1장
When Willpower Isn't Enough: The Science of Self-Binding
Ever had that moment when you desperately want to change something about yourself, but despite your best intentions, you keep falling back into old patterns? You're not alone. In "Carrots and Sticks," Yale law professor Ian Ayres reveals how the right incentives can bridge the gap between our good intentions and our actual behavior. The book has become a quiet phenomenon among behavior change experts, with everyone from Fortune 500 executives to Olympic athletes adopting its strategies. Even Oprah Winfrey featured the book's commitment contract approach during her final season, calling it "the missing piece" in her decades-long weight management journey. Beyond individual success stories, the book's core ideas have transformed corporate wellness programs, addiction treatment approaches, and even how some governments design public policy. At its heart lies a profound insight: sometimes the key to changing behavior isn't more willpower-it's changing the rules of the game itself.
2장
The Power of Commitment Contracts
Alex Moore, an MIT graduate, had a peculiar habit of artificially inducing sneezes by tickling his nose-finding the sensation invigorating but socially awkward. After numerous failed attempts to quit, he tried something different: he put $400 at risk that would go to an organization he despised if he sneezed artificially even once over eight weeks. This wasn't just any bet-it was a commitment contract through stickK.com, a website designed to help people achieve their goals through structured commitments.
The approach worked. After eight weeks, Alex had broken his decade-long habit without losing any money. But when he tried the same approach to fix his chronic tardiness, the results were disappointing. Despite putting $50 at risk with his girlfriend as referee, he succeeded for only a week before getting stuck in traffic through no fault of his own. Rather than accept the penalty, Alex let the commitment slide, then began lying about his arrival times, and eventually abandoned the contract entirely.
This pattern reveals something crucial about commitment devices-they aren't one-size-fits-all solutions. Their effectiveness depends on careful design, proper enforcement, and matching the right tool to the right challenge. While Alex's sneezing contract succeeded brilliantly, his punctuality contract failed because it lacked flexibility for legitimate obstacles and relied on a referee (his girlfriend) who might be reluctant to enforce penalties.
Commitment contracts help solve what economists call "time inconsistency"-our tendency to make plans our future selves won't follow through on. We promise to start dieting "tomorrow," but when tomorrow arrives, we postpone again. These contracts give our present, planning self power over our future, impulsive self by changing the consequences of our actions.
The key insight is that commitment contracts work differently from ordinary incentives. While incentives merely guide choices by making some options more attractive than others, commitment contracts effectively remove certain options entirely-making them "too bad to accept" or "too good to refuse."
3장
The Behavioral Economics Revolution
The behavioral revolution in economics began with a simple question posed by Richard Thaler in 1981: Would you prefer one apple in one year or two apples in one year plus one day? Most people choose the latter. But when asked to choose between one apple today or two apples tomorrow, many become impatient and choose the immediate reward.
This inconsistency fascinated Thaler because it contradicted traditional economic models assuming people make rational, consistent choices across time. Instead, we exhibit what economists call "hyperbolic discounting"-we're relatively patient when choosing between future options but become impulsive when immediate gratification is available.
A vivid demonstration comes from experiments with pigeons. When given a choice between immediate food (2 seconds worth) or waiting 4 seconds for double the reward, pigeons almost never chose patience. However, when the same choice was presented with longer delays (8 versus 12 seconds), the same pigeons became remarkably patient. This mirrors human behavior perfectly.
We see this pattern everywhere. When offered $50 today versus $100 in six months, people often choose immediate gratification. But when the same choice is shifted to one year versus eighteen months, patience prevails. Pregnant women demonstrate this dramatically-preferring natural childbirth when asked a month before labor, shifting toward anesthesia during active labor, then reverting to their original preference afterward.
Walter Mischel's famous marshmallow experiments with four-year-olds revealed that children who could delay gratification for doubled rewards scored approximately 300 points higher on SATs years later. This variation in impulse control predicts significant life outcomes.
Unlike pigeons, humans can organize their lives to overcome temptation through commitment devices-like Odysseus binding himself to the mast to resist the Sirens-allowing our patient "inner Spock" to triumph over our impulsive "inner Homer." Interestingly, follow-up experiments showed that about 30% of pigeons could learn to use commitment devices too, suggesting these strategies aren't uniquely human.
