Behavioral Design: Making People Predictably Better
Kristen Berman
CEO & Co-founder, Irrational Labs
BEHAVIORAL SCIENCE
Foundation
The 3 Bs of Behavior Change
"People make decisions with lots of emotion. We are present bias. We follow social norms. But the good news is we do these things in predictable ways."
Motivation: Does the user want to do this? Are they actually thinking about the benefits?
Barriers: What logistical and cognitive friction prevents them from doing it?
Benefits: Are the benefits immediate or delayed? Immediate wins drive action today.
Case Studies
Real Impact from Behavioral Design
24%
less misinformation shared (TikTok)
53%
purchase rate increase (TytoCare quiz)
133%
conversion boost (Trunk Club)
TikTok: Slowing Down Sharing
Added unverified label + "Are you sure?" popup at share moment. Reduced misinformation shares by 24% by interrupting the hot state and making people reconsider.
TytoCare: Quiz Engagement
Instead of carousel benefits, asked medical behavior questions during signup. 53% of quiz completers purchased vs. 37% who didn't. Active engagement drives motivation.
FinTech Surprise
Budgeting feature had zero impact on spending despite being top user request. Behavioral diagnosis revealed too many steps. Defaults would work better.
Credit Karma
Helped increase auto-deposit setup by 18% through reducing cognitive load. Defaults and rules of thumb beat features that require active decisions.
Playbook
How to Apply Behavioral Design
Do a behavioral diagnosis: Map every step your user must take. If it's too many steps, the behavior won't stick.
Ask questions, not carousels: Get users actively thinking about benefits. Multiple-choice questions beat open text fields.
Reduce, don't add: To decrease a behavior (like sharing misinformation), add friction. To increase, remove it.
Time matters: Friction should interrupt hot states. Benefits must be immediate, not delayed.
Budgeting paradox
Users requested budgeting. The team almost built it. But 10K user test showed zero impact. Why? Too many cognitive steps. Design for what users actually do, not what they say.
Rules of thumb
Instead of "should I take Lyft today?", use a rule: "I take Lyft on weekends only." Simple heuristics stick. Complex decisions don't.
The Dark Side
Getting Incentives Right
You become what you measure. LendingClub incentivized conversions, which made Kristen almost a predatory lender.
Measure behavior, not vanity metrics. Behavior aligns better with customer outcomes than retention or DAU.
Extend the time horizon. Quarterly targets breed short-term exploitation. Annual targets align with customer good.
The LendingClub lesson
Incentive: $$ for 5-point conversion bump. Result: Kristen suggested predatory tactics. Legal team said no. She hit 4.5 points anyway. Almost sold her soul. Incentives drive behavior—yours AND your users'.
Contrarian
What Behavioral Science Actually Says
✗Give people features and they'll use themINSTEAD →✓ Test with real users first. Budgeting was top request but had zero impact. Ask, don't assume.
✗Lower friction always increases conversionINSTEAD →✓ Adding friction can boost conversion if it makes users think about benefits. Questions beat carousels.
✗Behavior change comes from mindset shiftsINSTEAD →✓ Behavior drives identity, not the reverse. You become a person who does things by actually doing them. Redesign environments, not attitudes.
✗Behavioral tactics are manipulativeINSTEAD →✓ The ethics depend entirely on your incentives. Set the right KPIs and behavioral science becomes pro-consumer alignment.