Motivating Uncertainty

Rewards motivate—or so the conventional wisdom goes. The clearer the prospect of gain, the stronger the motivation should be. That's why companies rely on guaranteed bonuses, fixed discounts, and certain benefits. Yet customers often show only moderate engagement. This raises an intriguing question: Can uncertainty about a reward motivate more strongly than certainty—and what does the evidence tell us?

Studies

The Facebook Likes Experiment

Luxi Shen and Christopher Hsee conducted a groundbreaking study at the University of Chicago in 2017. They sent 150 Facebook users notifications about new likes on their posts—either with an exact number ('3 new likes') or with uncertain information ('2-4 new likes'). The researchers measured how quickly users opened the app and how long they remained engaged. The surprising result: users who received uncertain information opened the app an average of 27% faster and spent 41% more time checking their likes. The uncertainty—even with minimally different numbers—increased engagement significantly more than certain information.

The Voucher Uncertainty Experiment

Suzanne Shu and Ayelet Gneezy tested this effect on 342 consumers at UCLA in 2010. All participants received a café voucher—Group A received a guaranteed $2 discount, while Group B received an uncertain discount ranging from $1 to $3 (averaging $2). The researchers measured both redemption rates and additional purchases. The redemption rate for the uncertain reward was 48% higher than for the guaranteed discount. Even more striking: customers with uncertain vouchers spent an average of $2.87 more than the control group. The uncertainty not only increased motivation to redeem the voucher but also raised the average basket value by 31%.

Principle

Which principle for Customer Experience Design can be derived from this? Strategic uncertainty about rewards increases engagement more than guaranteed benefits because the human brain is evolutionarily wired to respond to unpredictable stimuli with heightened attention. In customer experience, this means that elements of surprise and the unknown—whether in product discovery, reward programs, or service experiences—trigger significantly stronger emotional responses than completely transparent offers. However, this mechanism only works optimally when a fundamental foundation of trust with the company has already been established and the uncertainty is perceived as positively exciting rather than threatening. The following guidelines show how to implement this principle in practice.

Guidelines

Mystery Rewards Instead of Fixed Bonuses

Replace predictable rewards with surprise elements within a defined value range. Instead of offering "10% off your next purchase," try "10-20% off—discover your discount at checkout." This uncertainty maintains customer engagement throughout the entire journey. Important: The value range must be compelling—the minimum discount should at least match what customers consider a fair baseline.

Gradual Revelation in Loyalty Programs

Design loyalty programs with uncertain but bounded reward tiers. Instead of "Collect 100 points for reward X," use "Collect 100 points for one of three surprise rewards—valued at €15–25." Show the possible categories but not the exact reward. The uncertainty about the specific item increases engagement during the collection phase and transforms redemption from a transaction into an exciting moment.

Keep potential upgrades uncertain

Communicate potential additional services as possibilities rather than guarantees. Instead of saying "You will definitely receive a room upgrade," phrase it as "Subject to availability, we will check for a complimentary upgrade for you." This uncertainty heightens anticipation and makes an actual upgrade feel like a more rewarding positive experience. Critical: The probability must be realistic (at least 30-40%); otherwise, uncertainty transforms into disappointment.

Variable Rewards in Engagement Mechanics

Variable Rewards in Engagement Mechanics For engagement activities (quizzes, challenges, and interactions), integrate variable reward structures. Instead of "Answer 3 questions and receive 50 points," use "Answer 3 questions and receive 30-100 points based on performance." The uncertainty about the exact outcome sustains attention throughout and makes repeated participation more appealing. Important: Evaluation criteria must be transparent so that uncertainty isn't perceived as arbitrary.