Human Faces Are Slower than Chimpanzee Faces

BACKGROUND: While humans (like other primates) communicate with facial expressions, the evolution of speech added a new function to the facial muscles (facial expression muscles). The evolution of speech required the development of a coordinated action between visual (movement of the lips) and auditory signals in a rhythmic fashion to produce "visemes" (visual movements of the lips that correspond to specific sounds). Visemes depend upon facial muscles to regulate shape of the lips, which themselves act as speech articulators. This movement necessitates a more controlled, sustained muscle contraction than that produced during spontaneous facial expressions which occur rapidly and last only a short period of time. Recently, it was found that human tongue musculature contains a higher proportion of slow-twitch myosin fibers than in rhesus macaques, which is related to the slower, more controlled movements of the human tongue in the production of speech. Are there similar unique, evolutionary physiologic biases found in human facial musculature related to the evolution of speech?\ud \ud METHODOLOGY/PRINICIPAL FINDINGS: Using myosin immunohistochemistry, we tested the hypothesis that human facial musculature has a higher percentage of slow-twitch myosin fibers relative to chimpanzees (Pan troglodytes) and rhesus macaques (Macaca mulatta). We sampled the orbicularis oris and zygomaticus major muscles from three cadavers of each species and compared proportions of fiber-types. Results confirmed our hypothesis: humans had the highest proportion of slow-twitch myosin fibers while chimpanzees had the highest proportion of fast-twitch fibers.\ud \ud CONCLUSIONS/SIGNIFICANCE: These findings demonstrate that the human face is slower than that of rhesus macaques and our closest living relative, the chimpanzee. They also support the assertion that human facial musculature and speech co-evolved. Further, these results suggest a unique set of evolutionary selective pressures on human facial musculature to slow down while the function of this muscle group diverged from that of other primates.\ud \u

The Neuroscience of Understanding the Emotions of Others

We cannot help but impute emotions to the behaviors of others, and constantly infer not only what others are feeling, but also why they feel that way. The comprehension of other people’s emotional states is computationally complex and difficult, requiring the flexible, context-sensitive deployment of cognitive operations that encompass rapid orienting to, and recognition of, emotionally salient cues; classification of emotions into culturally-learned categories; and using an abstract theory of mind to reason about what caused the emotion, what future actions the person might be planning, and what we should do next in response. This review summarizes what neuroscience data − primarily functional neuroimaging data − has so far taught us about the cognitive architecture enabling emotion understanding in its various forms

The face is central to primate multicomponent signals

A wealth of experimental and observational evidence suggests that faces have become increasingly important in the communication system of primates over evolutionary time and that both the static and moveable aspects of faces convey considerable information. Therefore, whenever there is a visual component to any multicomponent signal the face is potentially relevant. However, the role of the face is not always considered in primate multicomponent communication research. We review the literature and make a case for greater focus on the face going forward. We propose that the face can be overlooked for two main reasons: first, due to methodological difficulty. Examination of multicomponent signals in primates is difficult, so scientists tend to examine a limited number of signals in combination. Detailed examination of the subtle and dynamic components of facial signals is particularly hard to achieve in studies of primates. Second, due to a common assumption that the face contains “emotional” content. A priori categorisation of facial behavior as “emotional” ignores the potentially communicative and predictive information present in the face that might contribute to signals. In short, we argue that the face is central to multicomponent signals (and also many multimodal signals) and suggest future directions for investigating this phenomenon

Top-down and bottom-up modulation in processing bimodal face/voice stimuli

<p>Abstract</p> <p>Background</p> <p>Processing of multimodal information is a critical capacity of the human brain, with classic studies showing bimodal stimulation either facilitating or interfering in perceptual processing. Comparing activity to congruent and incongruent bimodal stimuli can reveal sensory dominance in particular cognitive tasks.</p> <p>Results</p> <p>We investigated audiovisual interactions driven by stimulus properties (bottom-up influences) or by task (top-down influences) on congruent and incongruent simultaneously presented faces and voices while ERPs were recorded. Subjects performed gender categorisation, directing attention either to faces or to voices and also judged whether the face/voice stimuli were congruent in terms of gender. Behaviourally, the unattended modality affected processing in the attended modality: the disruption was greater for attended voices. ERPs revealed top-down modulations of early brain processing (30-100 ms) over unisensory cortices. No effects were found on N170 or VPP, but from 180-230 ms larger right frontal activity was seen for incongruent than congruent stimuli.</p> <p>Conclusions</p> <p>Our data demonstrates that in a gender categorisation task the processing of faces dominate over the processing of voices. Brain activity showed different modulation by top-down and bottom-up information. Top-down influences modulated early brain activity whereas bottom-up interactions occurred relatively late.</p

The language void: the need for multimodality in primate communication research

Theories of language evolution often draw heavily on comparative evidence of the communicative abilities of extant nonhuman primates (primates). Many theories have argued exclusively for a unimodal origin of language, usually gestural or vocal. Theories are often strengthened by research on primates that indicates the absence of certain linguistic precursors in the opposing communicative modality. However, a systematic review of the primate communication literature reveals that vocal, gestural and facial signals have attracted differing theoretical and methodological approaches, rendering cross-modal comparisons problematic. The validity of the theories based on such comparisons can therefore be questioned. We propose that these a priori biases, inherent in unimodal research, highlight the need for integrated multimodal research. By examining communicative signals in concert we can both avoid methodological discontinuities as well as better understand the phylogenetic precursors to human language as part of a multimodal system

