Understanding the influence of individual behaviour and social networks in sustainability transitions.

Abstract

A behaviour change towards sustainable food purchasing behaviour is crucially necessary for the survival of the planet. This thesis applied a mixed method approach, combining results from a cross-sectional online survey (N=474), a lab experiment (N=134) and an agent-based model (ABM) to explore how a change towards sustainable food purchasing may be achieved in society. The methodological approach of this thesis is quantitative confirmatory and exploratory. The online survey, based on main environmental psychology theories (Theory of Planned Behaviour, Norm Activation Model and habit theories) and social network theory, explored which factors significantly influence sustainable food purchasing behaviour. Findings show that social network factors influence sustainable food purchasing behaviour via psychological factors; habit, perceived behavioural control, descriptive and personal norms. Additionally, segmentation of different sustainable behaviour groups (high, medium and low) let to the development of segment specific intervention strategies. The lab experiment, measuring actual sustainable food consumption behaviour, validated and extend these findings by showing that social network members significantly influence sustainable food consumption behaviour compared to strangers. I further applied the empirical findings and theoretical knowledge to build an ABM to understand (1) the spread of sustainable food purchasing behaviour, and, (2) how three social network factors (i.e. network size, percentage of sustainable shoppers and percentage of food discussion partners in the social network) influence this spread of sustainable consumer behaviour via psychological factors shown to be relevant to influence sustainable purchasing behaviour (i.e. intention, habit, personal and descriptive norm). Findings provide evidence that there is (1) a threshold effect during the spread of sustainable food purchasing behaviour in social networks as the spread of sustainable food shopping behaviour is fastest at the beginning phase of the experiments, slowing down towards the middle and end phase. The speed of the spread of behaviour is significantly influenced by the size of the social network and the percentage of initial sustainable shoppers in the personal network (2). This research provides a first glimpse of what behaviour change towards sustainable food shopping may look like with the influence of social networks. Intervention and policy recommendations are discussed.