Mental Representation

All representations have content; but do they typically possess other features as well? One proposal is that, for an entity to be a representation, it must also be capable of standing for its object in the absence of that object. In this case, for instance, the level of mercury in a thermometer would not represent the temperature of a room because the mercury cannot stand for that temperature in its absence: if the temperature were different, the level would change.

Even when this constraint is satisfied, different types of mental representation are distinguishable. For example, throughout the day, the sunflower rotates to face the sun. Moreover, this rotation continues even when the sun is occluded. Consequently, it stands to reason that somewhere there is a physical process that represents the location of the sun and that guides the flower's rotation during those instances when the sun is not present. However, there is very little a sunflower can do with this representation besides guide its rotation. Humans, in contrast, are not subject to this limitation. For instance, when seeing a cat, a person may represent its presence at that moment. Furthermore, the person may think about the cat in its absence. But, unlike the sunflower, that person can also think arbitrary thoughts about the cat: "That cat was fat"; "That cat belonged to Napoléon," etc. It seems as if the "cat" representation can be used in the formation of larger—and completely novel—aggregate representations. So, while possessing content is a necessary feature of mental representation, there may be additional features as well.