Expressing a universal environmental imperative that encourages every individual to consider the environmental effects of their actions is a recent phenomenon. It stems from the 1972 Meadows report , which underlines the finite nature of the planetary resources used for economic activity. The best known formulation is probably that of philosopher Hans Jonas from 1979 : “Act so that the effects of your action are compatible with the permanence of genuine human life”. In 1980, philosopher Michel Serres proposed a “Natural Contract” , which asserted the interdependency of humanity and the planet, and suggested that all actions must be evaluated in the light of their impact not only on man, but also on the ecosystem. It was no longer, therefore, simply a question of combating the environmental damage caused by certain human activities deemed to be harmful, but of taking into account, at individual and collective level, the effects of each of our actions on the ecosystem.
This philosophical formulation, which coincided with an incipient political environmentalism and action taken by various activist groups against the backdrop of the first energy crisis, would progressively lead state governments and local authorities to take action. From the 1990s onwards, the French government tasked intermediaries such as the French Environment and Energy Management Agency (Ademe) with rallying citizens to the cause and imposing new obligations of good citizenship on consumers, notably through the promotion of “small gestures”. We can observe similar policies in many European countries. In the United Kingdom in the 2000s, for example, the Ministry for the Environment established a very precise list of virtuous behaviours and ways of promoting them. What are the effects of these public incentive systems? Do individuals follow these environmental recommendations? Why?
In recent years, many social science research projects in various disciplines have suggested answers to these questions. Here, we present the most important of these projects in turn: first of all, the economic research focusing on understanding individual behaviour, and then the sociology research looking at social practices on a wider scale.
PSYCHOLOGY AND EXPERIMENTAL ECONOMICS: BEHAVIOURAL APPROACHES
A first set of research projects starts from the hypothesis that individuals’ behaviour is the fruit of freely taken decisions. This scenario of an individual free to determine his/her own actions is generally paired with the assumption that said individual is completely rational. To simplify to the greatest possible extent, his/her behaviour is thus that of the perfectly logical agent known as homo oeconomicus. This agent: (i) has all the information necessary to take his/her decisions; (ii) learns (i.e. when he/she makes a mistake, he/she will try not to make it again); and (iii) is constantly trying to optimise the benefits of his/her actions. This kind of simple behavioural model leads to an approach based on (a) incentives or disincentives, often of a financial nature; (b) information campaigns; and (c) strict regulations. One illustration are air pollution reduction policies, which simultaneously make use of all three levers: supplying information (Bison futé, Sytadin.fr), changing the relative cost/benefit ratios of cars and public transport (congestion charges and taxes on the one hand, subsidies on the other) and, as a last resort, establishing rules (pedestrianisation, alternate-day travel).
The most recent evolution of this model resides in its consideration of the limits of rationality and information, following on from the pioneering work of H. Simon  and the analysis of Kahneman and Tversky  (Nobel economics laureates in 2002). Their research demonstrated that decisions were taken in a particular cognitive framework, subject to multiple representational and interpretative biases. In other words, in daily life, people generally fall back on habits, either doing things “like everyone else” or resorting to quick simplifications (heuristics). For these researchers, heuristics can be a problem: for example, cognitive myopia causes people to systematically overestimate gains that are more immediate in time or space, making it difficult to establish routines that are beneficial in the medium and long term (e.g. not investing in thermal insulation due to the immediate cost, without seeing the long-term benefit). We could also mention an aversion to losses and a tendency to make default choices.
These biases (such as lack of foresight, suboptimal choices and weak willpower), could be not only seen as the causes of inefficient economic behaviour, but also as potential drivers to make behaviour more effective. Examples of this approach can be found in the “nudges” suggested by economist Richard Thaler and lawyer Cass Sunstein. Without mentioning all of them, we can describe some of the principles used to make a decision-making framework that favours the preferred option:
- Relevant information: In a purchasing decision, only simple information that requires no projection into the future is taken into account. Ecolabels that use colour coding to display the energy consumption of household appliances provide just such information and have proved effective.
- Reference to a simple form of social identity: For example, a study on carsharing (Josset 2015) showed that people who were approached as belonging to a social group (“INRIA researchers, “Supelec students”, etc.) tended to increase their participation in a project to help one another get around (carsharing, information sharing, etc.)
- Many examples show the power of the “default” option. For instance, German electricity suppliers offer their subscribers a choice between energy from “conventional” sources or more expensive green energy. While less than 1% of households opt for the latter when given a free choice, 99% do so when green energy is presented as the default option.
