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Illusions Are A Good Thing. Thesis Illusions are good because: – They tell us about perceptual strategies used by the brain – These perceptual strategies.

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Presentation on theme: "Illusions Are A Good Thing. Thesis Illusions are good because: – They tell us about perceptual strategies used by the brain – These perceptual strategies."— Presentation transcript:

1 Illusions Are A Good Thing

2 Thesis Illusions are good because: – They tell us about perceptual strategies used by the brain – These perceptual strategies work most of the time; without them, our perception would be much worse

3 About Illusions Illusions occur when our perceptions are not consistent with the environment Illusions are rare Illusions are difficult to override

4 Example 1: Phantom WordsPhantom Words Problems for speech perception – Segmenting the speech signal – Variability in the speech signal What does the phantom words illusion reveal? – Top-down processing

5 Example 2: The Moon Illusion Problems for depth perception: – The retinal image is two dimensional – Size of the retinal image depends on both distance of the object and size of the object

6 What Does the Moon Illusion Reveal about the Brain? Contextual cues can affect perception of distance Unconscious inference: the brain makes perceptual calculations, such as apparent distance, quickly and without conscious awareness

7 Example 3: Negative Color Afterimage Problems for color perception: – Why do there seem to be “primary” colors? – Why can you say “bluish green” but not “reddish green?”

8 What do Negative Color Afterimages Reveal? Importance of neural adaptation Opponent pairs of colors: – Red-green – Blue-yellow – White-black

9 What if We Didn’t Have Illusions? How would we understand speech? How would we perceive distance and size? How would we discriminate between different colors?


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