There is a phone app called StickK that was founded by economics professor Dean Karlan at Yale University. He wanted to open an online “Commitment Store.” He envisioned that people would come to the Commitment Store to sign contracts obliging them to achieve their personal goals, such as losing weight or quitting smoking. Standard economic theory assumes that people have self-control. So why is this app important to people, and what do behavioral economists believe are the flaws of conventional economic theory when it comes to self-control? Would a penalty help people keep their commitment?