This lecture comes from Yale's course Understanding Medical Research: Your Facebook Friend is Wrong, part of a series aimed at teaching viewers to spot flawed reasoning in health claims that circulate online. Here the instructor runs through thirty brain teasers, short puzzles designed to expose common errors in logic, probability, and statistical intuition, the same errors that make misleading medical claims sound convincing. Each teaser sets up a quick problem, lets the viewer guess, then walks through why the intuitive answer is often wrong. The exercise builds toward the course's larger point: that recognizing these mental shortcuts is the first step to evaluating a study or a headline critically. At nineteen minutes, the lecture moves briskly through the puzzles rather than lingering on any single one, functioning as a warm-up drill for the more detailed methodology lectures elsewhere in the course.