Psya3 Perception

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Gregory's Indirect Theory of Perception
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Top-down or Constructivist

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Gregory’s theory is more ‘constructivist’ or ‘top-down’ than Gibson’s. Gregory believes that perception occurs ONLY after incoming data from our senses has been understood in relation to information that is already stored in the brain. So although Gregory credits the importance of incoming information from our senses (as did Gibson), he disagrees with Gibson’s key idea that perception can occur without intervention from higher cognitive processes. Gregory believed that sensory input alone is insufficient; what we see is stimulus input and also an internal expectation and formation of hypotheses.

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Gregory's Indirect Theory of Perception
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Hypothesis Testing

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According to Gregory, we formulate hypotheses to test the knowledge we are receiving from our senses. The Necker Cube is an example of the ‘hypothesis testing’ proposed by Gregory. It gives us two potential realities; one where the dot is at the front of the cube or one where the dot is at the rear corner of the cube.

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Gregory's Indirect Theory of Perception
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Expectations and Perceptual Set

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Expectations, or perceptual set, is a key component of Gregory's Theory. This is where we are prepared for what we are to see from the context or previously stored information. Individuals are possibly biased in how they perceive due to their previous experiences, cultural factors, and emotional and motivational influences. Bruner and Minturn's classic (1955) research showed how the character ‘I3’ could be perceived as a ‘B’ or '13' depending on whethe it was displayed with letters or numbers.

For most of the time, expectations are quite useful, it may 'speed up' perception but on the other hand people may see what they want or expect to see increasing the opportunities for errors to occur.

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Gregory's Indirect Theory of Perception
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Importance of Illusions

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Gregory believes that visual illusions are experienced because expectations based on past experiences are used to create and test hypotheses from incoming sensory information – but sometimes errors happen and false perceptions are experienced. In the case of illusions, hypotheses that we may be testing are misapplied. In the real world converging lines usually indicate depth, but they are frequently used in 2-D art to represent the 3-D world.

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Gregory's Indirect Theory of Perception
AO2 Criticism 1
Can only Gregory's Theory explain perception?

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It is claimed that direct theories of perception are insufficient in explaining illusions and therefore constructivist theories must be correct. However, most illusions, like the Ames room, can be understood if the observer is allowed to 'move around' the illusion, so direct theories of perception, like Gibson, are also able to explain illusions if they exist in a 3D world.

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Gregory's Indirect Theory of Perception
AO2 Criticism 2
Is the supporting research valid?

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Gregory’s constructivist theory can be criticised due to its supporting research being highly artificial. For example, Palmer's (1975) research, for example, involves ambiguous and fragmented information. In this situation it would be very difficult to rely on bottom-up processing and the effects of context and experience are magnified because of the dubious nature of the stimulus material. The artificiality of this research jars with the ecological approach used by Gibson.

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Gregory's Indirect Theory of Perception
AO2 Criticism 3
Do illusions exist in the real world?

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One limitation of this explanation of perception is that visual illusion research offers the main support for Gregory’s theory. Although research shows that these 'tricks of perception' can be explained in terms of misapplied hypotheses, there are actually very few 'naturally occurring' illusions. So is it logical to accept Gregory’s theory which is based on illusions to explain how perception works in the real world?

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Gregory's Indirect Theory of Perception
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Real world applications of Perceptual Set

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'Perceptual Set', an aspect of Gregory's theory, can however be used to explain behaviour in the real world. The incident with the USS Vincennes, where US sailors shot at an Iranian passenger plane because they had become convinced (set) that the plane was an enemy intent on attacking them. Having an understanding of this concept is useful when asking individuals to question what they think they are seeing.

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Gregory's Indirect Theory of Perception
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Can account for cultural variations.

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Gregory's theory is not culturally biased, in fact it can account for why there seems to be cultural variations in perception. Segall (1963), for example, reported that Zulu participants were less susceptible to the Muller-Lyer illusion. Gregory claims the differences are the product of the different cultures appreciation of their very different living environments, such as the Zulus living in a round rather than carpentered world.

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Gregory's Indirect Theory of Perception
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Nature vs Nurture

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Gregory's theory really supports the Nurture side of this debate, as it believes that sensory input alone is fragmentary and ambiguous. We must therefore rely on stored knowledge and expectation, both of which rely on our experiences. The fact there are cultural differences in perception supports both Gibson's indirect theory and a more 'nurture' view of perception overall.