The principle of similarity means that consumers tend to group together objects that share physical characteristics; as an example, Coca-Cola, Sprite, and Dad's Old-Fashioned Root Beer are all "carbonated soft drinks."

The principle of similarity is a gestalt psychology principle that states individuals tend to perceive elements as grouped together if they share similar attributes. In the example given, Coca-Cola, Sprite, and Dad's Old-Fashioned Root Beer are grouped together because they share the physical characteristic of being carbonated soft drinks.