Perception

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Perception

• How do we define it?
• How we recognize and interpret stimuli
• Top down processing
• Remember, expectations and previous experiences
  play an influential role

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Selective Attention

• Our senses can take in approximately 11,000 bits
  of information at a time
• BUT
• We can only focus on one thing at a time

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Neissers Basketball Study

• Inattentional Blindness
• Focusing on one stimulus prevents us from
  noticing others
• The dancing gorilla (bear)
• Texting and driving!

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2 readers, one listener.

• Cocktail Party Effect
• Can listen to only one voice at a time
• Can notice gender
• Can detect name

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Just how much do we notice?

• Change blindness
• We fail to notice changes in our environment
  (when we are focusing on something else)

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Pop Outs!

• Striking distinctions grab our attention

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Perceptual Illusions

• Mislead us by playing on the way we organize and
  interpret our sensations
• (challenges our schema!)
• Reveal how we normally organize our sensations
  (thus clues to mechanisms of perception)
• Visual Capture Vision is our dominant sense
  (effects how we perceive our other senses)
• McGurk Effect (Youtube/edu)

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Perceptual Organization

• Visual Agnosia
• See all parts of an image, but not the whole, (or
  meaning)

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Gestalt (form)

• The whole is greater than the sum of its parts
• We tend to see, or group images as a whole, not
  as individual or isolated parts
• A natural, or innate form of perception

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Gestalt (How we group objects)

• Figure and ground (sometimes can be reversible)

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Gestalt

• Proximity

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Gestalt

• Similarity

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Gestalt

• Continuity

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Gestalt

• Closure

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Depth Perception

• Binocular Cues (interplay of two eyes)
• Retinal Disparity each eye sees object from
  slightly different angle (brain computes
  difference in vision to judge depth)
• Convergence eyes move together as item gets
  closer (brain detects convergence of eyes as
  measure of depth)
• The Finger Sausage!

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Depth Perception

• Monocular Cues
• Relative Size

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Monocular Cues

• Linear perspective

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Monocular Cues

• Texture gradient

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Monocular Cues

• Interposition

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Monocular Cues

• Relative Height

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Monocular Cues

• Relative Clarity

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Monocular Cues

• Relative Motion (The faster it moves)

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Monocular Cues

• Light and Shadow

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Motion Perception

• Phi Phenomenon
• Troxler Effect
• With loss of sight- motion is usually first to be
  restored

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Perceptual Constancy

• Perceiving an object as unchanging despite a
  change in stimulus
• Key factors Experience, Expectation (Rules of
  perception)
• Size Constancy
• As stimulus changes, we literally see changing
  size, but we know size has not changed due to
  experience and context of objects surroundings

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Size Constancyhttp//www.eruptingmind.com/depth
-perception-cues-other-forms-of-perception/
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Shape Constancy

• We know shape is constant even though our angle
  and thus vision of object changes

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Lightness (Color) Constancy

• We see objects as having consistent color, even
  as changing conditions alter the wavelength
  reflecting off the object.

http//www.psy.ritsumei.ac.jp/akitaoka/light5e.ht
ml
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Perceptual Set

• To believe it is to see it
• A mental predisposition
• Experiences give us a perceptual set, or
  assumptions that influence how or what we see

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Context Effect

• The context in which a stimulus appears affects
  how we perceive it
• eel is on the wagon.
• eel is on the orange.

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Sensory Deprivation / Restored Vision

• Adults with vision for first time (cataract
  surgery)
• Have Sense of colors, detect figure from ground
• No depth perception, no perceptual constancy
  (cortical cells not developed)
• Much of perception is learned during critical
  period in early development

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Perceptual Adaptation

• Our perception can adapt to change in stimuli,
  environment
• Inverted goggles!!

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Perceptual Constancypages 250-262

• Shape constancy
• Size constancy
• Light constancy

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• Sensory Deprivation and Restored Vision
• Perceptual Adaptation
• Perceptual Set
• Context Effects