Distinctions Between Visual Sensation And Visual Perception example essay topic

Visual sensation differs from visual perception even though the two processes form a sequence. Our brain obtains meaning from what we look at through the process of sensation and perception (Grivas Down & Carter pg 77). Though the two systems interact they both serve a different purpose. Sensation is a physiological process which involves the " reception and transduction of information and its transmission to the brain". (Grivas Down & Carter pg 77). In other words sensation involves collecting the sensory data, converting it to electromagnetic energy and sending this information to the brain.

After the sensation process comes perception". Perception is a mental process of organising sensations into meaningful patterns". (Coon glossary pg 15). Visual perception is influenced by emotional states, motivation and many other psychological factors. So visual sensation is the organisation of the information our sensory receptors receive, and visual perception is the organising and interpreting of the sensations. This shows the distinctions between visual sensation and visual perception.

The above demonstrates that the sensory system receives the same data via the sensation process but each individuals perception system interprets it differently. An example of this might be when my mother and I go shopping together. She usually wants me to buy things that she likes but I generally think they look disgusting. Even though we are both looking at the same thing we both have different perceptions of what is fashionable. There are several visual perception principles which play part in the way we perceive things. One of these is size constancy.

Size constancy is something we must learn through our life experience. Size constancy occurs when " The perceived size of an object remains the same even though the size of the image it casts on the retin changes". (Coon pg 120). An example of size constancy might be when flying in a plane. When I look out the window and view the world below if I were to look at a house it would look to be the size of a small dot.

I know, Through the principle of size constancy that the house hasn't shrunk. So my brain draws on past experience to help me perceive the house accurately. Empirical research indicates that size constancy is something that is learned. This is supported by Colin Turnbull's experiment (Coon pg 120-121). Turnbull took a pygmy from his home in a dense rainforest. An environment which was so dense that the pygmy would never have been able to perceive things from the distance.

When taken to the vast African plains the pygmy identified a herd of buffalo in the distance to be a swarm of insects. As the pygmy went towards the 'swarm' he discovered they were buffalo's. Turnbull concluded that the principle of size constancy is learned. One has to question the validity of this experiment however as it is based on only one person. Depth cues are another type of perceptual principle. Several depth cues combine to help us perceive three dimensional space.

(Coon pg 125). Convergence is a binocular depth cue, it's " the simultaneous turning inward of the two eyes as they focus on nearby objects". (Coon glossary pg 5). When we look at an object such as a tree in the distance our eyes don't need to converge to focus on it. This is because our lines of vision are almost parallel. However, if we want to focus on something closer, for example a piece of paper our eyes must converge in order to focus.

Convergence shows the relationship between muscle sensations and distance. (Coon pg 126). Convergence occurs naturally and it's something that we are generally unaware of. A group of muscles attached to our eyes control convergence". These muscles feed information of the eye position to the brain to help it judge distances".

(Coon pg 126). Another depth cue is interposition. This is a perception principle we use frequently". Interposition refers to the fact that an object which is close to us will bock or obscure something which is further away". (Clarke & Gillet pg 105). An example of this might be if we were looking at a tree.

If someone were to stand next to the tree we would not know which of the two were closest to us. If that person were to stand in front of the tree however, our depth cues would tell us through the principle of interposition that the person is closer. We would also know that the part of the tree that is partially obscured has not disappeared". There are many other mental factors which can affect the way in which our sensory information is interpreted". (Grivas Down & Carter pg 86). Therefore these factors effect our visual perception of things.

These psychological factors are things such as prior experience, expectancy, attention, motives, habituation and hypothesis testing. It's these factors which help to create the individual differences in perception between people. One psychological factor which effects our perception is hypothesis testing. The sensory information our brain receives is sometimes hard to interpret. When this occurs our brains make an educated guess or a perceptual hypothesis as to what we are seeing. (Clarke & Gillet pg 88).

An example is when I see a friend in the distance, but as they move closer I discover they are a stranger. This occurs because "Pre-existing ideas and expectations actively guide our interpretation of sensations in many situations". (Mc Burney & Collings Coon pg 123). Another psychological factor which can effect our perception is perceptual expectancy.

We have a tendency to perceive what we expect to perceive. Some things may be perceived in a certain way due to motives, past experience or suggestion. (Coon pg 138). These are the factors which contribute to produce a perceptual expectancy. Empirical research conducted by Gordon Allport demonstrated how our perceptions and memories can be effected by our prejudices or what we expect.

Allport briefly showed a picture to a group of people, one of the people in this picture was black. When the people looking at the picture were asked who was holding the razor, fifty percent identified the black man. This experiment shows that factors such as perceptual expectancy and prejudice play a role in determining what we see. (Lahey pg 510). Expectancy can cause fallibility in our perceptual judgement. Fallibility could be defined as the susceptibility for something to fail.

Our visual perceptual systems quite commonly tend to fail us in one way or another. I think a good explanation of the fallibility of visual perception can be shown through illusions. An illusion is a "discrepancy between what a person perceives and the real world". (Clarke & Gillet pg 306).

Illusions demonstrate how we use several sensory cues to create a perceptual experience which may or may not correspond to what we are really sensing. (Clarke & Gillet pg 108). Illusions are one example of visual fallibility. Sometimes we see unreal or misleading impressions and our perceptual systems fail to accurately represent these. An example of visual perceptual fallibility is the moon illusion. Empirical research conducted by Kaufman and Rock in 1989 dealt with this illusion.

(Summers pg 177). Kaufman and Rock noticed that the moon always appears larger when it's near the horizon than it does when its in the sky. Although the size of the moon remains the same our perception of it changes. This occurs even though our distance from the moon and the image it casts on the retina remains the same.

The moon appears larger when its on the horizon due to the surrounding depth cues. Things such as houses and buildings can add depth cues to the horizon. In contrast there are few depth cues in the sky. These depth cues cause the horizon to appear farther away which leads us to perceive that the moon is larger. So even though the moon remains the same size many psychological factors and principles play part in the perception or misconception of its size.

This clearly illustrates one way in which our eyes are fallible in that they can misinterpret sensory information directly effecting our perception. This essay clearly shows the distinctions between visual sensation and visual perception. It does this by showing that visual sensation is a physiological process whereas visual perception is a psychological process. It clearly explains several visual perception principles illustrating the way in which they play a part in the way we perceive things.

It explains the influences psychological factors can have on our perception and how these factors play part in the susceptibility for our perception systems to fail. Relevant empirical research has been included to substantiate the information presented. word count- 1437 31 e.