The problem gets more complex with what economists call "sophistication." Berkeley economist Matt Rabin explains that knowing your future self will give in to temptation can sometimes make you surrender immediately. If you know you'll eventually eat cake as an afternoon snack, you might devour two pieces at breakfast. This explains why sometimes self-knowledge becomes a liability rather than an asset.
4장
The Science of Incentive Design
In spring 1996, a law student named Elizabeth approached me with a serious problem-she needed to complete her graduation paper with only weeks remaining. When she submitted only a skeletal draft days before grades were due, I faced a dilemma: fail her or find an alternative. I offered a "provisional low pass" grade allowing graduation, contingent on her agreement to donate $100 monthly to charity if she missed the September deadline.
Years later, I discovered Elizabeth had been faithfully donating $100 monthly for ten years-totaling $12,000-without completing the paper. What was meant as motivation had become an expensive subscription. This illustrates a crucial distinction: penalties intended to deter behavior can accidentally become mere prices people are willing to pay.
The phrase "carrot and stick" has evolved from its original meaning of suspending a carrot before a donkey to today's economic understanding of rewards versus punishments. These incentives help us consider how our actions affect others-like London's congestion charge making drivers account for the social cost of their driving.
Harvard economist Roland Fryer has pioneered controversial "dollars for scholars" programs to incentivize student achievement. His REACH program offered substantial cash bonuses ($500-$1,000) for passing Advanced Placement tests, while his Capital Gains program in Washington D.C. pays students up to $1,500 annually for attendance, behavior and grades. Initial results show mixed success-REACH saw 19% more top scores but no change in overall passing rates.
Poorly designed incentives can backfire, as when India's rat bounty led entrepreneurs to breed rats. But unexpected benefits can also emerge. When the FCC granted minority-owned firms a 50% bidding credit in license auctions, government revenue surprisingly increased by $45 million because traditional companies bid much higher when facing this new competition.
Unlike ordinary incentives, commitment contracts remove future options entirely. Dieters employ various disabling commitments: locking refrigerators or even gastric bypass surgery. Other commitments work shorter-term, like Antabuse, which prevents alcohol consumption by causing immediate severe nausea if alcohol is consumed.
While penalties remove options, rewards can also function as commitments. Zappos employs a fascinating commitment strategy by offering new trainees $2,000 to quit after their first week of training. This "anti-incentive" screens out uncommitted employees, signals that Zappos is a worthwhile workplace, and most importantly, increases internal commitment among those who reject the offer. By turning down substantial money, employees signal to themselves that they truly value their jobs, creating psychological motivation to succeed.
5장
Why Losses Loom Larger Than Gains
The first scientific test of commitment contracts occurred in England over thirty years ago when psychologist Robert W. Jeffrey recruited overweight middle-aged men for a fifteen-week weight loss program. The key feature: participants had to risk their own money, which they could earn back only by meeting their weight loss targets.
Loss aversion powerfully influences our decisions. Experiments show people hate giving up things they already own-from wine preferences among college students to capuchin monkeys preferring gambles where they might gain rather than lose apple slices. This aversion to loss makes stick contracts more effective than carrots. When Thaler and Kahneman gave Cornell students mugs, the students wanted more than $7 to sell them, while others would only pay $3.50 to buy them-suggesting losses loom twice as large as gains in our minds.
Kevin Volpp, an economist and physician at the University of Pennsylvania, designed weight-loss incentives that addressed the participation challenge of deposit contracts. Rather than requiring upfront deposits, Volpp created a carrot-based lottery system for overweight veterans. Participants who met daily weight goals could play in a hybrid lottery with a 1-in-5 chance of winning $10 and a 1-in-100 chance of winning $100.
After sixteen weeks, the lottery group lost 13.1 pounds versus only 3.9 pounds in the control group. However, these carrots were expensive-subjects lost only 0.05 pounds per dollar received, compared to Jeffrey's subjects who lost 3.5 pounds per dollar forfeited, suggesting the power of loss aversion as a motivational tool.
