Comparing and Combining Theories to Explain Proenvironmental Intentions

This article addresses the need for systematic theory comparison and development\udin environmentally significant behavior (ESB) research. Using logistic\udregression (N = 398), models based on Schwartz’s norm-activation\udtheory (NAT) and Ajzen’s theory of planned behavior (TPB) were compared\udas explanations of drivers’ intentions to reduce or maintain their car use for\udcommuting. NAT explained more variance (McFadden R2 = .342). A model\udusing NAT and TPB constructs was also tested. This explained more variance\udthan either individual theory (McFadden R2 = .379). A personal-normative\udvariable (NAT) and perceived behavioral control (TPB) were the only statistically-\udsignificant predictors of intentions in the model derived from both theories.\udIt is argued that combining NAT and TPB constructs accounts for a range\udof influences on car-use intentions that neither individual theory fully captures.\udA combined model may also apply to other ESBs, especially those perceived\udas reducing personal utility (i.e., entailing sacrifice)