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Gibson's Bottom Up Theory
Direct Perception involved Bottom-Up, or Data-Driven Processing. This is when
perception is primarily determined by the physical stimulus.
Gibson believed that the amount of data contained in the retinal image (the optic
array) contains a great deal of information about objects in the visual world, and
of those objects within it. This data is sufficient to explain perception.
Optic Flow Patterns: Produced when we move around the environment; thus
movement produces perceptual data. Gibson felt that movement (action) was a key
part of perception.
Invariants: Some aspects of the optic array remain the same when you move. These
aspects include: Horizon-Ratio Relation, and Texture Gradients. Invariant data is
collected automatically.
Affordance: Explains how the meaning of an object is perceived directly because its
use is obvious. The concept of affordance stems from the fact that there is a close
relationship between perception and action.…read more

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Gibson's Bottom Up Theory
(Research Evidence)
Gibson et al: Found that all the information that a pilot required was in the
optic array: a horizon line, a runway outline, ground texture, apparent
movement and so on, and that this provided sufficient information for
landing a plane.
Lee and Lishman: Built a "swaying room" so that they could manipulate
optic flow patterns. Children Typically fell over but adults were able to
adjust ­ showing that sensory and motor processes are linked, and that we
learn to adjust them.
Lee et al: Time-to-Contact is the idea that animals can judge distance and
speed of actions with respect to time using visual information only (direct).
This has been demonstrated by videotaping long jumpers. As they
approached take-off their stride length varied so that their final take-off
footfall position was correct.…read more

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Gregory's Top Down Theory
Constructivist theory is top-down or data driven processing.
Perception is primarily determined by best guesses based on
past experience.
Gregory described the process of perception as `hypothesis
testing' ­ a perceived object is a hypothesis, which is first
suggested, and then tested by sensory data. The stimulus
provided to our senses is often incomplete or ambiguous,
therefore Gregory believed that perception must rely on
cognitive expectations to help resolve ambiguities.…read more

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Gregory's Top-Down Processing
(Research Evidence)
The Effects of the Perceptual Set:
Motivation, Expectation, Emotion, and Culture all work to influence
perception.
Perceptual Constancy:
We perceive things such as size and shape as constant, despite a changing
retinal image. Size constancy can be demonstrated using the Ames Room.
Studies of Context:
Palmer: Showed participants contextual scenes (e.g. A Kitchen) and asked
them to identify objects. They correctly identified an object looking like a loaf
of bread 80% of the time. However, they were much less accurate when
identifying a drum, or a mailbox (40% Identification) presumably because their
perceptions were influenced by expectation about what was likely to be in a
kitchen.
Visual Illusions:
Are explained in terms of mistaken hypotheses. Gregory states that size
constancy rules for 3D objects are sometimes mistakenly applied to the
perception of 2D objects, although this can only fully explain some illusions.…read more

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Development of Perception
Gibson and Walk: Used the Visual Cliff to test depth perception in
infants aged 6-14 months. 92% refused to crawl over the cliff, even
if they wore a patch over one eye. This shows that; they perceived
depth, and that they were reliant on monocular cues only to do so.
It was deemed that this could have been due to other factors,
as by that age the infants had received plenty of sensorimotor
experience.
Campos et al: Observed younger infants by measuring their heart
rates when exposed to each condition. They found that their heart
rates were slower when on the shallow side.
Bower et al: Observed even younger infants and tested their
reactions to an approaching object. Infants were exposed to two
disks ­ one larger and further away, the other closer but smaller. The
infants were so upset by the smaller disk that the experiment was
abandoned early.…read more

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Comments

MrsMacLean

A very valuable presentation, thank you!

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