Perception: Gregory's Top-Down Processing Theory of Perception Flashcards
What type of theory did Gregory come up with?
A top-down indirect theory of perception
What is Gregory’s Theory?
Gregory believed that we construct our own perceptions by combining the perceptual information received by the eye (direct data) with stored knowledge in the brain. Therefore, perception is indirect because it relies on the addition of this stored knowledge.
Name the 3 things Gregory’s Theory is based on
> Sensory Data
Knowledge stored in the brain
A Hypothesis of what is out there
Describe Perception as hypothesis formation
What we ‘see’ is not a direct consequence of the stimulus input, but the end product of an interaction between the original stimulus, internal expectation and hypotheses. This process is necessary, because the brain must make inferences about the external environment based on frequently inadequate information supplied by the senses.
Describe the role of previous knowledge and expectation
The key element in this process of indirect perception is the knowledge stored from past experience, which produces expectations and hypotheses, and which in turn affects perception. A Study by Bruner et al showed false playing cards to participants (e.g. red clubs or black hearts). The participants expected black clubs or red hearts, so their perceptual systems coped by ‘seeing’ cards that were purple or brown, showing that expectations distorted their perceptions.
Discuss visual illusions
According to Gregory’s Theory, the formation of incorrect hypotheses or expectations leads to errors of perception, such as visual illusions.
Gregory suggests that many visual illusions are the result off ‘misapplied hypotheses’, hypotheses that normally work in the ‘real’ world but have been misapplied. For example, converging lines are usually correct in informing us about which objects are closer or further away. These cues are used by artists when producing two-dimensional drawings of the three dimensional world.
Discuss Support of Hypothesis testing in perception
Once a hypothesis has been formed it may be tested against reality; in fact that is how infants develop their perceptual abilities.
Name research to support Hypothesis testing in perception
Khorosani et al. found that the Muller-Lyer had less effect once participants knew about the illusion.
Discuss research evidence which supports Visual Illusions in perception
Visual illusions show that tricks of perception can be explained in terms of misapplied hypotheses based on usual relationships between objects.
Name research which supports visual illusions in perception
Segall et al.
Discuss Segall et al.’s findings
Segall et al. found that people who do not live in ‘carpentered’ environments are less likely to percieve differences in the length of the two lines in the Muller-Lyer illusion. They would not be used to seeing the edges of buildings or the corners of rooms
Describe a strength of Gregory’s Theory
The indirect approach can explain the way our perceptual system deals with ambiguous situations where the retinal is poor. Prior experience provides possible solutions.
Describe a weakness of Gregory’s Theory
Indirect theory is criticised because it is largely based on the study of perception in artificial settings and therefore fails to explain much of our real-world perception.
AID: Real World Application
Our understanding of the effect of expectations is important in questioning what we think we are seeing. In 1988 a US naval Ship launched a guided missile which shot down an Iranian plane killing 260 people. A military investigation blamed the radar operators aboard the ship who had mistakenly convinced themselves that the plane they saw in their radar was an enemy. Once they had formed the perception, they interpreted the plane’s flight as a direct threat to the Naval ship and were convinced it meant to attack it.
