We don’t always act consistently when it comes to our environmental behavior. We might only use public transport and our bikes in our daily lives, just to hop on an airplane to go on holiday. In psychology, this phenomenon is called moral licensing, which is one example of behavioral spillover in the environmental domain.
A few weeks ago, I was ready to go on vacation. With my COVID vaccination passport in hand, I hurried to Munich airport in the early hours of a Tuesday morning with a good friend of mine, looking forward to spending some well-deserved time off in Portugal.
I am going to be honest here – I know flying is terrible for the climate, airplanes secretly terrify me, but I also love to travel, so every once in a while, I still do step on an airplane. And just to defend myself, I am generally a person that acts quite environmentally friendly. I don’t own a car, live in a small space, eat a vegetarian diet and buy lots of seasonal and local produce that I like to carry home from the Saturday market in my cotton tote bag (ain’t no plastic touching the organic strawberries I just bought!).

After a first environmentally-friendly action, the question is – does the person continue on this path or not?
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So here I am, trying to tell myself that it’s ok to fly every once in a while, because you know – I am doing lots of good things for the climate and environment at many other times during my everyday life. In reality, I know that the equation is not true, but we all make mistakes.
What I have described above is actually a thought process, which is rather common – you might have even caught yourself thinking this way once. In psychology, this way of thinking has been coined “moral licensing”, referring to the process of justifying immoral actions (e.g. flying) by having previously engaged in moral behavior (e.g. carrying home your organic strawberries in a cotton tote bag – I hope you see the irony). In a way, you can imagine moral licensing as a kind of “moral bank account”. By engaging in some kind of good behavior or moral action, one seemingly deposits credit into a moral account, which can then balance out any subsequent non-moral behavior.
Spillover effects of environmental actions
It is no big new that humans don’t think and act rationally all the time, but is our thinking actually that flawed that after engaging in some kind of pro-environmental action, we use this as an “excuse” to engage in other actions that are harmful to the environment?
Moral licensing is not the only term that has been used to explain how engaging in one kind of pro-environmental behavior can negatively affect subsequent behaviors. Moral licensing, single action bias, rebound effects, gateway effects or the contribution ethic– all of these labels fall into the definition of what in general is called “spillover effects”. Spillover effects are defined as observable and causal effects one behavior has on another. More specifically, to count as a spillover effect, the behaviors must be different (e.g. water conservation and electricity saving), sequential (where on behavior follows another), and sharing a motive (e.g. pro-environmentalism).

Engaging in an environmental behavior can produce both negative and positive spillover effects.
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What I described above (flying after engaging in other pro-environmental behaviors) would constitute a negative spillover effect, meaning that the adoption of one pro-environmental behavior decreases the likelihood for people to engage in another pro-environmental behavior. Luckily, spillover effects can be positive too in the sense that the promotion of one pro-environmental behavior makes it more likely for people to adopt other pro-environmental behaviors, but more on that later. Let’s first dive a bit deeper into what the research has to say on negative spillover effects.
Negative spillover effects
As I just mentioned, my choice of transportation mode to go on vacation could be considered a negative spillover effect, in this case moral licensing. Of course, I did not do research on my own choice of transport mode and can’t say with absolute certainty that me taking the bike and public transport at home actually caused me to take a flight to go on vacation. However, there is some correlational research that indicates that people who act in environmentally-friendly ways at home are actually the most likely to use carbon-intensive modes of transportation when on vacation. Furthermore, a focus groups study has found that participants who acted pro-environmentally at home did not feel a need to do the same on vacation. Such moral licensing effects have also been found with regard to other transportation modes, with the purchase of a fuel-efficient vehicle being linked to driving less environmentally responsible.

