How Network Structure Shapes Languages: Disentangling the Factors Driving Variation in Communicative Agents.

Languages show substantial variability between their speakers, but it is currently unclear how the structure of the communicative network contributes to the patterning of this variability. While previous studies have highlighted the role of network structure in language change, the specific aspects of network structure that shape language variability remain largely unknown. To address this gap, we developed a Bayesian agent-based model of language evolution, contrasting between two distinct scenarios: language change and language emergence. By isolating the relative effects of specific global network metrics across thousands of simulations, we show that global characteristics of network structure play a critical role in shaping interindividual variation in language, while intraindividual variation is relatively unaffected. We effectively challenge the long-held belief that size and density are the main network structural factors influencing language variation, and show that path length and clustering coefficient are the main factors driving interindividual variation. In particular, we show that variation is more likely to occur in populations where individuals are not well-connected to each other. Additionally, variation is more likely to emerge in populations that are structured in small communities. Our study provides potentially important insights into the theoretical mechanisms underlying language variation.

Histological and magnetic resonance imaging assessment of Liqoseal in a spinal in vivo pig model.

BACKGROUND: Liqoseal (Polyganics, B.V.) is a dural sealant patch for preventing postoperative cerebrospinal fluid (CSF) leakage. It has been extensively tested preclinically and CE (Conformité Européenne) approved for human use after a first cranial in-human study. However, the safety of Liqoseal for spinal application is still unknown. The aim of this study was to assess the safety of spinal Liqoseal application compared with cranial application using histology and magnetic resonance imaging characteristics. METHODS: Eight female Dutch Landrace pigs underwent laminectomy, durotomy with standard suturing and Liqoseal application. Three control animals underwent the same procedure without sealant application. The histological characteristics and imaging characteristics of animals with similar survival times were compared to data from a previous cranial porcine model. RESULTS: Similar foreign body reactions were observed in spinal and cranial dura. The foreign body reaction consisted of neutrophils and reactive fibroblasts in the first 3 days, changing to a chronic granulomatous inflammatory reaction with an increasing number of macrophages and lymphocytes and the formation of a fibroblast layer on the dura by day 7. Mean Liqoseal plus dura thickness reached a maximum of 1.2 mm (range 0.7-2.0 mm) at day 7. CONCLUSION: The spinal dural histological reaction to Liqoseal during the first 7 days was similar to the cranial dural reaction. Liqoseal did not swell significantly in both application areas over time. Given the current lack of a safe and effective dural sealant for spinal application, we propose that an in-human safety study of Liqoseal is the logical next step.

The Sutureless Excimer Laser Anastomosis Clip Pilot Study: a feasibility and safety study.

BACKGROUND: The excimer laser-assisted non-occlusive anastomosis (ELANA) bypass technique may have the advantage of its non-occlusive design in the treatment of last-resort cases where endovascular treatment or direct clipping is considered to be unsafe. However, the technique remains technically challenging. Therefore, a sutureless ELANA Clip device (SEcl) was developed to simplify the technique avoiding tedious anastomosis stitching in depth. The present study investigates the clinical feasibility and safety of the SEcl technique. METHODS: Three patients with complex and large aneurysms in the anterior circulation were selected after multidisciplinary consensus that the aneurysms were too complex for endovascular or direct clipping treatment options. Bypass surgery was considered as a last-resort treatment option, and after preoperative evaluation and informed consent, SEcl bypass surgery was performed. Applicability, technical aspects and patient outcomes are assessed. RESULTS: All aneurysms were excluded from the circulation. The creation of the intracranial anastomosis was easier and faster. No device-related serious adverse events were encountered, and all outcomes were favorable (one patient stable Modified Rankin Scale, two patients improved). CONCLUSION: The SEcl anastomosis technique is feasible and, considering the severity of the disease, relatively safe. It can be considered a treatment option in very difficult-to treat last-resort aneurysm cases. From this study, further developments in minimizing clip size and application in cardiac surgery are initiated.

