Social diffusion models

Innovations are diffused through social networks over time by well-established rules; health-related behaviours are no exception.

A body of social theory called social diffusion theory¹ has studied the diffusion of innovations in fields such as agriculture, international development and marketing. More than 4500 studies have been published on the diffusion of innovations.

Diffusion of innovations theory has been adopted for the study of the adoption of behaviour intended to avoid HIV infection. Diffusion theorists argue that a behaviour or innovation will be adopted if it is judged to have a high degree of utility, and if it is compatible with how individuals already think and act.

However, an innovation will only be considered if it is known about, and one of the major problems facing HIV educators is the difficulty of frank communication about HIV risk and how best to protect oneself and one's partners. The taboo status of much discussion about HIV makes it difficult for individuals to judge the utility of an innovation such as condom use, because frank discussion of condom use is impossible on television.

Diffusion research has also observed that innovations will tend to be adopted in a population according to a distribution that follows an S–shaped curve: that is, few at first, then an increasing proportion, and a few late adopters. Diffusion researchers have been very interested to define the characteristics of who adopts early, and who influences those who adopt an innovation later. They discovered that rates of adoption varied according to the homogeneity of the group, with innovations diffusing more rapidly in groups which were relatively homogenous. ‘Change agents’ who modelled a new innovation or disseminated information about it were most likely to be successful if they came from that group.

Two other factors cited as important in the diffusion of innovations have particular relevance to HIV prevention. ‘Testability’ – opportunities for individuals to experiment with an innovation – and ‘visibility’ – the knowledge that others are already doing it – are crucial steps in the diffusion process.