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30 Cards in this Set
- Front
- Back
Problems faced by the visual system |
The image of the retina is ambiguous. Inverse Projection Problem. Many objects in the environment are hidden from view. Objects look different from different viewpoints. View point invariance. |
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Inverse projection problem |
An image on the retina can be caused by an infinite number of objects. Use multiple viewpoints. Use previous experience. |
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Gestalt laws of perceptual organization |
Perceptual organization is grouping of elements together to create a larger object. Law of simplicity, law of similarity, Good continuation, proximity, common region, uniform connectedness, synchrony, Common fate. |
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Law of simplicity |
every stimulus is seen in a way that the structure is as simple as possible. |
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Law of similarity |
Similar things appear to be grouped together. |
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Good continuation |
Points that appear to make a smoothly curving line when connected will be grouped together. |
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Proximity |
things that are near one another will be grouped together. |
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Common region |
Elements in the same region of space will be grouped together. |
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Uniform connectedness |
A connected region of visual properties is perceived as a single unit. |
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Synchrony |
Visual events that occur at the same time are seen as belonging together. |
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Common fate |
Objects moving in the same direction are grouped together. |
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Meaningfulness or familiarity |
Things that form patterns that are familiar or meaningful will be grouped together. |
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Distinguishing figure from ground |
Figure ground segregation. Figure seems to be more object like. Figure seems to be in front of the background. The contours bordering the figure and ground appear to belong to the figure (border ownership). |
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Recognition by components |
Recognition by components theory explains how basic units of objects can be combined to make larger objects. |
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Geons |
A perceptual alphabet (approx 36) to construct objects |
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Non accidental properties |
Properties of edges in the retinal image that correspond to edges in the 3D environment. Each geon has a unique set of non accidental properties. Non accidental properties allow for viewpoint invariance. |
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Principle of componential recovery |
If we can recognize the individual geons we can recognize the object. Allows us to recognize occluded objects. Deleting contours from objects that specify the relation between geons impairs recognition. |
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Scene perception |
We are able to extract information from scenes extremely rapidly (less than 250ms) |
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How can we perceive the gist of a scene so rapidly? |
Global image features that are rapidly perceived. Degree of naturalness, degree of openness, degree of roughness, degree of expansion, colour. |
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Physical regularities |
Regularly occurring physical properties in the environment |
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Semantic regularities |
Previous experience, knowledge and expectations also allow us to process scenes quickly. Allow us to make rapid inferences about scenes. Likelihood principle - we perceive the object that is most likely to have caused the pattern of stimulation received. |
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Physiology of object and scene perception |
Neural responses to grouping in V1. Good continuation and similarity. |
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Neural responses to figure ground |
Response in V1 was modulated by whether the stimulus in the receptive field was seen as 'figure' or 'ground'. Stimulus on the retinal remains constant but the neuron changes its response. |
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Neural coding of objects |
Distributed coding- when a particular object is represented by the firing of a group of neurons. Sparse coding - coding of objects by only a few neurons. Distributed coding within a brain region and between brain regions. |
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EBA |
responds to bodies |
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FFA |
responds to faces |
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LOC |
responds to objects |
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PPA |
responds to places |
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Binocular rivalry |
A different image is presented to each eye simultaneously. the subject can only be aware of one image at a time. |
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Mind reading with fMRI |
Created a statistical model that was able to correlate patterns of activation in V1 with different orientations. The model was accurate at determining which orientation was presented in a different group of subjects. |