Spinal fixation after laminectomy in pigs prevents postoperative spinal cord injury.

BACKGROUND: A safe, effective, and ethically sound animal model is essential for preclinical research to investigate spinal medical devices. We report the initial failure of a porcine spinal survival model and a potential solution by fixating the spine. METHODS: Eleven female Dutch Landrace pigs underwent a spinal lumbar interlaminar decompression with durotomy and were randomized for implantation of a medical device or control group. Magnetic resonance imaging (MRI) was performed before termination. RESULTS: Neurological deficits were observed in 6 out of the first 8 animals. Three of these animals were terminated prematurely because they reached the predefined humane endpoint. Spinal cord compression and myelopathy was observed on postoperative MRI imaging. We hypothesized postoperative spinal instability with epidural hematoma, inherent to the biology of the model, and subsequent spinal cord injury as a potential cause. In the subsequent 3 animals, we fixated the spine with Lubra plates. All these animals recovered without neurological deficits. The extent of spinal cord compression on MRI was variable across animals and did not seem to correspond well with neurological outcome. CONCLUSION: This study shows that in a porcine in vivo model of interlaminar decompression and durotomy, fixation of the spine after lumbar interlaminar decompression is feasible and may improve neurological outcomes. Additional research is necessary to evaluate this hypothesis.

Detrending the Waveforms of Steady-State Vowels.

Steady-state vowels are vowels that are uttered with a momentarily fixed vocal tract configuration and with steady vibration of the vocal folds. In this steady-state, the vowel waveform appears as a quasi-periodic string of elementary units called pitch periods. Humans perceive this quasi-periodic regularity as a definite pitch. Likewise, so-called pitch-synchronous methods exploit this regularity by using the duration of the pitch periods as a natural time scale for their analysis. In this work, we present a simple pitch-synchronous method using a Bayesian approach for estimating formants that slightly generalizes the basic approach of modeling the pitch periods as a superposition of decaying sinusoids, one for each vowel formant, by explicitly taking into account the additional low-frequency content in the waveform which arises not from formants but rather from the glottal pulse. We model this low-frequency content in the time domain as a polynomial trend function that is added to the decaying sinusoids. The problem then reduces to a rather familiar one in macroeconomics: estimate the cycles (our decaying sinusoids) independently from the trend (our polynomial trend function); in other words, detrend the waveform of steady-state waveforms. We show how to do this efficiently.

Evolutionary Dynamics Do Not Motivate a Single-Mutant Theory of Human Language.

One of the most controversial hypotheses in cognitive science is the Chomskyan evolutionary conjecture that language arose instantaneously in humans through a single mutation. Here we analyze the evolutionary dynamics implied by this hypothesis, which has never been formalized before. The hypothesis supposes the emergence and fixation of a single mutant (capable of the syntactic operation Merge) during a narrow historical window as a result of frequency-independent selection under a huge fitness advantage in a population of an effective size no larger than ~15 000 individuals. We examine this proposal by combining diffusion analysis and extreme value theory to derive a probabilistic formulation of its dynamics. We find that although a macro-mutation is much more likely to go to fixation if it occurs, it is much more unlikely a priori than multiple mutations with smaller fitness effects. The most likely scenario is therefore one where a medium number of mutations with medium fitness effects accumulate. This precise analysis of the probability of mutations occurring and going to fixation has not been done previously in the context of the evolution of language. Our results cast doubt on any suggestion that evolutionary reasoning provides an independent rationale for a single-mutant theory of 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.

Ontogeny of vocal rhythms in harbor seal pups: an exploratory study.

