#798 2014 · Katherine Milkman, Julia Minson & Kevin Volpp (University of Pennsylvania) · Behavioral science / health & wellness
Milkman made people crave the gym by locking their favorite guilty-pleasure audiobooks inside it
the problem
People who genuinely want to exercise more still skip the gym because the payoff is delayed and willpower alone keeps losing to competing pulls
background
By the early 2010s, decades of research on self-control had converged on two levers for getting people to do a 'should' behavior like exercising: give them a reason to want it more (education, social pressure, reminders) or make skipping it cost something (commitment contracts that forfeit a deposit, fines, public accountability). Both levers fight the same uphill battle, because the should behavior's benefits are real but distant, while the pull away from it — the couch, a show, a snack — is immediate and needs no willpower at all.
Milkman had noticed the asymmetry in her own life: she only let herself listen to page-turner novels like The Hunger Games while at the gym, and found herself wanting to go. But nobody had studied whether deliberately withholding an already-loved indulgence except during a should-behavior actually created new motivation, or whether it was just a personal quirk that happened to work on her — and no version of the standard commitment-device literature, built around penalties for failing to show up, tested rewarding presence with something people already craved.
what everyone would do
The standard playbook for a self-control problem is to add a reward for compliance or a penalty for lapses — a bonus, a public leaderboard, or a commitment contract that forfeits money if you skip the gym — all of which try to make the should-behavior itself more rewarding or its avoidance more costly.
what they saw
Milkman saw that the fight didn't have to be between the should-behavior and the temptation at all — the temptation could be moved inside the should-behavior's walls, so getting the thing you already wanted required doing the thing you were supposed to want.
the move
Milkman, Minson and Volpp ran a nine-week field experiment with 226 university gym members who all said they wanted to exercise more. One group received iPods loaded with four tempting audio novels of their choice, but the devices only worked at the gym; a second group got the same audiobooks to keep but was merely encouraged to save them for gym time; a control group got a $25 gift card of equivalent value. The intervention didn't add a reward for going to the gym or a penalty for skipping it — it physically locked an already-desired pleasure inside the should-behavior, so wanting the story and wanting to work out became the same want.
why it works
Locking the audiobook to the gym doesn't change how much anyone values exercise; it changes what unlocks the reward people already crave right now, and immediate cravings reliably beat delayed benefits in every self-control study. Because the 'want' and the 'should' now share a single access gate, the same impulsive pull that used to compete with the gym now walks a person to it, and the effect requires no external enforcement — nobody has to check attendance or collect a forfeited deposit, the restriction does the work by itself.
the payoff
Participants with gym-only audiobook access visited the gym 51% more often than the control group and 29% more than the group merely asked to self-restrict — a gap that persisted, if weakened, through a Thanksgiving-week attendance crash that hit all three groups. After the study ended, 61% of participants chose to pay (an average of $6.91) to keep gym-only restrictions on their own iPods, revealing real demand for a device that took choice away from them on purpose.
where it breaks
It only works when there's a genuine, specific 'want' activity strong enough to motivate someone, one that can actually be gated behind the should-behavior (many temptations — snacking, social media, TV in general — can't be physically restricted to a single location or device). The effect also decays: attendance gains shrank over the nine weeks and cratered further during a holiday-week disruption, so bundling boosts a habit's early formation more reliably than it sustains one indefinitely, and it needs a genuine want-behavior devoted enough that its absence outside the should-behavior is actually felt, or the lock doesn't bite.
what came after
The paper coined 'temptation bundling' as a named academic concept in Management Science (2014) and launched a research program: a 2020 field experiment (with Aline Holzwarth and Angela Duckworth) replicating the design with podcasts found the exercise gains persisting 17 weeks after the intervention ended, and the concept is now taught alongside commitment devices in behavioral-economics courses and cited across corporate-wellness and habit-design programs.
references
- [1]Using 'The Hunger Games' to Encourage Healthier ChoicesKnowledge at Wharton, University of Pennsylvania, 2014knowledge.wharton.upenn.edu
- [2]An Evaluation of Temptation BundlingNational Bureau of Economic Research (Roybal Center project record), 2014nber.org