The major issues which the different theories attempt to resolve are: whether our awareness of the worlds objects is determined by information presented to the sensory receptors, so we perceive things in a direct way based on sensory information (bottom-up processing); or whether perception is the end result of a process which begins with the sensory information so we perceive indirectly drawing on our knowledge and expectations of the world (top-down processing) (Gross, 1996).
Gregory (1972 and 1980) associates himself with top-down processing. The essential idea portrayed by Gregory is that perception is constructed. From a constructivist approach, Gregory argues that perception is built up starting with sensory information, which is then added to our knowledge and experience.
It is obvious that we start with sensory information, but this is only the beginning. According to the top-down theory it is our brain which is used to make sense of what we see. Gregory claims that sensory information alone is insufficient for making perceptions.
A problem identified with this theory is that we are nearly always correct in our perceptions, but the top-down theory suggests that we are always hypothesising thus we should expect more errors in our perception.
Constructivists use the retinal image as a starting point for explaining perception. Gibson (1966 and 1979) disagrees with this arguing that “it is better to begin by considering the input as a pattern of light extended over time and space which can which can be thought of as an optical array containing all the visual information from the environment striking the eye”. (Gross and McIlveen, 1997 pg23) Gibson claims that sensory information arriving at the retina contains sufficient information which enables us to make sense of what we perceive. (Twinning, 1998)
Gibson’s theory however has many flaws arguably because it is an old theory. Other psychologists have claimed that he is not explicit in all the concepts that are used. It is argued that perception is much more complex than Gibson explains. For example he does not explain why we are fooled by optical illusions.
A general conclusion on the bottom-up and top-down debate is that perception is explained by both bottom-up and top-down rather than one or the other.
The Gestalt view has been very influential within the psychology of perception. Gestalt is a German word with the nearest translation being “whole” or “form”. Gestalt psychologists attempt to discover the principles through which sensory information is interpreted. They are intrigued as to how our mind organises sensations into perceptions. Gestalt psychologists aim to show that the perceived whole is more than the sum of its parts. If we are given a cluster of sensations, the human perceiver organises them into a gestalt (whole) (Myers, 2000).
In gestalt psychology we think of all those things making up the whole: figure and ground; similarity; proximity; continuity; connectedness and closure.
According to gestalt psychologists’ the first perceptual task is to recognise the object or figure and distinguish it from its surroundings (ground).
Once we have differentiated the figure from its ground, then it needs to be organised into meaningful form. Our minds follow certain rules for grouping stimuli together (Myers, 2000). Gestalt psychologists claim that these rules illustrate that the perceived whole is more than the sum of its parts.
According to gestalt psychologists we perceive complex shapes in their simplest form, for example we perceive smooth continuous lines rather than discontinuous patterns (continuity), when linked together we perceive spots or lines as single units (connectedness) and we also fill gaps to make objects complete (closure). For example a shape with a broken, dotted or discontinuous line may be perceived as a whole continuous figure (Vernon, 1965).
Further research from Gestalt psychologists’ illustrates that our brains do more than merely register information about the world.
When perceiving depth we use binocular cues such as stereoscopic vision and monocular cues such as relative size, gradient of texture, superposition and height of field, to transform 2D retinal images into 3D. Within motion perception the brain computes motion as images move across or towards the retina. Size, shape and lightness constancies describe how objects appear to have unchanging characteristics despite their distance, shape or motion.
Visual illusions provide an example of how we go beyond the information that we are given, whereby what we perceive may not be physically present in the stimulus (Gross, 1996).
Philosophers have debated the extent to which the origins of our perceptual abilities are nature or nurture (Myers, 2000). Immanuel Kant (1724-1804) claims that knowledge comes from our inborn ways of organising sensory experiences. John Locke (1962-1704) on the hand argued that our experience helps us to perceive the world.
Philosophers such as Kant and Locke, look at how important our experiences are and how radically they shape our perceptual interpretation.
The transformation from sensation to perception can also be explained in terms of perceptual schemas, which can be defined as knowledge which is associated with a place or an event, often based on what you would expect to find in a given setting. Our schemas provide us with preconceived expectations which operate in a ‘top-down’ way in order to help us interpret ‘bottom-up’ information reaching our senses. Schemas are seen as being useful as they make the world more predictable however they can lead to distortions, for example optical illusions.
It is clear from this essay that perception is an important aspect of psychology. Referring back to the question “discuss the extent to which human perception is a product of the mind rather than sensation”, it is evident that both perception and sensation are important factors but we cannot have one without the other. This essay shows that without sensation we would not be able to make sense (perceive) the world around us. Thus it is apparent that perception is more than the sum of its parts.
References
Myers, D, G. (2001) Psychology sixth edition. Worth Michigan
Richard, G. & McIveen, R. (1997) Cognitive Psychology. Hodder & Stoughton
Twinning, K. (1998) Success in Psychology. John Murray Publishers LTD
Vernon, M. D. (1965) The Psychology of Perception. University of London Press LTD
Gross, R. (1996) Gross Psychology: The Science of Mind and Behaviour, Third Edition. Hodder and Stoughton.
