Beyond Broca: Neural Architecture and Evolution of a Dual Motor Speech Coordination System

Classical neural architecture models of speech production propose a single system coordinating all the vocal articulators from lips to larynx. Here we propose a dual coordination system in which laryngeal control of pitch-related aspects of prosody and song are controlled by a dorsal premotor system while supralaryngeal articulation at the phonetic/syllabic level is controlled by a ventral premotor system. The separability of these neural systems supports models of the evolution of speech and language in which song-based communication was an early foundational stage.

Persuasive conversation as a new form of communication in Homo sapiens

The aim of this paper is twofold: to propose that conversation is the distinctive feature of Homo sapiens ' communication; and to show that the emergence of modern language is tied to the transition from pantomime to verbal and grammatically complex forms of narrative. It is suggested that (animal and human) communication is a form of persuasion and that storytelling was the best tool developed by humans to convince others. In the early stage of communication, archaic hominins used forms of pantomimic storytelling to persuade others. Although pantomime is a powerful tool for persuasive communication , it is proposed that it is not an effective tool for persuasive conversation : conversation is characterized by a form of reciprocal persuasion among peers; instead, pantomime has a mainly asymmetrical character. The selective pressure towards persuasive reciprocity of the conversational level is the evolutionary reason that allowed the transition from pantomime to grammatically complex codes in H. sapiens , which favoured the evolution of speech. This article is part of the theme issue ‘Reconstructing prehistoric languages’.

Primate Vocal Communication and the Evolution of Speech

Studies of nonhuman primate communication are often motivated by the desire to shed light on the evolution of speech. In contrast to human speech, the vocal repertoires of nonhuman primates are evolutionarily highly conserved. Within species-specific constraints, calls may vary in relation to the internal state of the caller or social experience. Receivers can use signalers’ calls to predict upcoming events or behavioral dispositions. Yet nonhuman primates do not appear to express or comprehend communicative or informative intent. Signalers are sensitive to the relation between their own actions and receivers’ responses, and thus, signaling behavior can be conceived as goal directed. Receivers’ ability to integrate information from multiple sources renders the system flexible and powerful. Researchers who take a linguistic or biological perspective on nonhuman primate communication should be aware of the strengths and limitations of their approaches. Both benefit from a focus on the mechanisms that underpin signaling and responses to signals.

Human larynx motor cortices coordinates respiration for vocal-motor control

Vocal flexibility is a hallmark of the human species, most particularly the capacity to speak and sing. The human motor system is unique in having two separate representations of the laryngeal muscles, where only one would be expected. The dorsal larynx area is known to integrate respiratory function which is provides a powerful mechanism in support of speech motor control, while less is known about the contributions of the ventral larynx. We localised the dorsal and ventral larynx motor cortices by having participants sing wordless melodies while undergoing ultra-high field functional magnetic resonance imaging and tested the involvement of respiratory motor control in the same regions by having participants whistle simple melodies. Surprisingly, both singing and whistling increased activation of both ‘larynx areas’ despite the lack of involvement of the larynx during whistling. We provide the first evidence that this level of integration is not exclusive to the dLMC, suggesting a greater role of the vLMC in the evolution of speech than previously supposed. With this broader understanding of the human vocal-motor system, we outline predictions about the descending motor pathways that give these cortical areas access to both the laryngeal and respiratory systems.

