The Theory of Planned Behaviour doesn't reveal 'attitude-behaviour' gap? Contrasting the effects of moral norms vs. idealism and relativism in predicting pro-environmental behaviours

The inconsistency between pro-environmental attitudes and behaviours called the 'attitude-behaviour' gap, has been reported in many scenarios relating to sustainable actions. However, the reasons for it are not entirely clear. It has been proposed that the 'attitude-behaviour' gap is driven by the moral dimension whereby moral attitudes fail to translate into subsequent moral behaviours. If so, the lacking integration of moral dimension into the environmental domain serves as a generalisable factor to improve the accuracy of predicting pro-environmental behaviours. Hence, we aimed to explore (i) whether the addition of a moral element to the Theory of Planned Behaviour (TPB) shows the 'attitude-behaviour' gap and (ii) whether the ethics position questionnaire (EPQ) is a more suitable measure of morality within the TPB framework, as compared to that of moral norms. The results from 181 US MTurk participants disclosed that the addition of the moral element to the TPB framework did not reveal the presence of the 'attitude-behaviour' gap, despite both moral norms and idealism significantly predicting pro-environmental attitudes. The findings do not indicate whether moral norms or idealism should be used as a more accurate measure of morality within the TPB framework, although relativism was found to have no significant effects. Further investigation of why the moral element does not reveal the 'attitude-behaviour' gap within the TPB framework predicting pro-environmental behaviours would help understand the reasons why rational choice models tend to overestimate theoretical vs. real-life engagement with sustainability.