Evolution of the Social Brain BY CASEY WATERS

What makes us different from chimpanzees? Social intelligence Sense of self Theory of Mind Our brains have evolved under social pressures to make us self-aware individuals who define ourselves by what we share with our group Our brains are 3 x larger than chimp brains Increased neocortex size

Sense of Self Structures in the human brain that suggest more complex systems of experiencing emotion Our amygdalae are significantly larger Insula- responsible for integrating emotion and bodily sensation Thalamus > posterior insula > anterior insula Global emotional awareness of bodily homeostasis Salient self implies self-awareness

Sense of Self In humans, insula uniquely responds to music and language Learned social dimension of salient self Insula activation in social exclusion and inequality Our brains expect social equality in group membership How does this play into our hunter-gatherer history?

Who is Robin* Dunbar? British anthropologist and evolutionary psychologist Proposed the Social Brain Hypothesis Also famous formulating Dunbar’s number

Social Brain Hypothesis Primates evolved larger brains to survive and reproduce in intricate social systems Increased neocortex size Initially coined the “Machiavellian intelligence hypothesis” Response to Jerison (1973) assumption that human intelligence evolved to deal with ecological problem solving

Social Brain Hypothesis Because our brains are “expensive”, difficult to justify need for larger brains to do the same ecological jobs as other species Steep cost gradient Human brain consumes 20% of total energy, while our brains weigh about 2 lbs. Considering the average human weighs 150 lbs. , the brain is only 1. 3% of total body weight.

Social Brain Hypothesis Language may have arisen as a “cheap” means of social grooming Social grooming consists of bonding practices, reinforcing social structure, and sometimes reconciliation Without language, humans would have to spend nearly half of their time on social grooming

Dunbar’s Number Suggested cognitive limit to number of individuals one person can maintain social relationships with 150 is the magic number Can fluctuate between 100 -250 people Numbers larger than this require more restrictive rules and norms to maintain stability Facebook?

Chimpanzee Theory of Mind- ability to reason about mental states Chimps incapable of symbolic behavior, language, and culture Can pass on learned behaviors, can’t pass on world views No understanding of false beliefs

Some rudimentary traits of social intelligence exist in chimps: Deception Understanding Social perception and intention learning Trading and roles Cooperation Altruism

Intentionality Dates back to medieval philosophy and adopted by Edmund Husserl Intentionality- quality of mental states (e. g. , thoughts, beliefs, desires, hopes) being directed toward some object or state of affairs Dunbar states chimps may aspire to around 1. 5 order of intentionality Humans in most situations operate around 3 rd order of intentionality 6 th order exceptionally difficult No concrete limit to intentionality, simply limited to our cognitive capacity as humans

Intentionality No intentionality: Having knowledge, but no awareness of knowledge. First Order: Holding a belief system aside from mere knowledge. Second Order: Awareness of your belief system; this is Theory of Mind. Children of 4 years of age and some apes operate at this order. Third Order: Holds communicative intent. Communicating internal intentions or beliefs to others so there is common ground for communication. Fourth Order: Awareness of a communicative act distinct from the communicative act itself. Story telling or story understanding capability. Fifth Order: Awareness of roles and narratives distinct from the role or narrative. Can be cultures or worldviews. Dunbar considers religion and storytelling at this level.

Intentionality Less than 20% of humans are able to operate on 6 th level of intentionality. Shakespearian literature For Shakespeare to write stories on the 5 th level, he had to be operating at the 6 th level of intentionality.

What makes us human? Conclusion and thoughts We are more socially intelligent in comparison to chimps, but Rudimentary capabilities of social intelligence and a limited Theory of Mind in chimps.