Network models of diffusion predominantly think about cultural variation as a product of social contagion. But culture does not spread like a virus. In this paper, we propose an alternative explanation which we refer to as associative diffusion. Drawing on two insights from research in cognition—that meaning inheres in cognitive associations between concepts, and that such perceived associations constrain people’s actions—we propose a model wherein, rather than beliefs or behaviors per-se, the things being transmitted between individuals are perceptions about what beliefs or behaviors are compatible with one another. Conventional contagion models require an assumption of network segregation to explain cultural variation. In contrast, we demonstrate that the endogenous emergence of cultural differentiation can be entirely attributable to social cognition and does not necessitate a clustered social network or a preexisting division into groups. Moreover, we show that prevailing assumptions about the effects of network topology do not hold when diffusion is associative.