Combining rewards and punishments offers the best of both approaches. Volpp tested this with a third group who could deposit up to $3 daily of their own money, which would be matched dollar-for-dollar if they met weight goals. They also received a $3 direct payment for meeting goals and a $50 bonus for losing 20+ pounds. This carrots-and-sticks approach produced the best results-an average 14-pound loss with less variation than other groups.
In 2008, James Hurman, a New Zealand advertising executive, created commitment history by auctioning his "smoking habit" on YouTube. After establishing strict terms where even a single puff would count as a full cigarette requiring payment of NZ$1,000, Hurman relied primarily on public accountability. Though the auction closed at just $300, Hurman successfully quit smoking, reporting that unlike previous attempts, he experienced surprisingly few cravings-something about the contract itself seemed to diminish his desire to smoke.
6장
The Power of Social Accountability
In fall 2001, I tried connecting with Yale law students while getting back into running shape by offering a "charitable bribe"-$10 to charity whenever students showed up at 7 AM to run with me. The incentive worked moderately well, but student participation was surprisingly low, occurring only about a third of the time. This puzzled my economist mindset, as offering payment should have increased interest.
Uri Gneezy's research explains another factor: small bribes can actually undermine intrinsic motivation. His experiments with Israeli students showed those offered tiny amounts (3 cents per correct answer) performed worse than unpaid participants, while those offered substantial rewards (30 cents per correct answer) significantly outperformed both groups. His conclusion-"Pay Enough or Don't Pay at All"-suggests effective carrots must be substantial to work.
Rob Harrison, a beloved Yale Law School teacher, helped procrastinating students overcome writer's block by having them give him checks up to $10,000 made out to charities, which he would mail if they failed to submit papers by deadline. Initially students chose charities they liked, but about five years ago they began selecting "anti-charities"-organizations they actively opposed-creating even stronger motivation.
Remarkably, Rob never had to mail a single check despite working only with students who had demonstrated serious writing blocks. This approach creates powerful incentives by combining financial loss with potential guilt. Unlike day-care center fines that merely became prices for lateness, anti-charity commitments make small financial losses "loom large" by attaching moral weight to them.
Robert Cialdini's insights about social norms have powerful applications beyond hotel towels and national parks. By redesigning energy bills to show households how their usage compared to neighbors in similar-sized homes, we achieved a 2% sustained reduction in energy use over six months. The highest energy users reduced consumption by more than 6% when informed they were outliers, while efficient users maintained their good habits, motivated by the smiley face approval symbol.
Barry Nalebuff's commitment experiments demonstrate the power of public accountability. After his Yale class experiment, he designed a similar test for ABC's Primetime where participants risked having unflattering swimsuit photos aired on national TV if they failed to lose weight. Four of five succeeded, with the fifth losing thirteen pounds.
Public declarations can be powerful motivators-as when economics professor Justin Wolfers publicly committed on the Freakonomics blog to run the Stockholm Marathon, which he completed in 4:15. The effectiveness increases when you tell people similar to who you want to become (tell nonsmokers about quitting smoking, tell thin people about weight loss goals).
7장
The Challenge of Maintenance
Ryan Benson's cautionary tale from "The Biggest Loser" illustrates the fundamental problem with quick-fix approaches. After losing 122 pounds in twelve weeks to win $250,000, he regained 32 pounds within five days and eventually returned to over 300 pounds. His extreme methods included starvation, dehydration, and dangerous wrestling techniques that left him "peeing blood."
Unlike Benson, Andy Mayer took a methodical approach to weight loss as Express Scripts' VP of consumerology. Using a stickK commitment contract, Andy put $1,500 at risk and committed to losing one pound weekly for twenty weeks. The social accountability of telling friends and family proved crucial to his success-he lost 10% of his body weight. However, when pressed to sign up for a maintenance contract, Andy resisted, feeling he needed a break after achieving his goal.
Research shows the depressing pattern of weight loss followed by regain. A Weight Watchers study revealed participants lost an average of twelve pounds after six months but regained almost half within two years. Only about one in five successful dieters maintain their weight loss through the end of the year. People typically fail after six months because they stop paying attention-they avoid the scale after minor weight gain, then give up entirely when they discover significant regain.