On vacation, people do not always act as environmentally-friendly than at home.
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Indications for moral licensing are also present in the energy consumption domain. One study found that while smart meter feedback information did lead to participants decreasing their energy consumption, they were also less likely to invest in energy efficiency measures compared to a control group. Negative spillover can also occur when on behavior is perceived to compensate for another. For instance, one study reported that people were less likely to contemplate reducing packaging waste when shopping if they believed that recycling addressed the problem. This phenomenon is sometimes referred to as the contribution ethic, namely believing that if one has fulfilled their obligations and made an appropriate contribution to a moral goal (such as protecting the environment) one may feel justified to “rest on one’s laurels”. Such perceptions may also partly be linked to the notion of “why should I act when others are not?”.
Some research has even attempted to prove the existence of cross-domain spillover effects, linking environmentally-conscious shopping choice to subsequent dishonesty. However, a second team of researchers was unable to replicate this study on moral licensing at a later point in time, providing no evidence for a cross-domain spillover effect. These were just a few examples of negative spillover, but let’s focus on the positive effects next, as everything else will exceed the limits of this post.
Positive spillover effects
Just as some behaviors can negatively spill over to others, positive spillovers can occur. According to research, behaviors cluster into distinct conceptual categories, such as “waste and recycling”, “transportation” or “green consumption, meaning that if an individual engages in one behavior from a certain cluster, they are likely to also do others (this does of course not ALWAYS happen). Evidence for the link between behavioral similarities and positive spillover also comes from a study that was conducted in Denmark over the course of 20 months. Analyzing data from retail scanners and shopping loyalty cards, the researchers found a consistent spillover effect from purchasing organic dairy products to a range of other organic food products. From personal experience, I can especially relate to this study (and maybe you can too!) – at first, I only bought certain types of produce that were considered to be heavily loaded with harmful pesticides from the organic section, but slowly started to add more foods, with to date, the majority of the food I am buying being organic.

Positive spillover effects have been shown to occur with regard to food shopping.
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Positive spillover can also occur for similar behaviors across settings, such as from a work setting to a home setting. For example, a study has shown that energy conservation behaviors transferred from work to home, just as recycling behavior did. Having read the above part on negative spillover effects with regard to transportation mode and vacations, you might wonder why people do not always behave consistently across setting. This could be because behavioral consistency across settings might be constrained by difference in perceived sense of responsibility and autonomy in different contexts.
Positive spillover effects can occur with dissimilar behaviors too. A longitudinal study over a 6-week period reported that following an intervention that promoted the purchase of organic foods and eco-labeled products, positive spillover effects occurred on behaviors such as recycling, travel mode choice, energy/water conservation and volunteering for a green cause. It should be noted though, that these effects were only found for people who performed these behaviors infrequently prior to the intervention.
When does spillover occur?
Many people are constantly busy with negotiating inconsistencies between their environmental awareness and concern as well as consumerism and non-sustainable lifestyles. So what is it that causes positive behavioral spillover at certain times? Despite growing policy and research attention, the processes driving spillover effects remain unclear. Several theories and concepts can offer explanations. Some studies link spillover to identity processes, asserting that acting sustainably may become integrated with our self-concept and that we infer how to act by reflecting on our past behavior and who we are as a person. In other words, by engaging in certain pro-environmental actions, one might see oneself as “green”, which thereby can make it more likely to engage in other green behaviors too. Other studies refer to cognitive dissonance theory as an explanation, which posits that people are motivated to think and act consistently (i.e. pro-environmentally) to avoid feeling discomfort. However, consistency might not concern those for whom the environment is not as important. Last, social norms can contribute to behavioral spillover, by giving off the perception that engaging in certain behaviors is approved and done by others as well as by possibly inoculating against perceived inequity (“Why should I do this if others don’t?”).
It's the net spillover effects that matter
Returning to the question posed in the title of this blog post – does engaging in environmentally-friendly behaviors license us to sin? Well, absolutely not, but unfortunately we do sometimes fall prey to our own cognitive biases, thinking that we have done our part for the climate and environment already, so it’s fine if we slack a bit here and there as well. On a brighter note, positive spillover effects can occur too, and it is simply necessary to take the halo associated with green behaviors with some reservations.
It is in the best interest of policymakers to understand spillover effects in an effort to design effective energy and environmental policies and respective communication strategies, which may require behavior change to achieve meaningful effects. It is especially important to understand the net effect of an intervention after accounting for both negative and positive spillover effects. A certain policy or intervention might have both positive and negative spillover effects. However, simply concluding that said policy or intervention is ineffective due to the presence of negative spillover effects is problematic, since the net effect of both positive and negative spillover effects might still be positive overall.