Researchers Katherine Milkman, Julia Minson and Kevin Volpp conducted an experiment involving 226 participants to explore how incentives shape workout habits. Their 2013 study, later published in Management Science in 2014, examined whether restricting access to engaging audiobooks to the gym environment would encourage more frequent visits.
The trial divided participants into three groups: one could access audiobook-loaded iPods exclusively during gym sessions, another received audiobooks with encouragement to listen only while exercising, and a control group received neither. The gym-only cohort initially attended 51% more frequently than controls. However, this advantage eroded noticeably, particularly following the Thanksgiving break. The researchers emphasised this represented an early attendance spike rather than a sustained 51% increase throughout the study or evidence of lasting fitness gains.
Pairing pleasure with purpose
The approach demonstrates temptation bundling—combining something immediately gratifying with an activity whose payoffs may seem distant. Rather than treating entertainment as a post-workout reward, the audiobook became integral to the gym experience itself.
This timing distinction carries practical weight. Promising a reward after completing a month of workouts requires patience. An absorbing narrative, by contrast, enhances the appeal of each individual session. Success hinges on both elements: participants must genuinely desire the entertainment, and the activity must permit them to enjoy it. Milkman highlighted the difficulty of maintaining initial momentum and re-engaging participants after extended absences. The university population studied had already expressed motivation to exercise more—a significant characteristic of the sample.
The holiday interruption as a diagnostic moment
An intervention can improve early decisions without establishing a durable habit. Holidays disrupt schedules, locations and access to the supporting elements that enabled those decisions. When effectiveness changes after such a break, it provides meaningful insight into whether benefits persist.
This does not constitute a rigorous experiment on holiday effects alone; isolating the break's impact from simple time passage would require appropriate comparison groups. The reasonable conclusion is that the initial advantage weakened, with the interruption marking a notable inflection point in that decline.
For teams developing behaviour-change products, this underscores the importance of measuring beyond launch windows. The opening week, the subsequent month and the return following an interruption may expose distinct challenges. Initial engagement and successful re-entry warrant separate evaluation, even within a single service.
A broader test with relaxed constraints
A 2020 field experiment involving 6,792 participants in a four-week exercise program tested a modified version. Participants either received an audiobook paired with guidance to combine listening and workouts, an audiobook alone, or nothing.
The audiobook-plus-guidance condition raised the probability of a weekly workout by approximately 10% to 14% and boosted average weekly workouts by roughly 10% to 12% across the program and a seventeen-week follow-up period. The incremental value of explicitly teaching temptation bundling versus simply providing an audiobook proved modest. Researchers suggested a likely explanation: offering an audiobook within an exercise context may inherently signal that listening during workouts is appropriate.
This intervention differed fundamentally from the original university gym setup. Allowing participants to self-impose listening rules scales more readily but grants them freedom to listen elsewhere. The later study tested this less restrictive model rather than replicating the original arrangement.
Recovery from lapse as a separate challenge
A 2021 Nature megastudy examined 54 distinct four-week digital programs across 61,293 members of an American fitness chain. Forty-five percent of the interventions produced statistically significant increases in weekly gym attendance, with reported improvements spanning 9% to 27%.
The highest-performing intervention offered modest incentives for returning after a missed session. This finding highlights recovery from lapses as a distinct behavioural target, separate from making the activity initially appealing.
The result does not confirm whether the same incentive would have prevented the audiobook trial's decline. The studies involved different populations and programs. Collectively, however, they demonstrate that initiating habits, sustaining them and restarting after interruption constitute separate behavioural challenges requiring tailored approaches.
Measuring what actually changes
A gym visit represents a concrete, measurable outcome. It reveals nothing about workout duration or intensity and cannot independently demonstrate health improvement. Transparent reporting maintains a distinction between the measured action and the hoped-for consequences.
This principle extends beyond fitness. An app launch, a completed lesson and retained knowledge are distinct outcomes. A product may shift one without proving the others. Evaluating an appealing pairing requires deciding upfront which behaviour matters and verifying whether effects endure. The audiobook research suggests a specific mechanism: activities people already intend to pursue become more attractive when accompanied by something enjoyable. Its declining effect poses a practical question for any implementation: what motivates return when the routine breaks?
Source: Silicon Canals
