The metabolic expense of producing and operating neural tissue required for adaptive behaviour is considered a significant selective force in brain evolution. In primates, brain size correlates positively with group size, presumably owing to the greater cognitive demands of complex social relationships in large societies. Social complexity in eusocial insects is also associated with large groups, as well as collective intelligence and division of labour among sterile workers. However, superorganism phenotypes may lower cognitive demands on behaviourally specialized workers resulting in selection for decreased brain size and/or energetic costs of brain metabolism. To test this hypothesis, we compared brain investment patterns and cytochrome oxidase (COX) activity, a proxy for ATP usage, in two ant species contrasting in social organization. Socially complex Oecophylla smaragdina workers had larger brain size and relative investment in the mushroom bodies (MBs)-higher order sensory processing compartments-than the more socially basic Formica subsericea workers. Oecophylla smaragdina workers, however, had reduced COX activity in the MBs. Our results suggest that as in primates, ant group size is associated with large brain size. The elevated costs of investment in metabolically expensive brain tissue in the socially complex O. smaragdina, however, appear to be offset by decreased energetic costs.

Loneliness, or the perceived discrepancy of ones relationships in terms of quality, is known as Perceived Social Isolation (PSI). Studies have shown that PSI is both increasing and is correlated with health risks. Specifically, PSI is not only related with risks of mortality but is also linked with variations in the brain. Having few social contacts, or being Objectively Socially Isolated (OSI) does not qualify as PSI. The aim of this thesis is to investigate the neural correlates of PSI, as distinguished from OSI. The true role of PSI is still unknown, however, arguments can be made that PSI serves an important role in survival. The social brain, which allows for social cognition is used as a basis for understanding PSI in this thesis. In this thesis, I found that individuals suffering from PSI have increased attention towards social threat, and a preference to engage in positive social stimuli. Further, PSI affects both social cognition and the social brain. However, regional brain activity was not confined to the social brain. The results showed that PSI may be related to both affective and attentional networks of the brain. PSI also affects activity in the ventral striatum. Further, PSI is related to varied regional brain size. I argue that PSI can be reduced by mainly fixing maladaptive cognitive patterns.

The past decade has witnessed a proliferation of internet use for socialising with dedicated websites such as Facebook, and also for maintaining relationships using computer mediated communication. Individuals can extend the boundary associated with traditional forms of communication, and use technology to meet strangers online to share interests, or maintain existing relationships remotely. One of the most significant functions of computer-mediated communication (CMC) is its contribution to the evolution of social communication. CMC is “communication that takes place between human beings via the instrumentality of computers” (Thurlow, Lengel, & Tomic, 2004). As a consequence of the convenience and flexibility that this channel provides, CMC can be effectively used to orchestrate a variety of communication situations. Furthermore, social networks sites are becoming the choice in which individuals are maintaining relationships or meeting new people. The potential distinctions between these relationships and their offline counterparts remain contradictory. Online relationships may face different challenges, such as anonymity, restricted interaction (Walther, 1992), and the lack of physical presence. For example, sharing activities online such as playing games or visiting Web sites together differs from offline activities, such as going to the movies or dining together. These observations question whether CMC relationships have any parallels with real world relationships. Dunbar (1992) structured real world relationship by strength of ties and formulated the social brain hypothesis (SBH). This work uses the SBH as an interpretive lens in analyzing CMC relationship ties. Thus, a major focus of this work is to investigate implications of the SBH (Dunbar, 1992) within the context of CMC usage. It is recognised that CMC allows for the maintenance of a large number of friendships. Thus potentially, the use of CMC could alter the SBH ratios. Within the main findings consistency with SBH was found. Furthermore, CMC has many parallels with real world communication methods. Face-to-face communications were strongly preferred for maintenance of strong ties. Also phone usage was analysed and identified as an indicator of strong tie relationships, for both local and distant communications. The findings also address questions on displaced communities communication habits and their use of CMC. The phone was found to be most popular media and culture had a strong influence on communication content. The research used a mixed method approach, combining data collection via questionnaires, semi structured interviews and a diary study completed by participants. Based on the findings, a framework is proposed categorising groups on their level of real world socialising and CMC use. There are four essential contributions impacting on current theory. The findings offer new knowledge within the research of CMC and relationship maintenance theory. In our understanding these exploratory questions have not yet been addressed and therefore the findings of this research project are significant in their contributions.

