PS2822 week 4 Visual perception

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Principle of visual perception : Seven steps
1. Environmental stimulus
2. light is reflected and transfered
3. receptor processes
4. Neural processing
5. perception
6.Recognition
7. Action
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Neural processing
This involves interactions between the signals travelling in the networks of neurons in the retina (bipolar, horizontal, amacrine and ganglion cells, and later on the pathway to the brain.)
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Computational approach : computer vision systems
Mathematical analysis of the luminance structure in 2-D images provides information about the structure of surface of objects in 3-D space.
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Comparison man-machine
Computer vision can discriminate cats from dogs with 90% accuracy
Identify different breeds of cats and dogs with about 60% accuracy
Can determine, as well as humans, whether two faces in frontal views are the same or not, but make more mistakes when face
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Helmholtz’s theory of unconscious inference
we perceive the object that is most likely to have caused the proximal stimulus.

Our perceptions are the result of unconscious inferences, that we make about the environment.

This inference happens rapidly and unconsciously.

Solving problem approach in
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Regularities in the environment
Physical regularities : regularly occurring physical properties of the environment.

Semantic regularities: characteristics associated with the functions carried out in different types of scenes. The meaning of a given scene is related to what is happenin
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The Bayesian inference
The estimation of the probability of a given outcome is influenced by two factors:
The prior probability (our initial belief about the probability of an outcome)
The likelihood of a given outcome
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Experience dependent plasticity
Theory of natural selection : characteristics that enhance survival chances are passed to the next generation. Then the visual system may have been shaped to contain neurons that respond to features that are frequent in the natural environment.

Neurons a
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Pragnanz principle = Figural Goodness
Aspect of the perceptual experience that is a composition of simplicity, order and regularity of an object.
Many different perceptions are possible for any given figure and that ‘figural goodness’ determines which one is actually perceived.
There are ev
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Perceptual Grouping
Law of proximity - Close objects tend to be grouped together.

Law of continuity - Organizing images to produce smooth continuities rather than abrupt changes.

Law of Similarity - Similar objects tend to be grouped together.

Law of closure - The whole s
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New principles of perceptual grouping
Synchrony : visual events that occur at the same time tend to be perceived together
Common region
Element connectedness
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Color Constancy
Perception of colors is relatively constant in spite of changing light sources.
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Mechanisms of colour constancy
Chromatic adaptation occurs when exposed to chromatic color leads to receptors:
“Adapting” when the stimulus color selectively bleaches a specific cone pigment
Decreasing in sensitivity to the color

White balance : adaptation occurs to light sources lea
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Other cards in this set

Card 2

Front

Neural processing

Back

This involves interactions between the signals travelling in the networks of neurons in the retina (bipolar, horizontal, amacrine and ganglion cells, and later on the pathway to the brain.)

Card 3

Front

Computational approach : computer vision systems

Back

Preview of the front of card 3

Card 4

Front

Comparison man-machine

Back

Preview of the front of card 4

Card 5

Front

Helmholtz’s theory of unconscious inference

Back

Preview of the front of card 5
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