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

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.

I like to have met someone in real life before being their Facebook friend.

We will create life from inanimate compounds, and we will find life in space. But the life that should more immediately interest us lies between these extremes, in the middle range we all inhabit between our genes and our stars.

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.

One reason citizens, politicians and university donors sometimes lack confidence in the social sciences is that social scientists too often miss the chance to declare victory and move on to new frontiers.

Social media and the Internet haven't changed our capacity for social interaction any more than the Internet has changed our ability to be in love or our basic propensity to violence, because those are such fundamental human attributes.