The social brain hypothesis predicts that larger group size and greater social complexity select for increased brain size. In ants, social complexity is associated with large colony size, emergent collective action, and division of labor among workers. The great diversity of social organization in ants offers numerous systems to test social brain theory and examine the neurobiology of social behavior. My studies focused on the Australasian weaver ant, Oecophylla smaragdina, a polymorphic species, as a model of advanced social organization. I critically analyzed how biogenic amines modulate social behavior in ants and examined their role in worker subcaste-related territorial aggression. Major workers that naturally engage in territorial defense showed higher levels of brain octopamine in comparison to more docile, smaller minor workers, whose social role is nursing. Through pharmacological manipulations of octopaminergic action in both subcastes, octopamine was found to be both necessary and sufficient for aggression, suggesting subcaste-related task specialization results from neuromodulation. Additionally, I tested social brain theory by contrasting the neurobiological correlates of social organization in a phylogenetically closely related ant species, Formica subsericea, which is more basic in social structure. Specifically, I compared brain neuroanatomy and neurometabolism in respect to the neuroecology and degree of social complexity of O. smaragdina major and minor workers and F. subsericea monomorphic workers. Increased brain production costs were found in both O. smaragdina subcastes, and the collective action of O. smaragdina majors appeared to compensate for these elevated costs through decreased ATP usage, measured from cytochrome oxidase activity, an endogenous marker of neurometabolism. Macroscopic and cellular neuroanatomical analyses of brain development showed that higher-order sensory processing regions in workers of O. smaragdina, but not F. subsericea, had age-related synaptic reorganization and increased volume. Supporting the social brain hypothesis, ecological and social challenges associated with large colony size were found to contribute to increased brain size. I conclude that division of labor and collective action, among other components of social complexity, may drive the evolution of brain structure and function in compensatory ways by generating anatomically and metabolically plastic mosaic brains that adaptively reflect cognitive demands of worker task specialization and colony-level social organization.

Adolescence is an exceptional period of life, not least in terms of social and brain development. Friends become increasingly important, susceptibility to peer rejection increases, and brain regions involved in social cognition are predicted to go through major changes. Adolescents’ social lives today may, to different extents, take place on social-media platforms online. This systematic review investigates how social-media use (SMU) affects adolescents’ brains. Out of 626 studies from the initial search, seven met the inclusion criteria. Out of these, five studies used functional magnetic resonance imaging, one study used diffusion tensor imaging, and one study used diffusion-weighted imaging. Functional findings suggest the reward circuit of the brain, as well as brain regions implicated in social cognition, to be involved in SMU. Activity in the nucleus accumbens was elicited by both giving and getting likes on posted pictures, whereas more SMU related to increased activity in the medial prefrontal cortex during physical self-judgement. Structural findings indicate frequent SMU to be associated with more reward sensitivity in terms of increased white matter in reward-processing pathways. These studies provide an initial understanding of the neural mechanisms of adolescents’ SMU. Future research is needed to draw inferences about how SMU affects the brains of adolescents.

What selective forces and molecular mechanisms govern the integration of worker body size and morphology, brain architecture, and behavior in insect societies? Workers of the remarkably polyphenic and socially complex fungus-growing leafcutter ant Atta cephalotes exhibit a striking agricultural division of labor. The number of morphologically distinct and behaviorally differentiated worker groups, adaptive mosaic neural phenotypes, and brain transcriptomes have not been examined and the influences of socioecological challenges on behavioral performance, cognition, and brain evolution are unclear. We quantified worker morphological and behavioral variation to assess the number of worker size classes and characterized their social roles. We discriminated multiple worker size groups using a Gaussian mixture model: mid-sized workers (“medias”) had the most diverse task repertories and serve dominant roles in leaf harvesting, whereas workers of other size classes performed fewer, more specialized behaviors. We used variation among tasks in sensorimotor functions and task performance frequencies to create an estimate of sensory integration and processing demands across worker size groups. This metric predicted that medias require the greatest neural investment due to the high diversity of sensory inputs and motor functions associated with their task set. We quantified the volumes of key neuropils in brains of workers of different sizes and determined their allometries, finding that our estimate corresponded to proportional investment in the mushroom bodies, a brain compartment responsible for learning, memory, and sensory integration, and identifying allometric scaling patterns in other brain centers. Additionally, we measured whole-brain gene expression and identified significant differences in expression levels for numerous genes likely to underpin behavior. Differences were most pronounced between the smallest (fungal gardener “minims”) and largest (defensive “majors”), although not all expression differences were driven by worker size. Overrepresented gene functional categories included those related to sensory processing (enriched in genes upregulated in medias and minims) and metabolism (enriched in genes upregulated in majors). These results identify the nature of selective forces favoring differentiation along morphological, neuroanatomical, behavioral, and molecular axes among A. cephalotes workers and the impact of advanced division of labor on brain evolution. / 2023-03-01T00:00:00Z

