Why Do Drugs Make People Do Odd Things?

The short answer is that drugs alter your perceptions and your judgment. Different drugs do this in different ways. Some drugs make you overconfident, and some drugs decrease your ability to pay attention to the things going on around you, even when those events are critical to your health and safety (like seeing a red light while driving). Other drugs, like LSD, can change your perceptions so much that you can't recognize people and things in your environment at all.