Dr. Rena Wing's research at Brown's Alpert Medical School has revealed crucial insights about weight maintenance. Through her National Weight Control Registry, which tracks people who've maintained at least a thirty-pound weight loss for over a year, Wing discovered that regular self-weighing is essential for success. Her randomized "Stop Regain" experiment demonstrated that people who weighed themselves daily and tracked their weight in green (within 3 pounds of goal), yellow (3-4 pounds over), or red zones (5+ pounds over) regained only half as much weight as the control group.
Most dieters set unrealistic goals, wanting to lose 30% of their body weight when research shows maintaining more than a 10% loss is nearly impossible without surgery. Creating the illusion of progress can accelerate goal achievement. Professor Ran Kivetz proved this at a cafe where customers with a 12-stamp loyalty card (with 2 stamps pre-filled) reached their free coffee goal 20% faster than those with a 10-stamp card, despite identical requirements.
Contrary to popular belief, flexibility and commitment aren't mutually exclusive. Effective commitment devices should incorporate appropriate flexibility-whether through warning tracks, exemptions, or occasional allowances. When designing flexibility, use specific "rules" rather than vague "standards"-commit to "having a will made by June" rather than "making progress on estate planning."
8장
Commitment as Communication
Commitments serve as powerful signals to others about our intentions. When people say "I'll be brief" but continue speaking at length, they demonstrate the weakness of cheap talk without consequences. More effective commitments include specific numbers and accountability mechanisms.
Commitments serve as effective screening devices to test others' sincerity. When property manager Richard Eisner refused to offer a buy-back option on a duplex investment, his unwillingness to commit revealed his true intentions-he later abandoned the project. Similarly, a philandering husband who refuses a postnuptial agreement shows questionable commitment to change.
Doug Short, founder of BeniComp Group, transformed his personal experience with back injury into an innovative health insurance model. BeniComp Advantage offers plans that significantly reduce employee deductibles for meeting wellness goals like maintaining healthy BMI, cholesterol, blood pressure and glucose levels. In Benton County, Arkansas, deductibles were raised from $750 to $2,750, but employees could reduce them to $500 by meeting health standards. The program produced dramatic results-turning a $480,000 deficit into a $1 million surplus within a year.
Companies use commitments to signal values to employees and customers through certifications like Fair Trade and SA8000. The author and his wife Jennifer created the "Fair Employment mark" certification to promote equal employment rights for gay workers, addressing the gap between public support (88% of Americans favor equal job opportunities) and legal protection (most states still permit discrimination).
While nationwide conservation typically requires mandatory legislation like cap-and-trade, voluntary commitment systems already govern about 4% of U.S. greenhouse gas emissions. The Chicago Climate Exchange has over 350 firms bound to independently verified contracts reducing emissions 1% annually. Companies that exceed targets can sell permits; those falling short must buy them.
The Illinois voluntary self-exclusion program for gambling demonstrates how commitment contracts can effectively change behavior. When Nick Del Giudice won $20,000 at a casino in 2006, he couldn't collect because he had enrolled in the state's self-exclusion program years earlier. Casinos are legally obligated to check winners against this database before paying out more than $1,200, and can keep both the wager and winnings from self-excluded gamblers.
9장
The Ethics of Self-Binding
Shakespeare's Merchant of Venice illustrates how naivete can lead people to accept excessive commitment penalties. Antonio agrees to forfeit a pound of flesh if he fails to repay Shylock, overconfident in his ability to meet the obligation. This demonstrates the flip side of commitment contracts-unsophisticated promisors who underestimate future difficulties.
Credit card companies exploit similar cognitive weaknesses with high interest penalties that consumers don't expect to pay. Economists have shown that borrowers sometimes agree to "arm-breaking" contracts with excessive penalties to signal their reliability, creating inefficient signaling competitions.
Is risking $26,000 to maintain my weight excessive? Not compared to Curt Schilling's $2 million weight-loss incentive with the Red Sox in 2007. His contract included six monthly weigh-ins worth $333,333 each if he stayed under 230 pounds. Despite this massive financial stake, Schilling insists money wasn't his motivation.
