Fig. 2.

Direct and total effects of a behavioural change intervention with the assumption that the probability of change is high except in people most resistant to change, by target group

Note: The total effect of the intervention is the sum of its direct and indirect effects. People’s responses to the intervention are affected by their pre-existing attitudes, specifically by how resistant or amenable they are to the new behaviour. For this figure, it was assumed that the probability of behaviour change on exposure to the intervention was relatively high for all but the most resistant. The target group comprises the type of individuals who would initially be targeted by the intervention. For example, if the target size is 50% and the target group comprises resistant individuals, the 50% of the population with the highest resistance (based on their attitudes) is targeted. More details are available from the data repository.²³