The different theories of perception are adverbial theory, disjunctivist theory, self-perception theory and visual perception theory. Perception is a person's ability to be aware of and understand what is happening in his or her environment. The theories of perception have developed around the way the mind processes information that the sensory organs — the eyes, ears, nose and skin — send to it. These organs send signals to the brain, which uses them to create memories, make decisions and reflect on problems. The different types of perceptions included in the theories of perception are hallucinations, veridical perceptions and optical illusions.
Hallucinations are sounds, sights or physical feelings of an object that the mind produces, even though there is no such object in the environment to trigger these perceptions. Veridical perceptions are perceptions that are true by seeing or sensing an object that does exist, with the same characteristics that it actually has. Optical illusions make objects appear to have different characteristics than the ones that they actually have.
Adverbial theory simplifies the concepts behind appearances as related to the theories of perception in order to explain the process of how people perceive or see things. According to adverbial theory of perception, when an object appears to be a certain color, the color is considered to be an adverb. Color describes how the object appears and how it makes an impression on the mind.
Perceived characteristics are not made by the object; they are interpreted by the mind. Interpretation of an object's appearance takes place within the mind's justification or reasoning of why the object appears as it does. The way that a person perceives the object and its characteristics is how it appears to him or her. If the object has parts that a person cannot see or perceive, those parts will not appear to him or her.
Disjunctivist theory states that perceived objects are mind-independent. When a person perceives his or her environment, the mind-independent objects constitute his or her experience. Veridical perceptions involve mind-independent objects, or objects that exist in the environment. Hallucinations have mind-dependent objects; they are perceptions of objects that do not exist in the environment. During a hallucination, the objects that are perceived are not really there and do not represent what is perceived.
Self-perception theory is the theory of self-awareness. A person creates an attitude or belief of another person's attitude during a situation through observation and reflection of the causes of his or her own behavior. The person believes that his or her own attitudes, inner feelings and abilities are derived from his or her external behaviors, or the way in which he or she interacts with the world. Self-perception theory developed as an explanation for cognitive dissonance, which is when a person believes two contradicting ideas at the same time. This causes discomfort, so a person is most likely to believe that his or her own choice is correct, even in the face of evidence that proves otherwise.
Visual perception theory includes two main theories: Gibson's theory and Gregory's theory. Gibson's theory, which was named after American psychologist James J. Gibson, is called bottom-up processing, and it states that perception of an object begins with visual stimulus. The eye sees the object and sends this information to the visual cortex of the brain, where the object is interpreted and identified by the mind. British psychologist Richard L. Gregory's theory of top-down processing deals with the mind's ability to interpret information and patterns in a given context. A person can identify an unintelligible, hand-written word by reading the entire sentence that it is in — the context or meaning of the other words in the sentence is used to give the unintelligible word meaning.