The Basic Idea

Consider the process you go through when you subscribe to a service. It might be subscribing to a weekly food box service, to a gym, or to Masterclass video lessons. The process is easy:  enter your information and a payment method, and voila! You are subscribed and the first product or session might even be free. Now, contrast this with the difficult process you have to go through if you want to cancel a subscription. Often, cancelling a subscription requires at the very least a phone call, during which you have to explain why you want to cancel, while the operator tries to convince you against it. The difficulty is no mistake; it is an intentional design technique known as sludge.

Sludge is essentially the opposite of a nudge. While nudges try to push people to make better decisions by making certain choices easier than others, sludges make a process more difficult with the goal of creating friction, which makes the consumer less likely to continue the process. Sludge, however, is not always put in place to get more money out of people, or to disadvantage the consumer in some way – sometimes, they can be used to encourage people to be thoughtful about their behavior. For example, privacy protection requirements can seem annoying, but this friction causes us to think twice about what data we are sharing online and can encourage us to be more careful with it.1

Sludge can take two forms. It can discourage behavior that is in a person’s best interest such as claiming a rebate or tax credit, and it can encourage self-defeating behavior such as investing in a deal that is too good to be true. Let’s continue to encourage everyone to nudge for good, but let’s also urge those in both the public and private sectors to engage in sludge cleanup campaigns. Less sludge will make the world a better place.

– Richard Thaler, in his article“Nudge, not sludge.”2

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Key Terms

Nudge: a behavioral science technique that aims to influence people to make optimal decisions.

Choice Architecture: the design of how options are presented to us.

Framing Effectthe idea that information can be valued differently depending on how it is presented.

Friction: an obstacle that is put in place in order to make a decision more difficult. Friction is an impediment and is used to dissuade people from making a certain choice.


Although the terms ‘nudge’ and ‘sludge’ have a more recent history, the idea of an environment impeding and facilitating certain behaviors was theorized as early as 1890. In 1890, American psychologist William James published a book, The Principles of Psychology, which suggested that people’s ability to get things done was impacted by the environments in which they were making decisions.1

Two important behavioral scientists, Richard Thaler and Cass Sunstein, took James’ ideas a step further by suggesting that since people’s environments impact the decisions they make. Governments and other authorities can use small influences within people’s environments to push individuals towards certain behaviors. While not wanting to limit people’s freedom by suggesting people should be forced to make particular choices, Thaler and Sunstein believe that nudges can help people make more rational choices themselves, which they write about in their book Nudge: Improving Decisions About Health, Wealth, and Happiness:

“A nudge, as we will use the term, is any aspect of the choice architecture that alters people’s behavior in a predictable way without forbidding any options or significantly changing their economic incentive.” 3

The framing effect shows us that the way options are presented to us matters. By understanding the cognitive biases that influence people’s thinking, Thaler and Sunstein hope that nudges can  be used to reduce the fallacies that people fall victim to when making decisions. These should  be well-intentioned; however, if choice architects can figure out what cognitive biases cause people to favour particular choices over others, they can also use the information to their own advantage rather than to help the consumers make the best choices for themselves. For example, companies may nudge customers toward more expensive products, therefore using available information about consumer decision-making to advance their own profit.

While Thaler and Sunstein originally thought nudges were a behavioral science tool that could help individuals, they soon realized that nudges also had the potential to be used to take advantage of people’s bounded rationality. 10 years after publishing their book Nudge, Thaler published an article entitled “Nudge, not sludge” which described activities that were “essentially nudging for evil” (431); in other words, sludges.2 There is a distinction here between sludges as simply evil nudges, and sludges as a process, good or bad, that makes it more effortful to make a certain decision. The term is usually used in the latter sense but you’ll see both crop up throughout the literature.

Sunstein continued to examine sludges throughout his career, and has a book, Sludge, coming out this year. The book takes a look at all the administrative red tape people have to go through to get their most basic needs. As a result, Sunstein suggests that sludges actually prevent people from exercising their constitutional rights.


Oftentimes, sludges leverage friction to disable someone from making the decision that is best for them. The difficulty of cancelling subscriptions or memberships is likely an experience we’ve all had, but it may not be as serious as other forms of sludges, such as the difficulty of applying for welfare.

There are three different departments that someone who is applying for welfare in the U.S. has to engage with: the first for taking applications, the second for processing applications, and the third for providing welfare payments.1  There are similar obstacles and frictions for accessing healthcare in various countries.  People who need financial support or health services encounter sludge and might give up before they get the help they need. According to Sendhil Mullainathan, these obstacles contribute to the bandwidth tax, and help keep poor people poor.

Politics are another area in which sludges can manipulate outcomes. Nudges can be used to increase voter participation, such as by taking advantage of the status-quo bias and automatically registering people who apply for a driver’s license. However, sludges can be used to prevent easy access to voting as well, which might include purging people who have not voted recently from the eligible voters list, or making polling stations very far from particular neighborhoods.2

Understanding that sludges can be used just as easily as nudges can has serious implications for the ethical understanding of choice architecture. One criticism of nudges has always been that pushing people to make certain decisions limits their freedom. These criticisms are typically more concerned with the underlying ideologies of nudging, rather than the outcomes. That being said, when outcomes are intentionally designed to maximize profit rather than rationality, we have to wonder whether manipulating choice environments is ever ethically sound.4

It is almost as if choice architecture is a superpower and architects have to decide whether to use their powers for good (in a ‘nudge’ form) or for evil (in a ‘sludge’ form). The issue is that it is often impossible to create choice environments that are neutral and grant people the freedom to make whatever choices they want.


