Richard Gregory Suggests That Perception is a Process of “Hypothesis Testing” Essay Example
Roth (1986) defines perception as "the means by which information is acquired through the sense organs and transformed into experiences of objects, events, sounds and taste. " The constructivist psychologist, Richard Gregory (1998) describes such perceptions to be "like the predictive hypotheses of science". His theory of "hypothesis testing" suggests that data from the retinal image interacts with previous appropriate knowledge, creating 'psychological data', whereby the hypotheses try and make sense of it all.
Visual illusions occur when hypotheses are applied to the illusionary medium in the same way they would visually be applied to real life settings. However, because of the 'unnatural' organisation of cues in the illusionary medium, the hypothesis that is formed is inappropriate which results in an illusion. I would move this para down. An example of such an illusion
...is provided by Goldstein (1999). When a person hypothesizes that a shadowy object in a dark corner across the room is a table, however, closer inspection reveals that this hypothesis is incorrect as the table is actually a toy drum.
Goldstein (1999) this process is conscious, as one is aware of the hypotheses that eventually lead to the perception of the drum. However, not all hypothesis testing occurs at a conscious level. Ki?? lpe (1904) puts forward the idea of 'mental operations' occurring during perceptual processes. He presented displays of different colours and told participants to concentrate on a certain dimension of the display, like the positioning of the letters. When Ki?? lpe asked his participants to describe a different aspect of the display, like the colour of a certain letter, they could not.
Ki?? lpe concludes that despite all of the information fro
the presented display reaching the participants eye, a careful selection process comes about between the 'reception' of this information and the participant's perception, resulting in only some of the information being perceived and remembered. (Cited in Goldstein 1999). This implies that it is the observer that contributes to such a process rather than perception depending wholly on the properties of the stimulus.
Gregory's hypothesis theory can also be explained by an experiment carried out by Palmer (1975). He presented a pictorial scene to participants (e. g. a kitchen scene), followed by a brief presentation of a picture of an object. It was found that the probability of identifying an object correctly was highest when the object was relevant to the context (e. g. a loaf), intermediate when no context was given (i. e. no picture was shown before the object picture) and lowest when the object was irrelevant to the picture (e. g. a drum). (Cited in Eysenck & Keane 2000).
Such findings cannot be explained by any direct processing theories, which are usually driven by bottom-up processing but only by indirect constructivist theories like that of Gregory's hypothesis testing (1973). The constructivist approach to perception is concerned with how perceptions are constructed by the mind. Any approach to perception that is concerned with perceptual processing is included within the constructivist approach (Goldstein 1999). Constructivist processing theories are mainly dependent on internal processes and driven by both top-down and bottom-up processes.
It was Hermann Von Helmholtz (1821 - 1894) who formed the early roots of the constructivist approach. He thought of visual perceptions as 'unconscious inferences' which add meaning to sensory information and believed these inferences to be
conscious as one is not commonly aware that inferences are being made while perceiving (cited in Eysenck ; Keane 2000). Helmholtz proposed the 'likelihood principle', which assumes that a person perceives an object that is likely to be the cause of sensory stimulation. Goldstein (1999) explains this principle.
If a number of 'objects could have caused a particular pattern of light and dark on the retina', the object that is most likely to occur in that particular situation will be perceived. It is Gregory's hypothesis testing that follows on from the likelihood principle. Gregory (1973) and other constructivist theorists like Bruner (1957) and Neisser (1967) all believe in the assumptions, which Helmholtz had proposed previously: that perceptions are influenced by hypotheses and expectations which are at times incorrect. This therefore implies that perception is 'prone to error' (cited in Eysenck & Keane 2000).
Ames (1949) conducted an experiment where participants viewed two illuminated balloons in a dark room. Ames inflated one of the balloons during the experiment which the participants where unaware of. A large majority of participants reported that the balloon had moved closer rather than grown larger. Such an experiment supports the evidence behind cue theory, which Gregory's (1973) work on 'misapplied size constancy' theory is extended from. Ittelson (1952) argued if a visual display appears familiar but is actually unfamiliar, the perceptual hypotheses formed could be inaccurate.
The Ames distorted room is a good example of this. The room is an unusual shape, however when it is viewed from a certain angle, it actually looks like a normal rectangular room. In reality, one corner of the room is actually further away from the observer than
the other corner and so when a person walks backwards and forwards along the back wall, they appear to grow and shrink. However, according to constructivists, if the person in the distorted room happens to be a close relative of the observer, then there is a greater chance that the room would be seen as having an odd shape.
Motivational and emotional states may also influence perceptual hypotheses, and in turn, visual perception. One of the main assumptions of the constructivist approach is that it is dependant on internal processes. A study by Bruner and Goodman (1947) illustrated this. They studied motivational factors by asking rich and poor children to estimate the sizes of coins. They found that poor children overestimated the sizes of coins as apposed to rich children. The major bias here however is that poor children may have overestimated the size of the coins because of the importance of money to them as apposed to rich children.
However, rich children may have been more familiar with coins and so estimated their sizes more accurately. A modified version of this experiment was conducted by Ashley et al. (1951). They hypnotized participants into believing they were either poor or rich and found that the 'poor' condition overestimated the size of the coins as apposed to the rich condition. This is a strength of the constructivist approach as it can account for the role of motivation and emotion in perception since it strongly acknowledges the importance of internal states in determining perception (cited in Eysenck ; Keane 2000).
Similar to Gregory's hypothesis theory is schema theory. This assumes that a cue calls upon a mental schema, rather than
a hypothesis, which Gregory suggests. Anderson (1980) defines schemas as "large complex units of knowledge that encode properties that are typical of instances of general categories and omit properties which are not typical of the categories". An important function of schemas is to allow a person to gather relevant information from where it is needed but absent.
The idea is similar to Gregory's hypothesis theory, however this provides a richer account of the information that is called up by the cue. As already mentioned, Gregory's (1973) constructivism based hypothesis theory accounts for a number of visual illusions where the 'unnatural' use of cues leads for the misapplications of hypotheses (e. g. Ames 'distorted room' described above). Secondly, Palmer's (1975) study outlined above can only be accounted for in terms of hypothesis theory (and schema theory) and cannot be explained in terms of any bottom-up based theory.
However, not all theorists agree with the constructivist approach. The approach seems to predict that perceptions will often be inaccurate while it is known that they are extremely accurate in almost all naturalistic situations. The environment surely consists of more information than "fragmentary scraps" assumed by constructivist theorists (Eysenck ; Keane 2000). Also most of the evidence used in support of the constructivist approach is based on artificial stimuli that do not occur naturally in the real world.
Studies such as that of Bruner et al. (1951) and Palmer (1975) presented visual stimuli only briefly, reducing the likelihood of using bottom up processing and giving chance for hypotheses (top-down processes) to be used (cited in Eysenck ; Keane 2000). Lastly, constructivists such as Gregory have not fully explained the visual illusions. Such
illusions depend on a variety of factors and so general theories such as 'misapplied size constancy' theory for illusions like the Muller-Lyer, may not be as influential.
