Why are people so strongly motivated to have relationships? According to a landmark paper by psychologists Roy Baumeister and Mark Leary it’s because of a fundamental “need to belong.”1 The “belongingness hypothesis” states that people have a basic psychological need to feel closely connected to others, and that caring, affectionate bonds from close relationships are a major part of human behavior.

Here is an overview of the evidence for this hypothesis, point by point:

1. Forming social bonds – People readily form relationships with others without being paid or forced to do so, and do so even under adverse circumstances. For example, infants and children will form attachments to others even though they have little or no knowledge of their social world and are incapable of calculating benefits or costs to these relationships.

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