A comparative developmental approach to multimodal communication in chimpanzees (Pan troglodytes)

Studying how communication of our closest relatives, the great-apes, develops can inform our understanding of the socio-ecological drivers shaping language evolution. However, despite a now recognized ability of great apes to produce multimodal signal combinations, a key feature of human language, we lack knowledge about when or how this ability manifests throughout ontogeny. In this thesis, I aimed to address this issue by examining the development of multimodal signal combinations (also referred to as multimodal combinations) in chimpanzees. To establish an ontogenetic trajectory of combinatorial signalling, my first empirical study examined age and context related variation in the production of multimodal combinations in relation to unimodal signals. Results showed that older individuals used multimodal combinations at significantly higher frequencies than younger individuals although the unimodal signalling remained dominant. In addition, I found a strong influence of playful and aggressive contexts on multimodal communication, supporting previous suggestions that combinations function to disambiguate messages in high-stakes interactions. Subsequently, I looked at influences in the social environment which may contribute to patterns of communication development. I turned first to the mother-infant relationship which characterises early infancy before moving onto interactive behaviour in the wider social environment and the role of multimodal combinations in communicative interactions. Results indicate that mothers support the development of communicative signalling in their infants, transitioning from more action-based to signalling behaviours with infant age. Furthermore, mothers responded more to communicative signals than physical actions overall, which may help young chimpanzees develop effective communication skills. Within the wider community, I found that interacting with a wider number of individuals positively influenced multimodal combination production. Moreover, in contrast to the literature surrounding unimodal signals, these multimodal signals appeared highly contextually specific. Finally, I found that within communicative interactions, young chimpanzees showed increasing awareness of recipient visual orientation with age, producing multimodal combinations most often when the holistic signal could be received. Moreover, multimodal combinations were more effective in soliciting recipient responses and satisfactory interactional outcomes irrespective of age. Overall, these findings highlight the relevance of studying ape communication development from a multimodal perspective and provide new evidence of developmental patterns that echo those seen in humans, while simultaneously highlighting important species differences. Multimodal communication development appears to be influenced by varying socio-environmental factors including the context and patterns of communicative interaction

Perceptual similarity: insights from crossmodal correspondences

Perceptual similarity is one of the most fiercely debated topics in the philosophy and psychology of perception. The documented history of the issue spans all the way from Plato – who regarded similarity as a key factor for human perceptual experience and cognition – through to contemporary psychologists – who have tried to determine whether, and if so, how similarity relationships can be established between stimuli both within and across the senses. Recent research on cross-sensory associations, otherwise known as crossmodal correspondences – that is, the existence of observable consensual associations, or mappings, between stimuli across different senses – represents an especially interesting field in which to study perceptual similarity. In fact, most accounts of crossmodal association that have been put forward in the literature to date evoke perceptual similarity as a key explanatory factor mediating the underlying association. At the same time, however, these various accounts raise several important theoretical questions concerning the very nature of similarity, with, for example, the sensory, affective, or cognitive underpinnings of similarity judgements remaining unclear. We attempt to shed light on these questions by examining the various accounts of crossmodal associations that have been put forward in the literature. Our suggestion is that perceptual similarity varies from being phenomenologically-based to conceptually-based. In particular, we propose that the nature of the associations underlying similarity judgements – whether these associations are phenomenologically-, structurally-, emotionally-, or conceptually-based – may be represented in a two-dimensional space with associative strength on one axis, and cognitive penetrability on the other

Las relaciones entre la mente, el territorio y la sociedad desde una perspectiva medio ambiental

In my view, there are four important aspects to EBS. 1. It needs to be seen as a scientific discipline dealing with EBS. It is highly interdisciplinary, involving many relevant disciplines. 2. Design involves the application of the latest and best established research findings. 3. To become a discipline, EBS must concentrate on building explanatory theory. 4. While an important function of theory is to provide unification and synthesis, conceptual unification, synthesis, conceptual development and generalization are also needed to begin to develop theory.Desde mi punto de vista, existen cuatro aspectos EBS (Environmental Behavioral Sciences) fundamentales en las ciencias que analizan las relaciones entre comportamiento y medio construido, o sea, en la relación entre la conducta y el lugar construido: 1. Es necesario considerarla como una disciplina científica, altamente interdisciplinar, por otro lado. 2. Proyectar estas relaciones (to design) exige conocer y aplicar los últimos y mejor consolidados resultados de esta disciplina. 3. Para llegar a ser una disciplina, las EBS deben explicar y teorizar sobre la construcción de espacios y de su impacto en el comportamiento social. 4. Aunque una función esencial de cualquier teoría sea unificar y sintetizar, también es preciso un desarrollo conceptual y una progresiva generalización cuando se empieza a construir una teoría nueva.Peer Reviewe