Introduction

We usually experience the world as meaningful objects, voices, and events. We see a door rather than a collection of edges. We hear a sentence rather than a series of separate noises. This experience depends on perception.
Perception is the process of organizing and interpreting information from the senses. It uses incoming information together with context and what we have learned before.
This combination is usually helpful. It allows us to understand a partly hidden object or follow speech in imperfect conditions. It can also lead us to mistake a reasonable first interpretation for something we established directly. Understanding the difference helps us decide when a second look is worthwhile.