Puppyhood is a very active social and vocal period in a harbor seal's life Phoca vitulina. An important feature of vocalizations is their temporal and rhythmic structure, and understanding vocal timing and rhythms in harbor seals is critical to a cross-species hypothesis in evolutionary neuroscience that links vocal learning, rhythm perception, and synchronization. This study utilized analytical techniques that may best capture rhythmic structure in pup vocalizations with the goal of examining whether (1) harbor seal pups show rhythmic structure in their calls and (2) rhythms evolve over time. Calls of 3 wild-born seal pups were recorded daily over the course of 1-3 weeks; 3 temporal features were analyzed using 3 complementary techniques. We identified temporal and rhythmic structure in pup calls across different time windows. The calls of harbor seal pups exhibit some degree of temporal and rhythmic organization, which evolves over puppyhood and resembles that of other species' interactive communication. We suggest next steps for investigating call structure in harbor seal pups and propose comparative hypotheses to test in other pinniped species.

A coil in the hair-a case report of percutaneous coil migration.

Coil migration following cerebral aneurysm treatment has been described and may result in stroke, recurrent aneurysm, or local mass effect. Cerebral coil embolization is also applied in arteriovenous malformations and arteriovenous fistulas, but these pathologies are relatively rare and coil migration is not as well described. Furthermore, these cases are more commonly treated with combinations of multiple modalities to achieve cure. Embolization, surgery, and radiation each have risks and benefits and combinations may have synergistic risks and benefits not seen in monotherapy. We report a case of extravascular and extra-corporeal coil migration after embolization and craniectomy to treat a patient with hemorrhage from an arteriovenous fistula.

Biology-Culture Co-evolution in Finite Populations.

Language is the result of two concurrent evolutionary processes: biological and cultural inheritance. An influential evolutionary hypothesis known as the moving target problem implies inherent limitations on the interactions between our two inheritance streams that result from a difference in pace: the speed of cultural evolution is thought to rule out cognitive adaptation to culturally evolving aspects of language. We examine this hypothesis formally by casting it as as a problem of adaptation in time-varying environments. We present a mathematical model of biology-culture co-evolution in finite populations: a generalisation of the Moran process, treating co-evolution as coupled non-independent Markov processes, providing a general formulation of the moving target hypothesis in precise probabilistic terms. Rapidly varying culture decreases the probability of biological adaptation. However, we show that this effect declines with population size and with stronger links between biology and culture: in realistically sized finite populations, stochastic effects can carry cognitive specialisations to fixation in the face of variable culture, especially if the effects of those specialisations are amplified through cultural evolution. These results support the view that language arises from interactions between our two major inheritance streams, rather than from one primary evolutionary process that dominates another.

Humans recognize emotional arousal in vocalizations across all classes of terrestrial vertebrates: evidence for acoustic universals.

Writing over a century ago, Darwin hypothesized that vocal expression of emotion dates back to our earliest terrestrial ancestors. If this hypothesis is true, we should expect to find cross-species acoustic universals in emotional vocalizations. Studies suggest that acoustic attributes of aroused vocalizations are shared across many mammalian species, and that humans can use these attributes to infer emotional content. But do these acoustic attributes extend to non-mammalian vertebrates? In this study, we asked human participants to judge the emotional content of vocalizations of nine vertebrate species representing three different biological classes-Amphibia, Reptilia (non-aves and aves) and Mammalia. We found that humans are able to identify higher levels of arousal in vocalizations across all species. This result was consistent across different language groups (English, German and Mandarin native speakers), suggesting that this ability is biologically rooted in humans. Our findings indicate that humans use multiple acoustic parameters to infer relative arousal in vocalizations for each species, but mainly rely on fundamental frequency and spectral centre of gravity to identify higher arousal vocalizations across species. These results suggest that fundamental mechanisms of vocal emotional expression are shared among vertebrates and could represent a homologous signalling system.

Response to Lieberman on "Monkey vocal tracts are speech-ready".

Macaques do have a speech-ready vocal tract, but lack a speech-ready brain to control it.

Signal dimensionality and the emergence of combinatorial structure.