Nudges have received a number of criticisms, however. In terms of their effectiveness in changing behaviour, the results of certain American nudges could not be reproduced in Europe, with social and cultural norms probably coming into play in individuals’ calculations. From an ethical point of view, we can not only dispute whether it is legitimate for a democracy to manipulate individuals’ decision-making framework, but also point to the pitfalls encountered in the practical application of such strategies: we know, for instance, that one way of increasing sorting of waste is to have people believe that all their neighbours are doing it… So do we have to keep watch over everyone? Or do we just lie, knowing that announcing a high rate of recycling will be more effective?
The third and final criticism encompasses two aspects. First, the implementation cost is often much higher than that of a traditional awareness campaign and the results are sometimes disappointing (a UK parliament report  concluded that nudges only work for simple practices and if the people concerned are already unambiguously convinced of the benefits of changing their behaviour). Secondly, there is resistance from some players (manufacturers, etc.) who may be negatively impacted by the targeted changes in behaviour.
PRACTICE THEORY (SOCIOLOGY)
However, there are other elements that can explain the inertia of practices and the frequent failure of policies based on providing individuals with financial incentives or improved information, such as “practice theory”, an approach developed from the mid-2000s by Elizabeth Shove and Alan Warde. It is characterised first and foremost by a change of scale, focusing on practices shared by social groups, rather than on individual behaviour. Secondly, it marks a departure from the rational decision-making model: rather than the choices of individuals, practice theory describes routines. As Warde puts it, “the overall thesis is that much behaviour is outside, or only at the verge of, the boundaries of deliberate, rational or prospective thought” .
The thinkers behind this theory identify three crucial dimensions. The first is cognitive, covering the discourse and representations surrounding the activity in question (cooking, recycling, mobility, etc.); the rules, explicit or otherwise, that govern it; and the meaning individuals attribute to it. The second covers all the aspects internalised by individuals: habits, routines, ways of doing things, and the feelings a practice generates. The third dimension concerns the infrastructure, material arrangements and technical and economic systems that structure practices. For example, to report on drinking water consumption in connection with hygiene, we must look both at social representations (“you have to shower every day”, a norm constructed from the 1950s), internalised bodily routines (the feelings associated with showering, body odours, etc.), and the fact that water consumption is invisible because the water meter is hidden in most homes, due to a deliberate historical choice by operators.
In this analysis framework, policies providing information or financial incentives to the consumer, have no impact on established routines, cannot remove the time constraints affecting everyday activities, and do not take account of the constrictive force of infrastructure.
Strengers , for instance, examines the effect of installing meters that make water and electricity consumption visible within the home (IHD, in house display), based on a survey of 28 Australian households. She begins with a reminder that most studies observe a limited effect – a drop of 0 to 15%, often restricted to the beginning of the experiment.
First of all, she notes that such meters do correct the infrastructure by making individual consumption more visible, but observation of the meter remains essentially disconnected from the act of consumption. Such initiatives appear relatively ineffective in transforming routines and in understanding the practices they are intended to govern. The discourse focuses solely on optimisation and waste. At no point are lifestyles (and the hygiene and comfort rules on which they are built) questioned; hence the highly marginal and temporary effectiveness of these systems, as demonstrated by this quote from an interviewee: “It is good to know which devices trigger the red light, but they are all things we need to use anyway… so what are we supposed to do?”
Approaches designed to change behaviour are only truly effective when they combine all three dimensions, working simultaneously on representations, specific habits and infrastructure. Other research shows that this is even more true when such actions are supported by legislation. One of the most commonly cited examples of an effective policy is the Cool Biz Initiative in Japan, which drastically reduced energy consumption linked to office air conditioning systems through a combination of regulatory requirements, discourse on norms (on what to wear in the office) and the creation of new clothing lines.
Both economic and sociological research underlines the importance of habits and representations in understanding ordinary consumption behaviour and ways of transforming it. Both disciplines emphasise the limits of policies based on providing information or financial incentives to consumers, which are more often than not incapable of transforming habits that have been anchored in consumers’ bodies, infrastructure and social rhythms. They differ, however, in the solutions they recommend: behavioural economics suggests favouring green nudges, pushing individuals towards the right choices without explicitly getting them to commit to a cause. Sociologists, meanwhile, advocate more ambitious policies that act on individuals’ representations as well as their action frameworks.
 Club de Rome, « The limits to growth » (1972)
 Hans Jonas, « The Imperative of Responsibility » (1979)
 Michel Serres, « The Natural Contract » (1980)
 Herbert Simon, « Models of bounded rationality » (1982)
 Kahneman et Tversky, « The framing of decisions and the psychology of choice » (1981)
 House of Lords – STSC Committee – « Behaviour Change Report » (2011)
 Alan Warde, The Practice of Eating (2016)
 Yolande Strengers – « Negociating Everyday Life: The Role of Energy and Water Consumption Feedback » (2011)