How Behavior Spreads

Social contagions include ideas and behaviors.

The spread, or diffusion, of social contagions occurs through social networks. Conventional wisdom about how this occurs proves fundamentally wrong.

Consider how 1960s Korea dealt with runaway population growth. The Korean government sought to slow it through social influence via peer networks. Koreans in villages and towns gently diffused information about contraception to neighbors and close friends. These clusters of close ties overlapped, so that gradually, everyone in a village would get the message from a trusted peer.

Most theorists and students of social networking assume that ideas spread through society quickly and efficiently along weak ties – people who loosely associate with each other. This works well for simple ideas and information – and for highly transmissible diseases – but not when involving a potential contagion of complex ideas, a new technology adoption or a substantive behavior change. 

Weak ties in networks may slow the spread of innovation and behavior change.

Dangerous and detrimental contagions often spread despite efforts to contain...