In language, a small number of meaningless building blocks can be combined into an unlimited set of meaningful utterances. This is known as combinatorial structure. One hypothesis for the initial emergence of combinatorial structure in language is that recombining elements of signals solves the problem of overcrowding in a signal space. Another hypothesis is that iconicity may impede the emergence of combinatorial structure. However, how these two hypotheses relate to each other is not often discussed. In this paper, we explore how signal space dimensionality relates to both overcrowding in the signal space and iconicity. We use an artificial signalling experiment to test whether a signal space and a meaning space having similar topologies will generate an iconic system and whether, when the topologies differ, the emergence of combinatorially structured signals is facilitated. In our experiments, signals are created from participants' hand movements, which are measured using an infrared sensor. We found that participants take advantage of iconic signal-meaning mappings where possible. Further, we use trajectory predictability, measures of variance, and Hidden Markov Models to measure the use of structure within the signals produced and found that when topologies do not match, then there is more evidence of combinatorial structure. The results from these experiments are interpreted in the context of the differences between the emergence of combinatorial structure in different linguistic modalities (speech and sign).

Evolution of speech and evolution of language.

Speech is the physical signal used to convey spoken language. Because of its physical nature, speech is both easier to compare with other species' behaviors and easier to study in the fossil record than other aspects of language. Here I argue that convergent fossil evidence indicates adaptations for complex vocalizations at least as early as the common ancestor of Neanderthals and modern humans. Furthermore, I argue that it is unlikely that language evolved separately from speech, but rather that gesture, speech, and song coevolved to provide both a multimodal communication system and a musical system. Moreover, coevolution must also have played a role by allowing both cognitive and anatomical adaptations to language and speech to evolve in parallel. Although such a coevolutionary scenario is complex, it is entirely plausible from a biological point of view.

More than words (and faces): evidence for a Stroop effect of prosody in emotion word processing.

Humans typically combine linguistic and nonlinguistic information to comprehend emotions. We adopted an emotion identification Stroop task to investigate how different channels interact in emotion communication. In experiment 1, synonyms of "happy" and "sad" were spoken with happy and sad prosody. Participants had more difficulty ignoring prosody than ignoring verbal content. In experiment 2, synonyms of "happy" and "sad" were spoken with happy and sad prosody, while happy or sad faces were displayed. Accuracy was lower when two channels expressed an emotion that was incongruent with the channel participants had to focus on, compared with the cross-channel congruence condition. When participants were required to focus on verbal content, accuracy was significantly lower also when prosody was incongruent with verbal content and face. This suggests that prosody biases emotional verbal content processing, even when conflicting with verbal content and face simultaneously. Implications for multimodal communication and language evolution studies are discussed.

Humans identify negative (but not positive) arousal in silver fox vocalizations: implications for the adaptive value of interspecific eavesdropping.

The ability to identify emotional arousal in heterospecific vocalizations may facilitate behaviors that increase survival opportunities. Crucially, this ability may orient inter-species interactions, particularly between humans and other species. Research shows that humans identify emotional arousal in vocalizations across multiple species, such as cats, dogs, and piglets. However, no previous study has addressed humans' ability to identify emotional arousal in silver foxes. Here, we adopted low- and high-arousal calls emitted by three strains of silver fox-Tame, Aggressive, and Unselected-in response to human approach. Tame and Aggressive foxes are genetically selected for friendly and attacking behaviors toward humans, respectively. Unselected foxes show aggressive and fearful behaviors toward humans. These three strains show similar levels of emotional arousal, but different levels of emotional valence in relation to humans. This emotional information is reflected in the acoustic features of the calls. Our data suggest that humans can identify high-arousal calls of Aggressive and Unselected foxes, but not of Tame foxes. Further analyses revealed that, although within each strain different acoustic parameters affect human accuracy in identifying high-arousal calls, spectral center of gravity, harmonic-to-noise ratio, and F0 best predict humans' ability to discriminate high-arousal calls across all strains. Furthermore, we identified in spectral center of gravity and F0 the best predictors for humans' absolute ratings of arousal in each call. Implications for research on the adaptive value of inter-specific eavesdropping are discussed.

How small could a pup sound? The physical bases of signaling body size in harbor seals.

