The idea of social rejection has really become part of an ongoing conversation around things like school shooters in the US or lone wolves. We have a fundamental need to belong just as we have needs for food and water, she says. Some groups matter more to us than others based on what we personally value about ourselves,. And it also comes down to whether we like people, yes, but whether we see our groups and the groups that maybe we're not part of as an opportunity for social mobility.