H omo sapiens is an intensely gregarious species. This book is about the ways that mental life and social life interact and influence each other. The sophisticated ability of human beings to engage in highly complex and finely regulated interpersonal behaviors is probably one of the cornerstones of the evolutionary success of our species and the foundation of the increasingly complex forms of social organization that our species has been able to develop. According to the “social brain” hypothesis, it was evolutionary pressures and the cognitive demands of managing increasingly large and ever-more complex social groups that drove the development of the human brain, that most amazing computational
organ (Dunbar, 2007). The astounding development of humans’ mental and cognitive abilities and their impressive record of achievements are intimately tied to the interpersonal demands of coordinating increasingly large social groups. In fact, we might argue that social thinking and interpersonal behavior are in a symbiotic relation: It is the demands of social life that drive sophisticated mental strategies, and social thinking is the necessary prerequisite for effective social interaction (Forgas, 1981; Sedikides, Schopler, & Insko, 1998). Interpersonal behavior is also the essential “glue” that holds families, groups, and even whole societies together.