Security is more than filtering input and escaping output (FIEO), and it’s more than cross-site scripting (XSS) and cross-site request forgeries (CSRF). Security isn’t even always black and white. In order to create a more secure user experience, we need to understand how people think. Perception is as important as reality, and meeting user expectations is a fundamental of good security. In this multifarious talk, I’ll introduce some of what I have learned about cognitive psychology, exploring topics such as change blindness and ambient signifiers, and I’ll show some real-world examples that demonstrate the profound impact human behavior can have on security.