We are all individuals : Within- and between-subject analysis of relationships between pro-environmental intentions and motivations

Motivations to engage in pro-environmental behaviours (PEBs) are often investigated using psychological theories such as the Theory of Reasoned Action. Though many psychological theories propose causal mechanisms operating at the level of the individual, studies often analyse cross-sectional data on psychological constructs with between-subject analyses. This approach is sensitive to confounding effects arising from differences between individuals, as opposed to capturing within-subject mechanisms. With pooled data from two surveys, we show that analysing relationships between motivations and intentions within subjects, across behaviours, can yield divergent results when compared to analyses between subjects, within specific behaviours, or using aggregate data. Specifically, whereas between-subject analyses suggested that individuals who perceived strong social pressure had only weakly stronger PEB-intentions, a within-subject analysis revealed that individuals were more inclined to perform PEBs for which they perceived social pressure. Likewise, economic gains were only in some cases related to PEB-intentions between-subjects, but individuals were more likely to perform PEBs that produced economic gains. We elaborate on what these diverging findings imply