Because people often say one thing and do another, social psychologists have abandoned the idea of a simple or axiomatic connection between attitude and behavior. Nearly 50 years ago, however, Donald Campbell proposed that the root of the seeming inconsistency between attitude and behavior lies in disregard of behavioral costs. According to Campbell, attitude- behavior gaps are empirical chimeras. Verbal claims and other overt behaviors regarding an attitude object all arise from one "behavioral disposition." In this article, the authors present the constituents of and evidence for a paradigm for attitude research that describes individual behavior as a function of a person's attitude level and the costs of the specific behavior involved. In the authors' version of Campbell's paradigm, they propose a formal and thus axiomatic rather than causal relationship between an attitude and its corresponding performances. The authors draw implications of their proposal for mainstream attitude theory, empirical research, and applications concerning attitudes.

According to Hardin (1968), environmental deterioration stems from self-interest undermining people's resource conservation in the collective interest. Not surprisingly, selfless prosocial motives, such as personal feelings of moral obligation, have often been recognized as a key force behind people's environmentalism. In our research, we anticipated that environmentalists-people with an inclination for pro-environmental engagement-would possess a propensity to generally act prosocially. In an extension of previous work, we expected that a well-established self-report measure of past conservation behavior would predict people's active participation in a psychological experiment. Based on subjects' degree of environmental engagement, originally established in 2003, we re-contacted a sample of 502 persons in 2005. Of these 502 (68.5% low, 31.5% high in environmentalism), 131 showed up for the announced experiment. Among those participants, we found that environmentalists' prosocial personalities were additionally reflected in their social value orientations. Ninety percent of the environmentalists turned out to be prosocials, whereas only 65% of the less environmentally engaged subjects were prosocials. Overall, our findings lend credit to a notion of environmentalism as an indicator of even subtle quantitative differences in a person's prosocial trait level. By and large, environmentalists acted more prosocially even in mundane activities unrelated to environmental conservation. Additional evidence comes from the commons dilemma experiment in which the participants partook. There, we generally found comparatively more cooperation with others for the collective good from people high in environmentalism. Our findings represent circumstantial evidence for a prosocial propensity dimension along which people differ, and which is also reflected in people's pro-environmental behavioral performance. If, however, environmentalism has to be regarded as indicative of a prosocial trait rather than a state-like motive, high hopes for moral norms and other prosocial motives in environmental conservation do not seem warranted.

Despite the very positive-as measured by market surveys-attitude towards eco-innovations and sustainability in general, the actual market penetration of green products and practices generally falls behind the expectations. In this paper we argue that considering difficulty of engagement, as used in the Campbell Paradigm, is of critical importance when modeling diffusion of ecoinnovations. Such a notion of difficulty possesses three desired properties: (i) parsimony-it is represented by a single value, (ii) interpretability-it can be regarded as an estimator of the otherwise complex notion of behavioral cost, and (iii) applicability-it can be easily measured through market surveys. In an extensive simulation and analytical study involving empirically measured difficulty and an agent-based model spanned on different social network structures, we show that innovation adoption may exhibit abrupt changes in market penetration as a result of even small changes in difficulty. The latter may be of particular interest to policy makers who have to make strategic decisions when introducing socially-but not necessarily individually-desired products and practices, like dynamic or green electricity tariffs.

Environmental attitude and ecological behavior were investigated in relation to the use of nature for psychological restoration. Specifically, with survey data from 468 German university students, the role of environmental attitude was investigated as a mediator of the restoration-behavior relationship. Assuming that positive experiences in nature can have a broad influence on environmental attitudes, the New Ecological Paradigm (NEP) scale, an attitudinal measure with broad scope, was adopted. Hierarchical regression analyses indicated partial mediation by environmental concern. The study helps to consolidate the restoration theme in the growing literature on positive motivations for ecological behavior.

Hypocrisy-professing a general attitude without implementing corresponding attitude-relevant behavior-is, according to Ajzen and Fishbein (2005), commonly found in attitude research that aims to explain individual behavior. We conducted two studies that adopted the Campbell paradigm, an alternative to the traditional understanding of attitudes. In a laboratory experiment, we found that specific attitude-relevant cooperation in a social dilemma was a function of people's pre-existing general environmental attitude. In a quasi-experiment, we corroborated the reverse as well; engagement in attitude-relevant dietary practices was indicative of environmental attitude. When using Campbellian attitude measures, there is no room for hypocrisy: People put their general attitudes into specific attitude-relevant practices, and differences in people's general attitudes can be derived from their attitude-relevant behavior.