Behavioral spillover theory has potential for promoting meaningful behaviour change. Spillover occurs when engagement in environmental behaviors affects the adoption of other environmental behaviors. By testing a new experimental
model of spillover, this article is the first to concurrently investigate three predicted mechanisms of spillover—self-identity, self-efficacy, and contribution ethic—on different types of environmental behavior. The experimental spillover model examined how triggering self-perceptions (i.e., self-identity, self-efficacy, and contribution ethic) may influence the likelihood of spillover to occur from engagement in household behaviors to intentions for other environmental behaviors. Triggering self-identity was associated with increased private- and public-sphere intentions. Contrary to expectations, contribution ethic was not associated with decreased intentions, and instead was associated with increased public-sphere intentions. Self-efficacy did not uniquely influence intentions. These findings demonstrate that everyday behaviors can provide an “entry point” for other behaviors, strengthening self-perceptions and generating positive spillover.