Perception

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Perception

• Psychology 1106

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Introduction

• When we talked about sensation we were concerned
  with moving from one for of energy or another to
  neural energy
• Bottom up processing
• Perception is top down
• Imposing organization on sensation

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Attention

• Basically the allocation of perceptual resources
  to sensation
• Selective attention means that we can only focus
  these resources in a limited way
• The Cocktail Party Effect
• Lots of stuff going on, you hear lots of stuff,
  but only listen to the conversation you are in
• Tested with dichotic listening

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Dichotic Listening

• Different messages in each ear
• Shadow one ear
• Cant even tell the language spoken in the
  unattended ear!
• If story moves from one ear to another, you
  cannot help but follow it
• Same with vision! (Becklen and Cervane, 1985)

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Dichotic stuff

• Even if not perceived, stimuli can affect
  behaviour
• Wilson (1979)
• Preferred previously herd tunes!
• Could NOT identify them
• Szostalo (1998)
• Learned contingency they could not identify

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Form Perception

• How do we tell the difference between an object
  and the background
• Gestalt psychologists thought we use various
  rules
• Proximity -gt group nearby things together
• Similarity -gt similar figures are grouped
  together
• Continuity -gt smooth continuous patterns
• Closure -gt we fill in gaps
• Connectedness -gt perceive spots, lines, areas as
  a single unit when connected

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Examples

• Proximity
• Closure
• Continuity

• Similarity
• connectedness

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Depth Perception

• A two dimensional image is projected on your
  retina
• Yet, you see in 3 D
• Whats up with that?
• Somewhat built in
• Visual cliff experiments (Gibson and Walk, 1960

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Binocular cues

• Your eyes receive subtly different information
  because they are in different locations
• This retinal disparity provides a cue as to how
  far awy an object is
• This is how 3D movies work
• Convergence too, how far in your eyes are turned,
  the angle

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Monocular Cues

• Many other cues rely only on one eye
• Relative size
• Bigger is closer

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Monocular Cues

• Interposition
• Something blocking something else is closer
• Relative clarity
• Clearer is closer

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More Monocular Cues

• Texture gradient
• More detail closer
• Relative height
• High far, unless there is an horizon

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More Monocular Depth Cues

• Motion parallax
• Faster moving stuff is closer
• Relative brightness
• Brighter is closer

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• So, even though I have no true three-dimensional
  vision, I can see in D
• Solely based on monocular cues

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Motion perception

• Looming effect
• Things seem to be coming at you when they get
  bigger
• Things seem to be going away from you when they
  get smaller
• Even in babies
• A rapid series of slightly different images
  conveys movement
• Oddly enough bobbing your head doesnt convey
  motion

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Motion perception

• The phi phenomenon illusion does a nice job of
  illustrating how motion perception works

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Perceptual Constancy

• A book is perceived as a book, even when the
  retinal image is radically different
• The proximal stimulus is, in fact very different

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Size Distance relationships

• Small is far away
• Probably explains some illusions
• Importance of edges
• Experience plays a role

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Lightness Constancy

• Black paper reflects 100 times more light than
  white paper, if the black paper is in sunlight
  and the white is in your room
• But, you see the black paper as darker
• Context is everything

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Perceptual constancy

• These sort of things happen with other systems
  too
• Clocks seem to make a tick tock sound
• We dont only organize, we interpret

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• THEDOGATEMEAT
• (McBurney and Collings, 1984)

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Interpretation

• People born blind that gain sight, what can they
  do?
• Figure ground
• Colours
• Cant tell a sphere from a cube!
• Most of this work had poor control, so monkeys
  and cats have been used too

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Interpretation and Experience

• Same results with cats and monkeys
• Perceptually restricted kittens
• Horizontal or vertical bars
• Cant see what they havent experienced!
• Probably a critical period

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Perceptual adaptation

• When you put prisms on people that shift the
  world say 45 degrees to the right, people adapt
  pretty quickly
• Even upside down!
• Stratton (1896)
• Got sick
• Got confused
• B day 8 he was riding a bike!

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adaptation

• Once he went back to normal he had to re adapt!
• Different depending on species
• Cats people, monkeys, no probs
• Fish, amphibians, not a chance

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Perceptual Set

• When we perceive something we are, in essence,
  organizing it
• People only notice backwards messages when you
  tell them what they are looking for!
• Schemas are important
• Kids see faces as the key
• Adults add the importance of the body
• May even explain some stereotypes

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Perception without sensation or ESP!!!

• Remember, science is skeptical
• Burden of proof is on the claimer
• Keep in mind the idea of chance
• Psychics missed the following
• WWII
• 9/11
• OJ
• Kennedy assassination
• Shuttle disaster

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What psychics did predict

• Satan would be discovered working in a homeless
  shelter, reading to the blind and delivering
  Meals on Wheels
• The Super Bowl would be cancelled after the first
  half because team owners would refuse to cough up
  an extra 10,000 for each player.
• A time tunnel would be created to allow people to
  make a one-way trip back into time. (A way to
  make the return trip is supposed to be discovered
  in 2006.)
• Source, Jan 8, 2002 issue of The Star
• By definition you CANNOT have ESP