Sunday, December 19, 2004

Neocortex ratio

I'm reading a book called the The Tipping Point, by Malcolm Gladwell, who's basic premise is that ideas, behaviours, and products spread through social networks like viruses.

One of the interesting facts brought up in this book concerns the 'Neocortex Ratio', defined as the ratio of neocortex volume to the volume of the rest of the brain (i.e. total brain volume minus neocortex).

With a neocortex volume of 1006.5 cc and a total brain volume of 1251.8 cc (Stephan et al 1981), the neocortex ratio for humans is CR=4.1. This is about 50% larger than the maximum value for any other primate species (see Dunbar 1992a).

Dunbar believes that the neocortex ratio in primates is related to the size of their social groups and that intelligence evolved as a response to dealing with more complex social interactions. Dunbar found that the maximum effective social group size for humans is about 150. Several examples are cited, including the size of villages in hunter-gatherer societies, Amish villages, and military structures.

I think my neocortex ratio must be a little less than 4.1 based on my social group size. Hopefully I'm a little smarter (and more social) than the average gorilla. I predict if someone comes up with a non-invasive way to measure neocortex ratio, smart guys will pay big bucks to get sized up. Think about it...this could revolutionize the entire nerd dating scene. Instead of feeling inadequate about coming up short of the average 6, they could feel great about pulling out a studly 4.5.