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Aristotle documented the first visual illusion

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Parva Naturalia (384-322 A.C.)

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___________________________________ Is everything an illusion?

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What is an illusion? Subjective perception does not match the real world Examples: See something that is not there

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Fail to see something that is there See something different from what is there Illusions are critical to understanding how our brains construct visual experience

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Neural limitations lead to neural deceptions Filling-in blanks Seeking structure Improving narratives

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Neural limitations lead to neural deceptions Filling-in blanks Seeking structure Improving narratives

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Neural limitations lead to neural deceptions Filling-in blanks Seeking structure Improving narratives

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Choice Blindness Johansson, Hall, Sikström & Olsson (2005)

Which of the two faces is more attractive?

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Subjects’ comments

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Illusions dissociate perception from reality  Illusions reflect what the brain is actually doing  All that we perceive is an illusion in part or whole

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 Scientists study illusions to understand the brain  Artists use their intuitions about the mind to create

illusions

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Illusions in magic Special effects

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Secret devices and mechanical artifacts (gimmicks) Optical illusions Misdirection of attention Visual illusions

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Memory Illusions Cognitive illusions Illusory correlations

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Choice illusions

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Misdirection  The diversion of the spectator’s attention away from the

‘method’ (the secret behind the ‘effect’) and towards the effect (what the spectator perceives)

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 Overt misdirection: the magician redirects the spectator’s gaze away from the method.

 Covert misdirection: the magician draws the spectator’s attention away from the method without redirecting the spectator’s gaze.  Covert misdirection is exemplified in cognitive science by the paradigms of change blindness and inattentional blindness.

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Change blindness

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Whodunnit?

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Inattentional Blindness

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The attentional spotlight

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Martinez-Conde & Macknik, Scientific American 2007

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The attentional spotlight

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Tse (2005). Vision Research

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Attention dynamically enhances and suppresses our perception

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Chen, Martinez-Conde, Macknik, Bereshpolova, Swadlow & Alonso (2008). Nature Neuroscience

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