Littering is an issue that seems to persist despite the masses knowing it’s a problem. Despite countless campaigns, hefty fines, and the occasional guilt trip from concerned citizens, people continue to treat the world as their personal trash can. But why? The answer, as it turns out, has to do with game theory, particularly in concepts like the Prisoner's Dilemma, public goods, and the free rider problem.
Starting with a classic Prisoner’s Dilemma scenario: you and a stranger are both faced with a choice—dispose of your trash properly or simply toss it on the ground. If both of you choose to dispose of it properly, the park remains clean, and everyone benefits. But if one of you chooses to litter while the other plays by the rules, the litterbug enjoys the convenience while the other person either cleans up or suffers the mess. The worst-case outcome? Both of you litter and the park turns into a mess. The strange thing is, from an individual standpoint, littering often seems like the smarter choice—it’s quick, easy, and there’s no immediate consequence. But when everyone makes that same rational choice, we all lose out. The environment suffers, and so do we.
This behavior isn’t just theoretical. A 2019 study found that about 75% of people admit to littering in the past five years, despite overwhelming public awareness of the issue. It’s a clear case of the Prisoner’s Dilemma playing out in real life. The benefits of littering—convenience, time saved—are immediate and personal. The costs, on the other hand, are diffused across society and spread out over time, making them easy to ignore. So, despite knowing the collective benefit of keeping public spaces clean, individual incentives often drive people to litter.
The problem gets worse when we consider the nature of public goods. A clean environment is a public good—it’s non-excludable (you can’t stop others from enjoying it) and non-rivalrous (one person’s enjoyment doesn’t reduce another’s). However, these characteristics lead to the free rider problem. Why should I go out of my way to find a trash can when someone else will eventually pick up after me? Or if the city will eventually clean up anyway? This mindset is pervasive and leads to a collective action problem where the incentive to cooperate decreases as more people decide to freeload on the efforts of others.
This problem is exacerbated in areas with high population density. The more people there are, the easier it becomes to rationalize that your little bit of litter won’t make a difference. But of course, when everyone thinks that way, it leads to big problems. Take urban areas, for instance—cities spend millions of dollars annually on litter cleanup. In the U.S., it’s estimated that $11.5 billion is spent each year on litter management. Despite these efforts, the problem persists, particularly in densely populated areas where the temptation to litter is higher, and the sense of personal responsibility is lower.
Studies have shown that when people see litter in an area, they are more likely to add to it, a phenomenon coined as “litter begets litter.” This is essentially a breakdown in collective cooperation, something game theory helps us understand. Once littering starts, the perceived norm shifts and others are more likely to follow.
What makes this even more frustrating is realizing that littering is a Nash Equilibrium in the game of environmental conservation. A Nash Equilibrium occurs when no player can improve their situation by changing their strategy while others keep theirs unchanged. Unfortunately, when it comes to littering, the equilibrium often leads to a dirty environment—because once littering starts, each person’s best response is to continue littering. Why should you go out of your way to find a trash can if everyone else is just tossing their garbage on the ground? The result is a stable, yet undesirable, outcome where littering becomes the norm.
To break out of this equilibrium, we need to change the payoffs in the game of environmental conservation. One approach is to increase the incentives for proper disposal. This could mean even higher fines for littering or better public amenities, like more trash bins in public spaces, making it easier for people to do the right thing. Public awareness campaigns that emphasize the long-term benefits of a clean environment and the social costs of littering can also help shift the norms. Some cities have even experimented with positive reinforcement, such as offering rewards for people caught picking up litter rather than just penalizing those who litter. All of these have been done quite extensively, though, and the behavior still persists in many large cities globally. The more modern approach comes from the field of behavioral economics, which I covered in a previous article, where simple nudges can make a difference. For example, placing footprints on the ground leading to trash cans or making bins more visible and accessible has been shown to reduce littering. These small tweaks can hopefully help shift the balance in the environmental game, encouraging cooperation over defection.
Taking Singapore, where I live, as an example, littering is nearly non-existent, thanks to a combination of strict enforcement, cultural norms, and public education. The government’s approach to maintaining a clean environment is well-known, with hefty fines and even public shaming through corrective work orders (where offenders are made to clean public areas while wearing bright vests). This strict approach has instilled a strong societal expectation that public spaces should be kept clean. Over time, these policies have contributed to a cultural shift where cleanliness is a shared responsibility and part of national identity.
On the other hand, Japan offers a parallel, despite its historical scarcity of public trash cans and less overt enforcement compared to Singapore. Japanese society emphasizes respect for public spaces, which is reflected in behaviors like spectators cleaning up after themselves at sports events. This behavior isn’t just about avoiding punishment—it's ingrained in the cultural fabric. The practice of taking your trash home and the collective effort to maintain cleanliness is an expectation passed down through generations, reinforced by education and social norms.
The key takeaway from both Singapore and Japan is that cultural norms and societal expectations can be as powerful as formal policies in promoting positive behavior. The behavioral aspect of littering, then, is deeply bound by these societal norms. Maybe policies should be targeted towards younger generations so that, while changes may not be visible immediately, the act of caring for the environment is passed down as a cultural norm in the future.
Thought experiment:
Consider that the game theory payoffs discussed here aren’t limited to littering. While littering is a basic and somewhat reductionist example, the same principles apply to broader climate issues. For instance, taking public transport instead of driving, conserving water, or reducing energy consumption all follow similar patterns. When individuals act in their own short-term interests, the collective impact is negative. But when society shifts the matrix of rewards and penalties—whether through cultural norms, incentives, or policies—individual behavior can change in ways that benefit the greater good.
So, what other behaviors do we have mental shortcuts for that, when multiplied across society, end up worsening our collective well-being? How can we make the shift to change these behavioral matrices to prioritize societal benefits over individual convenience?
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