You Are Not So Smart: Why You Have Too Many Friends on Facebook, Why Your Memory Is Mostly Fiction, and 46 Other Ways You're Deluding Yourself

by David McRaney

To thrive, you know you need allies. You get a better picture of the world when you can receive information from multiple sources. You need friends because outcasts are cut off from valuable resources. So when you are around others, you look for cues as to how to behave, and you use the information offered by your peers to make better decisions.