Nudges have come under scrutiny for their ability to actually effect change. In one study, Cass Sunstein found that when people were told that they were being influenced by choice architecture, even when told it was in their best interest, they would react negatively and act against the nudge.5 This research suggests that the same might be true for sludges – if consumers are informed about the sludges companies use to influence them, they might be able to resist the impact and exercise more freedom. This might be especially true in situations in which  sludges cause people to lose money, because of loss aversion, a cognitive bias suggesting that we tend to avoid loss more than we attempt to achieve gain. Because of loss aversion, we are likely to be motivated to cancel our subscription, no matter the difficulty, for fear of losing money.

Sludges are typically discussed with a motive in mind of advancing particular agendas, rather than ensuring the good of the people. That being said, perhaps there is room for sludges to  operate more similarly to nudges. As Thaler and Sunstein have claimed, it is impossible to avoid choice architecture altogether; options have to be presented in a particular way and whatever presentation choice is made will influence decision-making processes.5 There may be no ‘neutral’ choice environment. Instead of getting rid of nudges and sludges, it might be more important to ensure that people designing them have the right intentions and can understand when to use one versus another to  benefit people.

Personality Types and Sludges

Sludges work most effectively by preying on cognitive biases that turn people away from making the best decisions. When we try to perform an action and face friction – like jumping through hoops to cancel a subscription – these biases, like laziness or procrastination, can frequently appear. However, people tend to procrastinate to varying degrees, which might mean that different kinds of people are impacted by sludges differently.

University of Toronto professors Dilip Soman and Kim Ly conducted research into a broad range of studies to observe  how people respond to choice architecture. They theorized that people could be split into three categories based on their responses: motivated enthusiasts, die-hard opponents, and naive intenders.6 They hypothesized how these three groups of people would respond to behavior change, as defined as “a change in decision or a change in a series of requirements and actions needed to accomplish a particular outcome.6

Motivated enthusiasts are highly motivated people who are likely to agree to enacting particular kinds of behaviors and are unlikely to be influenced by tendencies like procrastination. Die-hard opponents are those who are opposed to the behavior change being asked of them, which means if they are aware of nudges or slides, they are not likely to be impacted by them. Naive intenders are people who believe in what is being asked of them and plan to do it, but they never follow through. Naive intenders are the most likely to be impacted by sludging because they are likely to delay any behavior that has to overcome friction, believing they will get around to it later but never actually following through.6

As Soman and Ly’s investigation suggests, more research into sludges is needed in order to fully understand how sludges impact different types of people. Since sludges do not impact everyone in the same way, companies or public services might not know where sludges are present in their design and how they are impeding behavior. Having greater knowledge about  how different people respond to sludges could help mitigate their negative effects, which is why Soman has helped develop a tool that can help organizations find areas where sludges are impacting end-user behavior.6

Welfare and Sludges

There are many government programs intended to ease the burdens faced by low-income populations. Although these programs are embedded within complex and messy politics, oftentimes, they are put in place to help people. However, since there exists a vast distance between policy- and program-makers and the intended recipients, government employees might not always take into account how to make access to the programs as easy and smooth as possible.

One example of a well-intended program that fell victim to a sludge was the Canada Learning Bond. The bond intended to encourage low-income Canadians to send their children to post-secondary education, as they would receive money that could help cover future expenses. In order to receive the bond, parents had to apply for a Social Insurance Number (SIN) as soon as their child was born, so that they could receive the $2000 payment in their SIN account.1

However, when the policy was first launched, the government found that less than 50% of eligible people were taking advantage of it. It later became known that the reason for the poor take-up rate was that parents had to apply for a SIN within three months of their child’s birth.1 The life of a new parent is incredibly stressful and applying for a SIN is not likely a top priority . Since these accounts had to be applied for in person, parents could not find the time to do so  and forewent the bond as a result. Once again, this is a prime example of the bandwidth tax in action.

After this information came to light, the government tried to make applying for a SIN easier by putting the forms online and automatically sending them out to families upon their children’s birth. While this effort helps  diminish the sludges that impede  these new parents from the initiativ , the required forms are still a burden. We might instead ask why any forms have to be filled out at all.1 Can sludges be removed altogether, with children automatically receiving a SIN when they are born?

Related TDL Content

Do I Agree? Cognitive Bias and Terms of Service

In this article, our writer Tiago Rodrigo discusses the familiar tendency to quickly scroll through Terms of Service and click ‘Agree’ without reading the fine print. This occurs because people tend to avoid an overload of information. Companies know about and purposefully leverage our avoidance of information – through a sludge – to make consumers agree to things they  probably wouldn’t otherwise (such as waiving the right to data privacy).

Jesse Itzkowitz: Nudging Against Polarization

In this episode of The Decision Corner podcast, we sit down with Jesse Itzkowitz, a behavioral scientist at a leading global market research and consulting firm. Itzkowitz discusses the differences between nudges and sludges and dispels the idea that nudges are all about tricking people. He suggests that companies who use sludges are the ones that we should worry about, although he thinks people will soon see through their manipulations.


  1. Nudge and Sludge: A Conversation with Dilip Soman. (2019, November 12). Civil Service College Signapore.
  2. Thaler, R. H. (2018). Nudge, not sludge. Science361(6401), 431-431.
  3. Thaler, R. H., & Sunstein, C. R. (2009). Nudge: Improving decisions about health, wealth, and happiness. Penguin.
  4. O’Brien, H. (2019, May 22). Cass Sunstein and the rise and fall of nudge theory. NewStatesman.
  5. Kane, P. (2019, November 16). Playing politics: exposing the flaws of nudge thinking. New Scientist.
  6. Soman, D., Cowen, D., Kannan, N., & Feng, B. (2019). Seeing sludge: Towards a dashboard to help organizations recognize impedance to end-user decisions and action. SSRN Electronic Journal

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