‘Being green is worthless if others are not’: the effect of descriptive norms on pro-environmental behaviour is mediated by outcome expectancy / ‘Ser verde no vale de nada si los demás no lo son’: el efecto de las normas descriptivas sobre el comportamiento proambiental está mediado por la expectativa de resultado

Abstract

Descriptive norm effect has been explained in terms of either normative or informative social influence. This research investigates another possible mechanism in the case of collective goals. Because changing one’s behaviour — e.g., to protect the environment — will be effective only if other people also change their behaviour, their number will influence the outcome expectancy for that behaviour. Hence, we postulated that the effect of descriptive norm on adoption of a pro-environmental behaviour is mediated by outcome expectancy. Two studies showed that outcome expectancy mediated the effect of descriptive norm on intention to buy an energy-efficient refrigerator only in the case of a collective goal (vs. an individual goal) (Study 1, N = 787), and that the effect of descriptive norm on intention (with respect to a collective goal) can be reversed if an optimal uptake rate is mentioned, this interaction being mediated by outcome expectancy (Study 2, N = 400). These results suggest that the effect of descriptive norm, classically found in studies of pro-environmental behaviours, occurs because it gives people a sense that their action will have an impact.