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THEORIES OF
PERCEPTUAL
ORGANISATION
Top-down and Bottom-up
 There are two theories of perception that
we will look at:
 Gibson’s Bottom-Up or Direct Theory
 Gregory’s Top-Down or...
GIBSON'S :BOTTOM UP
PROCESSING
THEORY
Gibson >> Gibbon >> Monkey >> Big Red
Bottom >> Bottom-Up Theory
What is bottom up
processing?
 Based on the assumption that we work
from bottom upwards in processing.
 For Gibson: sens...
What is bottom-up processing?
We start
with an
analysis of
sensory
inputs such
as patterns
of light.
This
information is
r...
 His theory of direct perception originated from
the work he carried out training pilots during
WW2.
 Important informat...
What is the optic array?
The patterns of light
reaching the eye can be
thought of as an optic
array containing all the
vis...
Optical Flow Patterns
 Changes in the flow of the optic
array contain important
information about what type of
movement i...
Texture gradient
 Our perceptual world is made up of textures
and these can be used to assist the perception
of depth and...
Affordances
How do we know what to do with an object?
Gibson suggests that the uses of objects are perceived
directly – th...
Affordances – an example
‘... I was lazily sitting in a chair reading a book in the sun.
Suddenly my attention was drawn t...
Evaluation of Gibson’s theory
 What’s good or bad about it?
 Read the evaluation points in your booklet and
identify whi...
Gregory’s Theory – also known as Constructivist,
Indirect or Top-down
Gibson’s Theory – also known as Direct or
Bottom-up
...
Essay Time
In groups, plan the following essay title:
“Describe and evaluate Gibson’s bottom-up
(direct) theory of percept...
GREGORY’S TOP DOWN
THEORY OF PERCEPTION
Stimulus information from our
environment is frequently ambiguous so to
interpret ...
Top down processing
 You dnot need all the ltetres of
wrdos to be in the croerct odrer to
raed a snetncee.
A lot of environmental information reaches the eye, but
much is lost by the time it reaches the brain (Gregory
estimates a...
.
.
• Gregory proposed that often when we construct our
perception of reality it involves making more than
one hypothesis ab...
Perceptual Set
 Perceptual set is a top-down activity identified
by Allport in 1955.
 “This is the perceptual bias or pr...
 Several factors can influence perceptual set
including:
 Context/expectation
 Emotion
 Motivation
 Culture
Activity
In groups find one study that shows the
influence of perceptual set for the factor you
have been allocated from t...
Recap
Gregory's Theory
Q1. Gregory's theory is known as what kind
of theory?
A: Indirect or Top-down theory
Q2. Gregory's theory is also known as the
constructivist theory.
True or False?
A: True
Q3. How much information is lost between
our eyes and our brains?
A: About 90%
Q4. We use past experience and
knowledge to help fill in the gaps when
perceptual information is ambiguous.
True or False?...
Q5. Gregory believes the information that
comes from the environment and into our
perceptual system is not important for
p...
Q6. What concept developed by Allport can
be used to support Gregory's theory?
A: Perceptual set
Q7. Perceptual set is the idea that our
perception is influenced by the
expectations that we bring to the
situation.
True ...
Q8. Briefly describe Palmer's study which
supported Gregory's theory.
A: Toaster, mail box and drum placed in a
kitchen se...
Q9. How can Gregory explain illusions?
A: When an image is ambiguous, eg:
perhaps has two interpretations, we use
past exp...
Evaluation of Gregory’s
theory
There is considerable evidence to support the idea that we
often make use of stored informa...
Activity
Comment Explanation of the comment in relation to
Gregory’s theory
Perception occurs
quickly and normally
accurat...
Conclusion
 It seems likely that the process of perception
uses a combination of information from
sensory input (direct t...
Gregory’s Theory – also known as Constructivist,
Indirect or Top-down
Gibson’s Theory – also known as Direct or
Bottom-up
...
There are various examples of illusions that can
be applied to Gregory’s hypothesis testing
theory. One is the Rat-man, be...
Now it’s your turn……
 You are now going to carry out an experiment
to test Gregory’s theory of hypothesis testing.