This illustrates the "fundamental attribution error"-we blame circumstances for our own failures but blame character for others' failures. This psychological bias complicates commitment contracts, as parties may disagree about how much control someone has over outcomes.
Benjamin Franklin once "conceiv'd the bold and arduous project of arriving at moral perfection," attempting to live without committing any fault. He quickly discovered this was harder than anticipated: "While my care was employ'd in guarding against one fault, I was often surprised by another."
This experience mirrors modern challenges with commitment contracts. When I commit to watching less TV, I end up misusing the internet more. Addiction specialists recognize this as "addiction transfer"-about 25% of alcoholics who relapse switch to a new drug. The substitution problem is particularly pronounced after bariatric surgery, where 20-30% of patients develop new compulsive disorders like gambling or shopping.
Research by psychologist Roy Baumeister suggests self-control is a finite resource that can be depleted. Studies show people who resist temptation subsequently give up faster on difficult tasks. However, Baumeister also discovered that self-control can be strengthened like a muscle through regular exercise.
The key insight is that commitment contracts might reduce ego depletion by taking choices completely off the table. Unlike incentives that merely guide future decisions, commitments eliminate options entirely. When theft simply isn't considered an option, no willpower is expended resisting temptation.
10장
Building a Commitment Infrastructure
The author first met Dean Karlan in 2006-a warm, enthusiastic economist who proposed creating an internet-based "commitment store." Unlike the Money Store providing loans, this would offer one-stop shopping for people wanting to commit to real change, with standardized terms and enforcement.
Karlan's faith in commitments grew from personal experience and field experiments. In 2002, he partnered with Green Bank of Caraga in the Philippines to test "SEED" accounts that restricted clients' access to their deposits until meeting savings goals. Despite paying no higher interest than regular accounts, 28% of those offered took the commitment product.
The results were remarkable-just being offered the commitment device increased average savings by 47% after six months and 82% after a year. Those who actually opened SEED accounts saw their savings increase more than threefold compared to the control group.
After seeing Karlan's impressive results, the authors became convinced a "commitment store" could be viable. They wrote a Forbes column describing a weight-loss bond concept where dieters could earn back their deposit plus interest for meeting goals. To transform the concept into reality, they recruited Jordan Goldberg, a Yale MBA student who took leave to become CEO. After brainstorming names, they settled on "stickK"-a double entendre referencing both helping people "stick" to goals and using "sticks" rather than carrots as motivation.
The team designed the site around user autonomy-people choose their own goals, accountability mechanisms, and whether to risk money or simply notify supporters of their progress. Users also select their own referees, whose judgments about success or failure would be binding.
By August 2009, stickK had over 40,000 registered users from more than 130 countries, growing at 125% annually. Users had created over 25,000 contracts averaging three months in duration, with more than 10,000 backed by financial stakes totaling over $3 million (averaging $275 per contract).
The custom-designed contracts on stickK reveal remarkable diversity in human goals and struggles. The early results are encouraging: only about 20% of money at risk is forfeited, users report losing nearly 60,000 pounds, and the success rate for financially-backed smoking cessation contracts exceeds 60%.
All three accountability mechanisms matter: financial stakes have the biggest impact, but supporters and referees also improve outcomes. Contracts without money, supporters, or referees have less than 25% success rates, while those with two or more supporters achieve 60% success.
Looking ahead, commitment contracts are increasingly being adopted by businesses to help customers and employees change behavior. Electric companies might help customers commit to reducing bills, employers could facilitate carpooling commitments, and car dealers might assist with savings plans. Some life insurance companies already offer lower premiums to non-overweight applicants but might soon extend better rates to those who commit to staying fit or smoke-free.
While commitment devices can powerfully change lives, they also raise concerns about employers demanding credible change from employees. The future will likely see more sophisticated applications of commitment contracts with better predictive data about success factors. Though behavioral economics remains a young science, commitment contracts that consistently achieve even 50% success rates in areas like weight loss or smoking cessation could potentially save countless lives-an achievement worthy of Nobel recognition.