Chimpanzee lip-smacks confirm primate continuity for speech-rhythm evolution

Speech is a human hallmark, but its evolutionary origins continue to defy scientific explanation. Recently, the open–close mouth rhythm of 2–7 Hz (cycles/second) characteristic of all spoken languages has been identified in the orofacial signals of several nonhuman primate genera, including orangutans, but evidence from any of the African apes remained missing. Evolutionary continuity for the emergence of speech is, thus, still inconclusive. To address this empirical gap, we investigated the rhythm of chimpanzee lip-smacks across four populations (two captive and two wild). We found that lip-smacks exhibit a speech-like rhythm at approximately 4 Hz, closing a gap in the evidence for the evolution of speech-rhythm within the primate order. We observed sizeable rhythmic variation within and between chimpanzee populations, with differences of over 2 Hz at each level. This variation did not result, however, in systematic group differences within our sample. To further explore the phylogenetic and evolutionary perspective on this variability, inter-individual and inter-population analyses will be necessary across primate species producing mouth signals at speech-like rhythm. Our findings support the hypothesis that speech recruited ancient primate rhythmic signals and suggest that multi-site studies may still reveal new windows of understanding about these signals' use and production along the evolutionary timeline of speech.

Artificial Techniques for Language Disorders

<p class="0abstract">This review focuses on artificial techniques which include the artificial intelligent techniques and applications, the robot technology and the serious games supporting the procedure of learning and teaching of language disorders and deficits as well the evolution of speech. Especially, the written language, the oral language and the phoneme pronunciations, the communication and consequently the social interaction are benefited and are assisted by these achievements of technology.</p>

Towards a new taxonomy of primate vocal production learning

The extent to which vocal learning can be found in nonhuman primates is key to reconstructing the evolution of speech. Regarding the adjustment of vocal output in relation to auditory experience (vocal production learning in the narrow sense), effects on the ontogenetic trajectory of vocal development as well as adjustment to group-specific call features have been found. Yet, a comparison of the vocalizations of different primate genera revealed striking similarities in the structure of calls and repertoires in different species of the same genus, indicating that the structure of nonhuman primate vocalizations is highly conserved. Thus, modifications in relation to experience only appear to be possible within relatively tight species-specific constraints. By contrast, comprehension learning may be extremely rapid and open-ended. In conjunction, these findings corroborate the idea of an ancestral independence of vocal production and auditory comprehension learning. To overcome the futile debate about whether or not vocal production learning can be found in nonhuman primates, we suggest putting the focus on the different mechanisms that may mediate the adjustment of vocal output in response to experience; these mechanisms may include auditory facilitation and learning from success. This article is part of the theme issue ‘What can animal communication teach us about human language?’

Behaviour, biology and evolution of vocal learning in bats

The comparative approach can provide insight into the evolution of human speech, language and social communication by studying relevant traits in animal systems. Bats are emerging as a model system with great potential to shed light on these processes given their learned vocalizations, close social interactions, and mammalian brains and physiology. A recent framework outlined the multiple levels of investigation needed to understand vocal learning across a broad range of non-human species, including cetaceans, pinnipeds, elephants, birds and bats. Here, we apply this framework to the current state-of-the-art in bat research. This encompasses our understanding of the abilities bats have displayed for vocal learning, what is known about the timing and social structure needed for such learning, and current knowledge about the prevalence of the trait across the order. It also addresses the biology (vocal tract morphology, neurobiology and genetics) and evolution of this trait. We conclude by highlighting some key questions that should be answered to advance our understanding of the biological encoding and evolution of speech and spoken communication. This article is part of the theme issue ‘What can animal communication teach us about human language?’

Evolution of Speech: Anatomy and Control

Purpose This article critically reviews work on the evolution of speech in the context of motor control. It presents a brief introduction to the field of language evolution, of which the study of the evolution of speech is an integral component, and argues why taking the evolutionary perspective is useful. It then proceeds to review different methods of studying evolutionary questions: comparative research, experimental and observational research, and computer and mathematical modeling. Conclusions On the basis of comparative analysis of related species (specifically, other great apes) and on the basis of theoretical results, this article argues that adaptations for speech must have evolved gradually and that it is likely that speech motor control is one of the key aspects that has undergone observable selection related to speech, because, in this area, all the necessary precursors are present in closely related species. This implies that it must be possible to find empirical evidence for how speech evolved in the area of speech motor control. However, such research is only in its infancy at the present moment.