 We w...
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  1. 1. THEORIES OF PERCEPTUAL ORGANISATION Top-down and Bottom-up
  2. 2.  There are two theories of perception that we will look at:  Gibson’s Bottom-Up or Direct Theory  Gregory’s Top-Down or Indirect Theory
  3. 3. GIBSON'S :BOTTOM UP PROCESSING THEORY Gibson >> Gibbon >> Monkey >> Big Red Bottom >> Bottom-Up Theory
  4. 4. What is bottom up processing?  Based on the assumption that we work from bottom upwards in processing.  For Gibson: sensation is perception: what you see if what you get  It assumes that there is enough information provided in the sensory input to allow the individual to make sense of the world around, without experience.
  5. 5. What is bottom-up processing? We start with an analysis of sensory inputs such as patterns of light. This information is relayed to the retina where the process of transduction into electrical impulses begins These impulses are passed into the brain where they trigger further responses along the visual pathways until they arrive at the visual cortex for final processing.
  6. 6.  His theory of direct perception originated from the work he carried out training pilots during WW2.  Important information is provided by the movement of the observer.  From his work, he developed three main components:  Optic flow patterns  Role of invariance  Affordances
  7. 7. What is the optic array? The patterns of light reaching the eye can be thought of as an optic array containing all the visual information available at the retina. This optic array provides unambiguous information about the layout of objects in space. Light rays reflect off of surfaces and converge into the cornea of your eye. If you move, the structure of the optic array changes.
  8. 8. Optical Flow Patterns  Changes in the flow of the optic array contain important information about what type of movement is taking place. For example:  i ) Any flow in the optic array means that the perceiver is moving, if there is no flow the perceiver is static.  ii) If a flow seems to be coming out from a particular point, this means the perceiver is moving towards that point; but if the flow seems to be moving towards that point, then the perceiver is moving away.  Maher & West (1993) – black clad The Optic Flow pattern for a person looking out of the back of a train
  9. 9. Texture gradient  Our perceptual world is made up of textures and these can be used to assist the perception of depth and orientation.
  10. 10. Affordances How do we know what to do with an object? Gibson suggests that the uses of objects are perceived directly – that is they offer (afford) a certain response, eg: a chair affords sitting but the affordance can change with the circumstances so if we need to reach something, it affords standing on. A rock could be a seat or a statue in a garden. He believed that the affordances could vary between species eg: the affordance of a washing line to a bird and a human.
  11. 11. Affordances – an example ‘... I was lazily sitting in a chair reading a book in the sun. Suddenly my attention was drawn to movement to one side. I looked down and to my horror saw a large snake advancing towards me. My first instinct was to frighten it away by throwing something on it and I looked around for a suitable object. Bending down, I picked up some gravel and threw it at the snake. According to Gibson, the graspability, and throwability, of gravel was directly perceivable to me. I was able to perceive which items in my immediate environment were capable of being grasped and thrown without having to consult any previous experience. I didn’t attempt to pick up and throw the
  12. 12. Evaluation of Gibson’s theory  What’s good or bad about it?  Read the evaluation points in your booklet and identify which are strengths and which are weaknesses.
  13. 13. Gregory’s Theory – also known as Constructivist, Indirect or Top-down Gibson’s Theory – also known as Direct or Bottom-up Definition Supporting evidence Challenging evidence Summary of Theories of Perceptual Organisation
  14. 14. Essay Time In groups, plan the following essay title: “Describe and evaluate Gibson’s bottom-up (direct) theory of perception. (8 marks + 16 marks)”
  15. 15. GREGORY’S TOP DOWN THEORY OF PERCEPTION Stimulus information from our environment is frequently ambiguous so to interpret it, we require higher cognitive information either from past experiences or stored knowledge in order to draw conclusions and perceive. Helmholtz called it the ‘likelihood principle’.
  16. 16. Top down processing  You dnot need all the ltetres of wrdos to be in the croerct odrer to raed a snetncee.
