Autonomous communication with normative information facilitates positive spillover: promoting pro-environmental behaviors in a local setting.

A pro-environmental behavior (PEB) intervention may increase the adoption of other PEBs that were not targeted by the intervention, leading to a positive spillover effect. Communication that both support autonomy, as defined by self-determination theory, and compliance with descriptive norms may promote the targeted PEBs and positive spillover effect. Such communication may enhance autonomous motivation to adopt PEBs. A pilot study (N = 350) about waste management in a university campus found that autonomous communication supplemented by normative information influenced both targeted and non-targeted behavioral intentions, compared to autonomous-only and controlling communication. Findings were replicated in a main study (N = 629). An intervention combining autonomy support and descriptive norms increased the likelihood of a positive spillover effect in contrast to an intervention combining controlling communication and descriptive norms. In both studies, autonomous motivation mediated the positive spillover effect. Results suggest that communication that promotes autonomous motivation by fulfilling basic self-determination needs may have a broader effect on a wider range of PEBs.