À l’interface des neurosciences et de la psychologie sociale expérimentale, nos travaux explorent les bases neuronales de la « facilitation sociale » (effet facilitateur de la présence d’un congénère sur la performance) chez le singe à partir d'enregistrements électrophysiologiques unitaires dans le cortex préfrontal dorsolatéral et dans le cortex cingulaire antérieur. L'analyse de l’activité de 342 neurones liée au codage des résultats de l’action (signaux d'erreur et de succès) révèle que, dans leur grande majorité, les neurones de ces deux structures expriment une sensibilité différenciée à la présence du congénère. Trois populations de neurones sont découvertes: des neurones dits « sociaux », dont la décharge est plus ample en présence du congénère qu’en son absence, des neurones dits « asociaux », avec un pattern de décharge inverse, et une population plus minoritaire dite « neutre », dont l’amplitude de décharge est la même dans ces deux conditions. Il apparaît que les relations entre le comportement et l'activité neuronale lors du codage des signaux d’erreur dépendent de la nature plus ou moins compatible des populations neuronales identifiées avec les contextes de performance eux-mêmes. Nos résultats indiquent une implication majeure des neurones sociaux dans les effets de facilitation sociale étudiés depuis un siècle dans plusieurs espèces animales et offrent un nouveau regard sur le cerveau social. Sans nier l’idée de régions entières spécialisées dans le traitement des informations sociales, nos travaux suggèrent que des populations neuronales dotées d’une sensibilité plus ou moins sociale coexistent et probablement interagissent à l’échelle du cerveau entier. / At the interface of neuroscience and experimental social psychology, our work explores the neural bases of « social facilitation » (the facilitating effect of the presence of a conspecific on performance) in monkeys using single-unit electrophysiological recordings in the dorsolateral part of the prefrontal cortex (PFDL) and the anterior cingulate cortex (ACC). The analysis of the activity of 574 neurons coding for error signals and successes reveals that the vast majority of neurons in both structures express a differential sensitivity to social presence. Three populations of neurons are discovered : neurons called « social », exhibiting higher discharge rate in the presence of a conspecific than alone, neurons called « asocial », exhibiting a reverse discharge pattern, and neurons called « neutral », whose discharge magnitude is the same in both conditions. More importantly, it appears that the relationship between behavior and neural activity when encoding error feedback depends on whether the neuronal populations at stake are compatible or incompatible with the performance contexts themselves. Overall, our results indicate a major role of social neurons in social facilitation effects studied for a century in several animal species and offer a new look at the « social brain ». Without denying the idea of entire regions involved in the processing of social information, our work suggests that neuronal populations with varying degrees of social sensitivity actually coexist and probably interact across the whole brain.

Neste trabalho discuto sobre o senso comum, que é invariavelmente uma dimensão social do conhecimento, concebido na forma de crenças, conhecimentos, julgamentos e valores que são igualmente compartilhados por um conjunto de pessoas. Por isso, concepções sobre o senso comum estão presentes explicitamente em diferentes disciplinas, como as Ciências Humanas e a Inteligência Artificial, e implicitamente em alguns conceitos fundamentais como o de inteligência. Meu objetivo neste trabalho é representar o senso comum. A tática empregada para isso foi questionar as diferenças existentes no entendimento entre as partes envolvidas em situações de entendimento comum. Diante disso, defendo que concepções abstratas e sistemáticas sobre o senso comum não conseguem explicar como pode haver, em uma dada situação, diferenças existentes no entendimento comum nem entendimento comum em meio a diferenças existentes. Alternativamente, defendo que o senso comum acontece localmente, de maneira não garantida e não sistemática. Como as palavras e conceitos no início das interações são ambíguas, polissêmicas, lacunosas, etc. há a necessidade de estabelecer referências comuns para que seja possível o entendimento comum e manter relações sociais mais duradouras: a) essas relações têm restrições sobre o número de relações mais próximas segundo a hipótese do cérebro social, e b) essas referências estão baseadas na relação de analogias de outras experiências como um modo de entender situações novas. As relações podem ser representadas na forma de redes sociais, enquanto as referências podem ser representadas por redes semânticas, nas quais a familiaridade do repertório pode ser tratada como o crescimento da rede total de referências de uma pessoa. Defendo que é possível conceber o paralelismo entre a rede social de uma pessoa e sua rede semântica geral, e esse paralelismo pode ser representado. / I discuss here the common sense, which is invariably a social dimension of knowledge, conceived in the form of beliefs, knowledge, judgments and values that are equally shared by a set of people. Hence, conceptions about common sense are explicitly present in different disciplines, such as the Human Sciences and Artificial Intelligence, and implicitly in some fundamental concepts such as intelligence. My goal here is to represent common sense. For that, I question the differences existing in the understanding between people involved in situations of common understanding. Therefore, I argue that abstract and systematic conceptions of common sense cannot explain how there can be \"differences in the common understanding\" or \"common understanding in the midst of existing differences\" in a given situation. Alternatively, I argue that common sense happens locally, in a not taken-for-grated and unsystematic way. Since at the beginning interactions words and concepts are both ambiguous, polysemic, lacunose, etc. there is a need to establish common references so that common understanding can be possible and more lasting social relations can be maintained: a) relations have restrictions on the number of closer ones according to the social brain hypothesis, and b) references are based on the relation of analogies of other experiences as a way to understand new situations. Relationships can be represented in the form of social networks, while references can be represented by semantic networks in which repertory familiarity can be treated as the growth of a person\'s total network of references. I argue that it is possible to conceive the parallelism between a person\'s social network and its general semantic network, and this parallelism can be represented.