Vocal communication is a crucial aspect of animal behavior. The mechanism which most mammals use to vocalize relies on three anatomical components. First, air overpressure is generated inside the lower vocal tract. Second, as the airstream goes through the glottis, sound is produced via vocal fold vibration. Third, this sound is further filtered by the geometry and length of the upper vocal tract. Evidence from mammalian anatomy and bioacoustics suggests that some of these three components may covary with an animal's body size. The framework provided by acoustic allometry suggests that, because vocal tract length (VTL) is more strongly constrained by the growth of the body than vocal fold length (VFL), VTL generates more reliable acoustic cues to an animal's size. This hypothesis is often tested acoustically but rarely anatomically, especially in pinnipeds. Here, we test the anatomical bases of the acoustic allometry hypothesis in harbor seal pups Phoca vitulina. We dissected and measured vocal tract, vocal folds, and other anatomical features of 15 harbor seals post-mortem. We found that, while VTL correlates with body size, VFL does not. This suggests that, while body growth puts anatomical constraints on how vocalizations are filtered by harbor seals' vocal tract, no such constraints appear to exist on vocal folds, at least during puppyhood. It is particularly interesting to find anatomical constraints on harbor seals' vocal tracts, the same anatomical region partially enabling pups to produce individually distinctive vocalizations.

Monkey vocal tracts are speech-ready.

For four decades, the inability of nonhuman primates to produce human speech sounds has been claimed to stem from limitations in their vocal tract anatomy, a conclusion based on plaster casts made from the vocal tract of a monkey cadaver. We used x-ray videos to quantify vocal tract dynamics in living macaques during vocalization, facial displays, and feeding. We demonstrate that the macaque vocal tract could easily produce an adequate range of speech sounds to support spoken language, showing that previous techniques based on postmortem samples drastically underestimated primate vocal capabilities. Our findings imply that the evolution of human speech capabilities required neural changes rather than modifications of vocal anatomy. Macaques have a speech-ready vocal tract but lack a speech-ready brain to control it.

Seeking Temporal Predictability in Speech: Comparing Statistical Approaches on 18 World Languages.

Temporal regularities in speech, such as interdependencies in the timing of speech events, are thought to scaffold early acquisition of the building blocks in speech. By providing on-line clues to the location and duration of upcoming syllables, temporal structure may aid segmentation and clustering of continuous speech into separable units. This hypothesis tacitly assumes that learners exploit predictability in the temporal structure of speech. Existing measures of speech timing tend to focus on first-order regularities among adjacent units, and are overly sensitive to idiosyncrasies in the data they describe. Here, we compare several statistical methods on a sample of 18 languages, testing whether syllable occurrence is predictable over time. Rather than looking for differences between languages, we aim to find across languages (using clearly defined acoustic, rather than orthographic, measures), temporal predictability in the speech signal which could be exploited by a language learner. First, we analyse distributional regularities using two novel techniques: a Bayesian ideal learner analysis, and a simple distributional measure. Second, we model higher-order temporal structure-regularities arising in an ordered series of syllable timings-testing the hypothesis that non-adjacent temporal structures may explain the gap between subjectively-perceived temporal regularities, and the absence of universally-accepted lower-order objective measures. Together, our analyses provide limited evidence for predictability at different time scales, though higher-order predictability is difficult to reliably infer. We conclude that temporal predictability in speech may well arise from a combination of individually weak perceptual cues at multiple structural levels, but is challenging to pinpoint.

What Pinnipeds Have to Say about Human Speech, Music, and the Evolution of Rhythm.

Research on the evolution of human speech and music benefits from hypotheses and data generated in a number of disciplines. The purpose of this article is to illustrate the high relevance of pinniped research for the study of speech, musical rhythm, and their origins, bridging and complementing current research on primates and birds. We briefly discuss speech, vocal learning, and rhythm from an evolutionary and comparative perspective. We review the current state of the art on pinniped communication and behavior relevant to the evolution of human speech and music, showing interesting parallels to hypotheses on rhythmic behavior in early hominids. We suggest future research directions in terms of species to test and empirical data needed.