How many Facebook friends do you have?

Pleased that you have 400 close friends on Facebook? Sad that you only have 51? Well according to evolutionary anthropologist Robin Dunbar we can only have about 150 meaningful relationships at most: our brains aren't big enough for more. The number was derived by comparing the size of groups that species live in with the size of the brain and then extrapolating to humans. Interestingly enough, some recent neuroscience points to a correlation between the size of the amygdala and people's gregariousness. The amygdala's importance for emotion and fear in humans is well known but it turns out that the bigger it is the more outgoing you are. It's a correlation only of course.

Your friends can make you fat

In this morning's journal club we discussed Fowler and Christakis's "Dynamic spread of happiness in a large social network: A longtiudinal analysis over 20 years in the Framingham Heart Study". The authors are American doctors working in the field of medicine, public health and political science. Their work makes use of the Framingham Heart Study to analyse family and friendship ties, diet, lifestyle and a sense of well-being and have demonstrated that these behaviours and moods can spread through social networks similar to viruses. Obesity tends to spread through same-sex friendships. Starting and stopping smoking is more contagious than obesity and spreads across both sexes while the transmission of happiness tends to involve face-to-face happiness. Their new book is called Connected.

Some Links

1. It's not your peers, and it's not your friends: Some progress toward understanding the educational peer effect mechanism

2. Econometric Methods for Causal Evaluation of Education Policies and Practices:
A Non-Technical Guide

3. Denis the Dentist: people disproportionately choose careers whose labels resemble their names

4. http://www.babynamewizard.com/

5. Penelope Trunk: Brazen Careerist

6. Randomness, Luck, and other Situational Sources of Success and Failure

7. Why jobs obtained through networks may lower your earnings

8. Vive la Révolution!: Long term returns of 1968 to the angry students

9. Simultaneous behaviour: during the Winter Olympics in Edmonton (Canada) (HT: Eoin Rouine)

Finding Balloons

This has run for the last few days. Fascinating project funded by US defence department. Offered a cash prize to find 10 weather balloons hidden in undisclosed locations in the US. Took an MIT team 9 hours to do it using a simple incentive package they devised (described by Tyler Cowen here )