Kristen Berman (00:00): Economics says, "Look, people are rational. We make decisions with no emotion. We use lots of computational energy, weigh the pros and cons." I mean, obviously, that's just not true. It ignores the whole field of psychology. And so, in behavioral economics, you combine the field of psychology and economics and say, "Look, people make decisions with lots of emotion. We are present bias. We over-weighed our present selves. We follow social norms." But the good news is that we do these things in predictable ways. And once you understand how and why people behave, you can start to change it. And so, behavioral science and behavioral design basically uses those insights on psychology to actually apply it within real world problems. Lenny (00:45): Welcome to Lenny's Podcast. I'm Lenny, and my goal here is to help you get better at the craft of building and growing products. I interview world-class product leaders and growth experts to learn from their hard one experiences building and scaling today's most successful companies. Today, my guest is Kristen Berman. Kristen is the CEO and co-founder of Irrational Labs where she and her team use behavioral science to help companies like Google, Airbnb, PayPal, Microsoft, Fidelity, and TikTok build better and more successful products. Lenny (01:15): In our conversation, we cover a ton of real-life examples of product changes that have her and her team helped craft that led to significant impact at the companies. We talk about what biases and psychologies they find most commonly get in the way of people achieving what they want achieve in your product, her biggest surprises and insights about human psychology and how it relates to product design, a couple of real-life case studies including our work with TikTok and the change they made in the product as a result, and so much more. I found this conversation super fascinating and super tactical, and I can't wait for you to hear it. And so with that, I brin...