By: Amanda cosgriff
The Social Brain Hypothesis
The Social Brain Hypothesis, stemmed from the ‘Machiavellian Intelligence Hypothesis,’ which first suggested the belief that primates differentiated from other species due to the need to understand their society (Dunbar & Shultz, 2007). The Social Brain Hypothesis (Dunbar & Shultz, 2007), is the most favored theory that has been developed to help explain the differences in brain size across species. For example, why the human brain is larger than the primate brain (van Schaik, Isler, & Burkart, 2012). Dunbar & Shultz (2007) suggested the size of a specie’s brain relies on the stability of a social group and type and quality of relationships result in larger neocortices compared to individuals who have unstable and isolated social lives.
The concept behind why the brain grows and adapts is difficult to concretely define. It is one of the most taxing research questions for researchers as to why the human brain is the largest in size. The brain has evolved significantly since the evolution of the first human to humans living in the year 2017. It could be argued humans need larger brains in order to adapt and to and maintain the understanding of all the rapid technological advances, and nuances of understanding technological-social cues. Previous research has reported a correlation exists between the size of an individual’s brain and the size of their social networking system (von Der Heide, Vyas, & Olson, 2014). Results from this study indicate that there are specific regions in the brain that respond to associations between a face and information corresponding to that face.
The ability to keep up with and maintain intimate and personal relationships comes with the use of a lot of brain energy (Dunbar & Shultz, 2007). Choosing the ‘right’ individual in hopes to spend the rest of your life with them can be a taxing and complicated task compared to having multiple relationships. In fact, research has suggested organisms that engage in polygamous relationships have smaller brains compared to organisms that are monogamous (Dunbar & Shultz, 2007). It can be argued organisms in monogamous relationships require more energy and a larger brain because they have to work at reading and understanding appropriate verbal and/or non-verbal communication as well as work on maintaining a working relationship.
The “Rebuttal”
Although the Social Brain Hypothesis is a widely accepted theory, it does not explain away everything. For example, not all species who have complex social relationships have brains similar in size to humans, nor can we assume that large and large brained animals have complex social lives. The SBH does not provide enough solid evidence indicating the SBH explains size difference in animals. For example, lemurs, as described in the van Schaik, Isler and Burkart (2012) article, have similar social relationships as primates but have smaller brains. This could be because different species require certain adaptive skills in order to maintain survival. For example, orangutans primarily live in the trees where there is not a high risk of predators compared to those of lemurs. One can argue against the SBH by using the “is it the chicken, or the egg?” debate. Did primates learn to climb in trees because they all discussed it amongst each other and decided to pass the information down, or did evolution take place and they learned climbing trees resulted in living.
Additionally, the SBH does not explain why species have the ability to adapt and enhance skills of general intelligence. It is believed these skills are acquired based off social learning. However, the ability to adapt and change the behavior based on an experience is better explained by having behavioral flexibility (Holekamp, 2006). It also can be argued it is not the individual’s ability to adapt, but rather the need to adapt to something in order to survive. The species learns through trial and error that some things work and do not work.
Although the SBH is the most widely accepted theory for explaining why humans have the largest neocortex, is not a perfect theory or explanation describing why humans have larger neocortices. The SBH focuses on the concept of the social life, whereas other theories discuss evolution, culture, and behavior.
- Dunbar, R.I.M, & Shultz, S. (2007). Evolution in the social brain. Science, 317, 1344-1347.
- Holekamp, K. E. (2006). Questioning the social intelligence hypothesis. TRENDS in Cognitive Sciences, 11(2), 66-69.
- van Schaik, C. P., Isler, K., & Burkart, J. M. Explaining brain size variation” from social to cultural brain. Trends in Cognitive Sciences, 16(5), 277-283.
- von Der Heide, R., & Vyas, G., & Olson, I. R. (2014). The social network-network: size is predicted by brain structure and function in the amygdala and paralimbic regions. Oxford University Press, 9, 1962-1972.