Social Neuroscience

Social neuroscience is the study of the associations between social and neural levels of analysis and the biological mechanisms underlying these associations. Neuroscientists have tended to focus on single organisms, organs, cells, or intracellular processes. Social species create relationships and organizations beyond the individual, however, and these emergent structures evolved hand in hand with neural and hormonal mechanisms to support them because the consequent social behaviors helped animals survive, reproduce, and care for offspring sufficiently long that they too reproduced. Human relationships represent a particularly important social structure that serves these functions. Social neuroscience is concerned with how biological systems implement social processes and behavior, capitalizing on concepts and methods from the neurosciences to inform and refine theories of social-psychological processes, and using social and behavioral concepts and data to inform and refine theories of neural organization and function.

Consider the recent evolutionary development of the brain, which has grown substantially larger than needed to maintain life. According to the social brain hypothesis, deducing better ways to find food, avoid perils, and navigate territories has adaptive value for large mammals, but the complexities of these ecological demands pale by comparison to the complexities of social living. The latter include (a) learning by social observation; (b) recognizing the shifting status of friends and foes; (c) anticipating and coordinating efforts between two or more individuals; (d) using language to communicate, reason, teach, and deceive others; (e) orchestrating relationships, ranging from pair bonds and families to friends, bands, and coalitions; (f) navigating complex social hierarchies, social norms, and cultural developments; (g) subjugating self-interests to the interests of the pair bond or social group in exchange for the possibility of long-term benefits; (h) recruiting support to sanction individuals who violate group norms; and (i) doing all this across time frames that stretch from the distant passt to multiple possible futures. Accordingly, cross-species comparisons suggest that the evolution of large and metabolically expensive [Page 1553]brains is more closely associated with social than ecological complexity, at least in primates.

Even within anthropoid primates, the achievements of Homo sapiens are notable. Humans were not the first bipedal creatures or the first to use tools, but humans, apparently uniquely, contemplate the history of the earth, the reach of the universe, the origin of the species, and the genetic blueprint of life. Estimates among biologists at the dawn of the 21st century were that 100,000 genes were needed for the cellular processes that are responsible for complex human behavior. It appears that humans have only about a quarter this number of genes, but as a species we have been faster than other animals to acquire new genes and to discard unnecessary ones. The frontal cortex is particularly important for critical behaviors such as executive function and working memory, yet the ratio of frontal to total cortical gray matter is about the same in humans as in nonhuman primates. Although humans may have more cortical neurons than other mammals, whales and elephants are not far behind on this count. The specialized capacities of humans may depend less on the number of neurons than the number of synapses in the brain, the greater cell-packing density in the brain, and the higher neural conduction velocities, which together raise the overall capacity for abstraction, representation, and information processing.

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