If your friends are obese, your risk of obesity is 45 percent higher. ... If your friend's friends are obese, your risk of obesity is 25 percent higher. ... If your friend's friend's friend, someone you probably don't even know, is obese, your risk of obesity is 10 percent higher. It's only when you get to your friend's friend's friend's friends that there's no longer a relationship between that person's body size and your own body size.

Everyday interactions we have with other people are definitely contagious, in terms of happiness.

Realizing the ways in which we humans may have been inadvertently changing our genes for millennia provides a way for us to begin to think about the inevitable genetic revolution in medicine that is going to allow us to advertently change our genes over centuries and even decades.

My entire youth was spent with an incredibly ill parent... I don't think you can grow up that way and not be marked by that experience.

We are, first of all, not solitary creatures and second of all, we are deeply embedded in the lives of others. It's very easy to forget that and to engage in an atomistic fallacy - where we think that all we have to do is study the individual components of a system in order to understand the system. That's clearly not the case when it comes to social systems.

Social networks are these intricate things of beauty, and they're so elaborate and so complex and so ubiquitous that one has to ask what purpose they serve.

The social sciences offer equal promise for improving human welfare; our lives can be greatly improved through a deeper understanding of individual and collective behavior. But to realize this promise, the social sciences, like the natural sciences, need to match their institutional structures to today's intellectual challenges.