Gestalt theory proposes that people perceive objects and visual stimuli as unified wholes, rather than merely as a collection of individual parts. The psychologist Max Wertheimer developed Gestalt theory in 1910, noticing that visual meaning can change depending on cognitive interpretation. There are four principles of Gestalt theory: emergence, where separate pieces are comprehended as a whole; reification, where meaning is constructed from stimuli; multistability, where the brain can interpret the same image in different stable ways; and invariance, the ability to recognize connections between changed or distorted images. Together these principles help explain how people derive meaning from visual information.