Persuasion design uses techniques from psychology and behavioral science to lead people to measurable changes in behavior. It involves understanding motivation and ability, and placing triggers in the path of motivated people. Common motivation boosters used include social proof, scarcity, reciprocation, authority, liking, and commitment. Ability boosters help make the desired behavior easier, such as through mobile devices, micro-payments, or simplicity. Triggers aim to activate people when they are motivated and able, using techniques like social networks, retargeting, and smart banners. Testing and optimizing persuasion designs is important.