Neste trabalho discuto sobre o senso comum, que é invariavelmente uma dimensão social do conhecimento, concebido na forma de crenças, conhecimentos, julgamentos e valores que são igualmente compartilhados por um conjunto de pessoas. Por isso, concepções sobre o senso comum estão presentes explicitamente em diferentes disciplinas, como as Ciências Humanas e a Inteligência Artificial, e implicitamente em alguns conceitos fundamentais como o de inteligência. Meu objetivo neste trabalho é representar o senso comum. A tática empregada para isso foi questionar as diferenças existentes no entendimento entre as partes envolvidas em situações de entendimento comum. Diante disso, defendo que concepções abstratas e sistemáticas sobre o senso comum não conseguem explicar como pode haver, em uma dada situação, diferenças existentes no entendimento comum nem entendimento comum em meio a diferenças existentes. Alternativamente, defendo que o senso comum acontece localmente, de maneira não garantida e não sistemática. Como as palavras e conceitos no início das interações são ambíguas, polissêmicas, lacunosas, etc. há a necessidade de estabelecer referências comuns para que seja possível o entendimento comum e manter relações sociais mais duradouras: a) essas relações têm restrições sobre o número de relações mais próximas segundo a hipótese do cérebro social, e b) essas referências estão baseadas na relação de analogias de outras experiências como um modo de entender situações novas. As relações podem ser representadas na forma de redes sociais, enquanto as referências podem ser representadas por redes semânticas, nas quais a familiaridade do repertório pode ser tratada como o crescimento da rede total de referências de uma pessoa. Defendo que é possível conceber o paralelismo entre a rede social de uma pessoa e sua rede semântica geral, e esse paralelismo pode ser representado. / I discuss here the common sense, which is invariably a social dimension of knowledge, conceived in the form of beliefs, knowledge, judgments and values that are equally shared by a set of people. Hence, conceptions about common sense are explicitly present in different disciplines, such as the Human Sciences and Artificial Intelligence, and implicitly in some fundamental concepts such as intelligence. My goal here is to represent common sense. For that, I question the differences existing in the understanding between people involved in situations of common understanding. Therefore, I argue that abstract and systematic conceptions of common sense cannot explain how there can be \"differences in the common understanding\" or \"common understanding in the midst of existing differences\" in a given situation. Alternatively, I argue that common sense happens locally, in a not taken-for-grated and unsystematic way. Since at the beginning interactions words and concepts are both ambiguous, polysemic, lacunose, etc. there is a need to establish common references so that common understanding can be possible and more lasting social relations can be maintained: a) relations have restrictions on the number of closer ones according to the social brain hypothesis, and b) references are based on the relation of analogies of other experiences as a way to understand new situations. Relationships can be represented in the form of social networks, while references can be represented by semantic networks in which repertory familiarity can be treated as the growth of a person\'s total network of references. I argue that it is possible to conceive the parallelism between a person\'s social network and its general semantic network, and this parallelism can be represented.

The social brain hypothesis (SBH) posits that complex social environments exert a major selection pressure driving the evolution of large brains and intelligence. The hypothesis was first proposed to explain the remarkable cognitive abilities of primates and has since been extended to other vertebrate groups and gained a substantial popularity. Nevertheless, the empirical support is equivocal in virtually every group where the hypothesis has been tested. In this thesis, the SBH is tested in the African mole-rats (Bathyergidae). Mole-rats share a subterranean mode of life and similar ecologies while covering the whole social spectrum, from solitary to "eusocial". The number of brain neurons is considered a better proxy for intelligence than relative or absolute brain size. Therefore, a novel approach, the isotropic fractionator, was used to estimate the total number of neurons and other cells in five brain parts (olfactory bulbs, cerebral cortex, cerebellum, diencephalon and basal ganglia, brain stem) of eleven bathyergid species. This simultaneously allows for examining if and how mole-rats differ from other rodents with respect to brain cellular scaling rules. We found that, contrary to expectations, mole-rats generally conform to these rules, with a few exceptions. They tend to have higher...