Christopher studied the pivotal role that autonomy - self-determination - plays in sustaining human behaviour and decision making processes. When it comes to motivating people to make environmentally friendly decisions, Christopher found that, instead of surveillance or incentivisation, autonomous motivation is the key mediating factor between group norms and sustainable behaviour. That is, people are more likely to make sustainable choices if they feel as though their decisions are autonomous.
You can find Christopher’s dissertation, “Group-Influenced Autonomous Motivation for Pro-environmental Behaviour: Factors influencing the internalisation of group norms as autonomously motivating” here.