Sensation vs. Perception

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Sensation vs. Perception

• Sensation a process by which our sensory
  receptors and nervous system receive and
  represent stimulus energy
• Sensation is the raw data our brain takes in from
  the environment.

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Sensation vs. Perception

• Perception a process of organizing and
  interpreting sensory information, enabling us to
  recognize meaningful objects and events.
• Perception makes sense of sensation.
• Both involve one continuous process and
  perceptual failure may occur at any level whether
  at the sensory level or the perceptual
  interpretation level.
• Example Prosopagnosia

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Bottom Up vs. Top Down Processing

• Bottom Up Processing analysis that begins with
  the sense receptors and works up to the brains
  integration of sensory information.
• Involves making sense of raw sensation.
• Top Down Processing Information processing
  guided by higher-level mental processes
• As when we construct perceptions drawing on our
  experience and expectations.
• Our expectations and experiences shape how we
  perceive information.

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Prosopagnosia

• Is a condition

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Bottom Up vs. Top Down
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Bottom Up Vs. Top Down

• What do you see?

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Bottom Up vs. Top DownOLD WITCH IN PICTURE

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Psychophysics

• Psychophysics study of the relationship between
  physical characteristics of stimuli and our
  psychological experience of them
• Light- brightness
• Sound- volume
• Pressure- weight
• Taste- sweetness

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Sensation Thresholds

• Absolute Threshold minimum stimulation needed
  to detect a particular stimulus.
• Usually defined as the stimulus needed for
  detection 50 of the time.

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Subliminal Messages

• What does the research say?
• http//jeffmilner.com/backmasking.htm
• http//www.nlpweekly.com/?p527
• Homework

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Sensation Thresholds

• Difference Threshold or (JND-Just Noticeable
  Difference) the minimum difference that a
  person can detect between two stimuli. What does
  it take to tell two similar stimuli apart?
• Webers Law to perceive a difference between
  two stimuli, they must differ by a constant
  proportion
• light intensity- 8
• weight- 2
• tone frequency- 0.3

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Sensation Thresholds

• Signal Detection Theory predicts how and when we
  detect the presence of a faint stimulus (signal)
  amid background stimulation (noise)
• Assumes that there is no single absolute
  threshold
• What might a persons detection of a stimulus
  depend on?

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Sensory Adaptation

• Sensory Adaptation diminished sensitivity with
  constant stimulation.
• Ocean
• Bad Smell
• Ads- cut in, zoom, fade out

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Sensory Adaptation and Vision
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The Science of Energy and Sensation

• Transduction- conversion of one form of energy
  to another.
• Wavelength- the distance from the peak of one
  wave to the peak of the next.
• Hue- dimension of color determined by wavelength
  of lightcolor is matter of how far wavelengths
  are apart.
• Intensity- amount of energy in a wave determined
  by amplitude.
• brightness
• loudness

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Human Vision Represents Narrow Part of All
Electromagnetic Energy
ROY G. BIV Starts from longer to shorter
wavelengths. Rlongest Vshortest
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Vision Physical Property of Waves
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Biology of Vision Step One Light Enters the Eye

• 1.) Light enters the eye through the cornea
  (transparent protector) and the light passes
  through the pupil (small opening/hole). The
  size of the opening (pupil) is regulated by the
  iris the colored portion of your eye that is a
  muscular tissue which widens or constricts the
  pupil causing either more or less light to get in.

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Biology of Vision Step Two An Image is Produced

• 2.) Behind the pupil, the lens, a transparent
  structure, changes its curvature in a process
  called accomodation, and focuses the light rays
  into an image on the light-sensitive back surface
  called the retina where image is focuses.

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Biology of Vision Step Three Chemical Reactions
and Sight

• 3.) Image coming through activates
  photoreceptors in the retina called rods and
  cones. As rods and cones set off chemical
  reactions they form a synapse with bipolar cells
  which forms a synapse with ganglion cells which
  fire action potentials along the optic nerve
  that carries this information to be processed by
  the Thalamus (sensory switchboard) that sends
  information to the visual cortex which resides in
  the occipital lobe. The brain then constructs
  what you are seeing and turns image right side up.

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Parts of Retina

• Blind Spot part of retina where optic nerve
  leaves the eyeno receptor cells are there.
  Brain fills information in with info from other
  eye.
• Fovea central focal point of the retina, where
  cones cluster.
• Cones located near center of retina (fovea)
• fine detail and color vision
• daylight or well-lit conditions
• Rods located near peripheral retina
• detect black, white and gray
• twilight or low light

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Rods Cones
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Errors In Vision

• Acuity the sharpness of vision
• Nearsightedness
• nearby objects seen more clearly
• lens focuses image of distant objects in front of
  retina
• Farsightedness
• faraway objects seen more clearly
• lens focuses near objects behind retina

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Errors in Vision

• Normal Nearsighted
  Farsighted Vision
  Vision Vision

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Visual Involves Parallel Processing

• Parallel vs. Serial parallel means simultaneous
  while serial means step by step. Our brains
  process are often parallel processes while
  computers work serially.
• Parallel Processing simultaneous processing of
  several dimensions through multiple pathways.
  Different part of brain for
• color
• motion
• form
• depth

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Parallel Processing

• Feature Detectors neurons in the visual cortex
  respond to specific features
• shape
• angle
• movement

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How The Brain Perceives
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Visual Information Processing

• Trichromatic (three color) Theory
• Young and Helmholtz
• three different retinal color receptors
• red
• green
• blue

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Color Deficient Syndrome

• People who suffer red-green blindness have
  trouble perceiving the number within the design

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Visual Information Processing

• Opponent-Process Theory- opposing retinal
  processes enable color vision. Example Jesus On
  Title Slide.
• ON OFF
• red green
• green red
• blue yellow
• yellow blue
• black white
• white black

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Stare At This for 30 Seconds Then Look At A White
Surface