paradigm. In this paradigm, short test blocks alternate with exposure blocks, and this exposure-test sequence is repeated multiple times. This design allows for the testing of adaptive speech perception both (a) within the first moments of encountering an unfamiliar accent and (b) over longer time scales such as days and weeks. In addition, we used a Bayesian ideal observer approach to select natural speech stimuli that increase the statistical power to detect adaptation. The current report presents results from a first application of this paradigm, investigating changes in the recognition accuracy of Mandarin-accented speech by native English listeners over five sessions spanning 3 weeks. We found that the recognition of an accent feature (a syllable-final /d/, as in feed, sounding/t/-like) improved steadily over the three-week period. Unexpectedly, however, the improvement was seen with or without exposure to the accent. We discuss possible reasons for this result and implications for conducting future longitudinal studies with repeated exposure and testing.

The process of reacquiring new vocalization in total laryngectomy patients with head and neck cancer: A qualitative study

ObjectiveSpeech rehabilitation significantly contributes to the enhanced quality of life for patients who have undergone laryngectomy due to head and neck cancer. The initiation of tracheoesophageal speech early in the rehabilitation process has been associated with improved speech quality. Despite this, voice changes can carry a stigma due to communication challenges, even after successful voice restoration, potentially limiting the overall improvement in quality of life. Thus, our aim was to gain a profound understanding of the transition process from the selection to the adaptation of tracheoesophageal speech in patients with head and neck cancer. MethodsParticipants, who had undergone laryngectomy for head and neck cancer, were recruited from peer support groups in Japan, resulting in the identification of thirteen tracheoesophageal speakers. The data were analyzed using grounded theory methodology, incorporating open, axial, and selective coding. Semi-structured interviews delved into tracheoesophageal speakers' perceptions of their voices and the adaptive strategies employed for their preferred alternative communication methods. ResultsDuring the adaptation process, participants underscored the importance of communicating with their own voices. However, they also experienced anxiety about losing their natural voice, confronted the reality of living without a voice, and coped with their new voice. Eventually, participants came to recognize the changed voice as their own. ConclusionsThe personal conviction associated with the notion of “communicating with one's own voice” is integral to the adaptation process for patients with head and neck cancer who undergo laryngectomies and utilize tracheoesophageal speech. Some aspects of tracheoesophageal speech can evoke feelings of hopelessness, emphasizing the importance of comprehensive support for professional speech rehabilitation.

Languages in China link climate, voice quality, and tone in a causal chain

Are the sound systems of languages ecologically adaptive like other aspects of human behavior? In previous substantive explorations of the climate–language nexus, the hypothesis that desiccation affects the tone systems of languages was not well supported. The lack of analysis of voice quality data from natural speech undermines the credibility of the following two key premises: the compromised voice quality caused by desiccated ambient air and constrained use of phonemic tone due to a desiccated larynx. Here, the full chain of causation, humidity → voice quality → number of tones, is for the first time strongly supported by direct experimental tests based on a large speech database (China’s Language Resources Protection Project). Voice quality data is sampled from a recording set that includes 997 language varieties in China. Each language is represented by about 1200 sound files, amounting to a total of 1,174,686 recordings. Tonally rich languages are distributed throughout China and vary in their number of tones and in the climatic conditions of their speakers. The results show that, first, the effect of humidity is large enough to influence the voice quality of common speakers in a naturalistic environment; secondly, poorer voice quality is more likely to be observed in speakers of non-tonal languages and languages with fewer tones. Objective measures of phonatory capabilities help to disentangle the humidity effect from the contribution of phylogenetic and areal relatedness to the tone system. The prediction of ecological adaptation of speech is first verified through voice quality analysis. Humidity is observed to be related to synchronic variation in tonality. Concurrently, the findings offer a potential trigger for diachronic changes in tone systems.

Mechanisms of sensorimotor adaptation in a hierarchical state feedback control model of speech.

Upon perceiving sensory errors during movements, the human sensorimotor system updates future movements to compensate for the errors, a phenomenon called sensorimotor adaptation. One component of this adaptation is thought to be driven by sensory prediction errors-discrepancies between predicted and actual sensory feedback. However, the mechanisms by which prediction errors drive adaptation remain unclear. Here, auditory prediction error-based mechanisms involved in speech auditory-motor adaptation were examined via the feedback aware control of tasks in speech (FACTS) model. Consistent with theoretical perspectives in both non-speech and speech motor control, the hierarchical architecture of FACTS relies on both the higher-level task (vocal tract constrictions) as well as lower-level articulatory state representations. Importantly, FACTS also computes sensory prediction errors as a part of its state feedback control mechanism, a well-established framework in the field of motor control. We explored potential adaptation mechanisms and found that adaptive behavior was present only when prediction errors updated the articulatory-to-task state transformation. In contrast, designs in which prediction errors updated forward sensory prediction models alone did not generate adaptation. Thus, FACTS demonstrated that 1) prediction errors can drive adaptation through task-level updates, and 2) adaptation is likely driven by updates to task-level control rather than (only) to forward predictive models. Additionally, simulating adaptation with FACTS generated a number of important hypotheses regarding previously reported phenomena such as identifying the source(s) of incomplete adaptation and driving factor(s) for changes in the second formant frequency during adaptation to the first formant perturbation. The proposed model design paves the way for a hierarchical state feedback control framework to be examined in the context of sensorimotor adaptation in both speech and non-speech effector systems.