Sociability and Amygdale Size
It is quite a well known fact that the centrality and extent of social behavior within species varies widely in the animal kingdom. The source of this difference has not been resolutely identified until recent years, when a cross-specie study with primates has demonstrated a strong relationship between the degree of sociability within a primate specie and its individuals’ Amygdale size.
The Amygdale, to put simply, is the part of the brain that is responsible for an individual’s emotional and social interactions with the outside world. Namely, one’s amygdale dictates the extent of their ability to feel sympathy and empathy for others, as well as their success in discerning facial expressions and the emotional behavior of others. In addition, it has been long known that the size of a part of a brain is often a reliable indicator of how developed and frequently-used that section is: A larger amygdale is indicative to a more sociable person, one who may more easily maintain a complex system of social connections with others.
Of course, a specie’s inclination to socialization is not as much a matter of choice as it may be with individual humans, but rather an evolutionarily selected trait that contributes to that specie’s survival. Nonetheless, a 2011 Neuroscience study (link at bottom) has demonstrated a visible relationship between the degree of individual humans’ sociability and the size of their amygdale.
The study was conducted using 58 individuals, taken from all ages and self-identified racial groups. The conductors have evaluated each individual’s “sociability” using metrics that we have defined in class and in the textbook:
- The number of strong connections (regular contacts) that individual possesses – The significance of this measure is rather self-explanatory using the Triadic Closure Property that we have discussed in class: If an individual is able to consistently maintain a certain number of strong connections, it is a good indicator that they are capable of establishing new connections with their friends’ friends.
- The number of common connections that they maintain with their friends – In other words, the experiment conductors made use of the textbook-defined embeddedness of each individual’s connections to ascertain their sociability.
- The overall number of connections (positive or negative) that an individual possesses – As shown in class, it is up to the individual to sort out and balance their friend/foe web, a skill that draws from the degree of their amygdale’s development. If an individual cannot resolve uncomfortable social tensions such as two friends who compete for that individual’s attention and loyalty, it is not likely that either friend will remain in such a standby for long.
Based on this article’s findings, if one were to indicate each node’s amygdale size with its own size within a social network graph, it is easy to imagine how the largest circles (nodes) would be found bound to one another in large clusters, whereas smaller circles would more likely to be found in the periphery and the borders of those clusters.
It is quite interesting to correlate what has long been an intangible difference between sociability and its absence by the size of certain sections in the brain. The experimenter’s choice of how to quantify sociability made a fascinating connection between seemingly mundane quantities and measures that we have defined in class and the physical size of an individual’s amygdale.
http://www.nature.com/neuro/journal/v14/n2/full/nn.2724.html