  17. 17. A lot of environmental information reaches the eye, but much is lost by the time it reaches the brain (Gregory estimates about 90% is lost). Therefore, the brain has to guess what a person sees based on past experiences using higher cognitive input. In this way we are actively constructing our perception of reality based on our environment and stored information.- Sensory stimuli from environment Higher cognitive input from past experiences and stored information Perception
  18. 18. .
  19. 19. . • Gregory proposed that often when we construct our perception of reality it involves making more than one hypothesis about what we actually perceive. • If we form a correct hypothesis we will perceive correctly, however if we form an incorrect hypothesis it will lead to errors in our perception and this explains why we are sometimes tricked by optical illusions. • Our brain has formed an incorrect hypothesis or two equally plausible hypotheses and is jumping between the two in our actual perception.
  20. 20. Perceptual Set  Perceptual set is a top-down activity identified by Allport in 1955.  “This is the perceptual bias or predisposition or readiness to perceive particular features of a stimulus” (Allport, 1955)
  21. 21.  Several factors can influence perceptual set including:  Context/expectation  Emotion  Motivation  Culture
  22. 22. Activity In groups find one study that shows the influence of perceptual set for the factor you have been allocated from the list in your booklets. Summarize the study in no more than 100 words. Include some evaluation points as well as a description. This will then be shared with the rest of the class.
  23. 23. Recap Gregory's Theory
  24. 24. Q1. Gregory's theory is known as what kind of theory? A: Indirect or Top-down theory
  25. 25. Q2. Gregory's theory is also known as the constructivist theory. True or False? A: True
  26. 26. Q3. How much information is lost between our eyes and our brains? A: About 90%
  27. 27. Q4. We use past experience and knowledge to help fill in the gaps when perceptual information is ambiguous. True or False? A: True
  28. 28. Q5. Gregory believes the information that comes from the environment and into our perceptual system is not important for perception. True or False? A: False
  29. 29. Q6. What concept developed by Allport can be used to support Gregory's theory? A: Perceptual set
  30. 30. Q7. Perceptual set is the idea that our perception is influenced by the expectations that we bring to the situation. True or False? A: True
  31. 31. Q8. Briefly describe Palmer's study which supported Gregory's theory. A: Toaster, mail box and drum placed in a kitchen setting. Ppts mistook the mailbox but not the drum for a toaster. The expectation of seeing a toaster in a kitchen influenced our perception when the image was ambiguous (when it was the mailbox).
  32. 32. Q9. How can Gregory explain illusions? A: When an image is ambiguous, eg: perhaps has two interpretations, we use past experience and knowledge to decide what we are looking at. Eg:
  33. 33. Evaluation of Gregory’s theory There is considerable evidence to support the idea that we often make use of stored information and past experience to guide our perceptual processes. Gregory’s theory can explain why individuals perceive the same stimulus differently (because of different schemas/past experience)
  34. 34. Activity Comment Explanation of the comment in relation to Gregory’s theory Perception occurs quickly and normally accurately Most of the research has been carried out in artificial surroundings and involves the use of ambiguous stimuli shown for short periods of time (lab Further Evaluation
  35. 35. Conclusion  It seems likely that the process of perception uses a combination of information from sensory input (direct theory) and from our past experiences and knowledge (indirect theory). The first part may be bottom-up, but the top- down process begins an instant later. (Matlin, 2005)  Eysenck suggested that there are two perceptual systems: vision for action which doesn’t rely on previous knowledge (support for Gibson) and vision for perception which requires the use of previous knowledge (support for Gregory).
  36. 36. Gregory’s Theory – also known as Constructivist, Indirect or Top-down Gibson’s Theory – also known as Direct or Bottom-up Definition Supporting evidence Challenging evidence Summary of Theories of Perceptual Organisation
  37. 37. There are various examples of illusions that can be applied to Gregory’s hypothesis testing theory. One is the Rat-man, because no context is provided we assume it is both a rat and a man, our brain switches between both images. Another popular illusion is the young and old woman that can be applied similarly to Gregory’s hypothesis testing theory.
  38. 38. Now it’s your turn……  You are now going to carry out an experiment to test Gregory’s theory of hypothesis testing.  We will use this later on in the course when looking at research methods.

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