Visual Illusion

In a word, yes. Conceptually driven processing is also referred to as top-down processing. It refers to the dependence on prior knowledge or our expectations concerning the incoming stimulation. An example of when conceptually driven processes are in action is when we see a face. Once the image has entered the eye our previous built up knowledge of human faces can guide us into actually recognising the image as a face.

Therefore ‘conceptually driven processes uses a higher level of conceptual processes which include such things as memories of past experiences, general organisational strategies, knowledge of the world and expectations based upon the surrounding context or situation’ Coren, Porac and Ward (1978). Having said that, there is another process which takes place in visual perception other than conceptually driven processes. You can not talk about conceptually driven processing without mentioning data driven processes. Data driven processes can also be known as bottom up processing. This basically refers to the stimulus input having a direct affect.

This stimulus drives a series of analysis’s and the looking for distinctive features e. g. shape, colour, size etc. It is often believed that both conceptually driven processes and data driven processes work together. Conceptually driven processing uses many types of information to interpret what is being observed. One such thing is context. A good study which helps demonstrate the role of conceptually driven processes uses context. Mandler and Parker (1976) showed participants a picture of a living room. Later on the same participants were asked to reconstruct the picture they had seen earlier but were now scrambled.

This was an easy task to perform. However, Mandler and Parker (1976) also asked to participants to reconstruct the scrambled picture having not seen the earlier unscrambled image. Even though they had not seen the original image they all managed to reconstruct the picture correctly. Mandler and Parker (1976) argue this reflects the use of conceptual framework based upon our experience with real world scenes. However this is just an example of looking and reconstructing something that we are used to and have seen many times. It is intriguing to find out what processes take place when a visual illusion is being observed.

People’s perceptions are called illusion when they experience a stimulus pattern in a manner that’s seems incorrect. For example when you look at the Hermann grid (appendix 1) you begin to see fuzzy spots that are not there. It is suggested that our knowledge can not overcome the illusion, because it operates at a more basic, sensory level. Therefore when you look at the image you start to use your conceptually driven process which is not what is needed in order to stop seeing the ‘fuzzy’ spots at the intersections. This is therefore an example of data driven processes and thus demonstrates the importance of data driven processes.

Visual illusions demonstrate to us that the central nervous system does not simply record events. The system, instead, involves complex processes for ‘detecting, integrating and interpreting information about the world in terms of what we already know and expect’, Zimbardo, McDermott, Jansz and Metaal (1995). This therefore shows that what we see goes beyond the present physical stimulus properties. Even though these processes usually occur without effort and are also helpful in decoding the world around us does not mean that they are simple and error-free.

Conceptually driven processes do succumb to errors. Our knowledge and previous experience can in fact fool us into seeing what does not exist. A good example of this is the Kanizsa’s triangle (appendix 1). It is an example of illusory contours whereby we see something that does not actually exist. The circles have indents of 45 degree angles and there is a broken outline of a triangle this gives the illusion of another triangle. We try to make sense of the images by trying to look for something we are familiar with.

Our past experience and knowledge of what a triangle looks like makes us see a triangle in this image, thus we have made sense of it. Coren (1972) Coren and Porac (1983) argue that we create the subjective contours because we see simple, familiar figures in preference to meaningless, disorganised parts. The simple figure in the illusion being the triangle that does not exist. If we did not see this triangle the illusion would be meaningless to us, yet our conceptually driven processes constantly seek understanding of an image.

A British psychologist, Richard L. Gregory studied a man by the name of S. B.in the 1960’s. S. B. had been given the gift of site after spending all his life blind, having been born that way. Gregory wanted to look at how S. B. perceived things for the first time as babies, who also experience sight for the first time can not help to explain what they see. It was interesting to find that S. B. failed to be misled by illusions such as the Herring illusion, (appendix 1). This suggests that he was only looking at the stimulus input and obviously could not look to knowledge and past experience to understand the image. It must mean the conceptually driven processes are learned rather than innate.

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