10/16/2015 Sensation and Perception · Sensation and Perception Our Link With the World Sensation:...
Transcript of 10/16/2015 Sensation and Perception · Sensation and Perception Our Link With the World Sensation:...
10/16/2015
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Sensation and Perception Our Link With the World
Sensation: outside stimulus is detected by specialized receptors and transduced into electrical messages to be
sent to brain
Perception: brain tries to organize, interpret & recognize what’s being sensed Receptors in the eye are sensitive to a small range of wavelengths
of electromagnetic energy – the “visible spectrum”
Page 94
Shorter wavelengths give
us “blue” experience
Longer wavelengths give
us “red” experience
Page 96
Receptors are the deepest layer!!
You are responsible for knowing the parts of
the eye and their
functions (p 94-95)
Two Kinds of Photoreceptors:Rods vs Cones
• ~120 million/eye
• more in periphery
• very sensitive – respond even in dim lighting
• ~100 rods share same optic nerve fiber to brain
• night vision
• ~6 million/eye
• most in fovea (center)region
• need bright light to work
• have more private lines to brain- good for detail vision or “visual acuity”
• 3 different types of cones -provide color vision
2 Theories of Color Vision (p. 98-99)Proposed in 1800’s
• Trichromatic Theory – 3 types of color (R,G,B) receptors work together to represent all colors of the spectrum.
• Opponent Process Theory – cells in the visual pathway receive input about pairs of colors (R-G or B-Y). One color makes them fire faster, the other makes them fire slower.
Color “Opposites” on the
Color Wheel
“Afterimages” of strong
visual stimuli are in
opposite colors
Cones• Now have actual
evidence for 3 different types of cones in retina, absorbing different ranges of wavelengths
• Supports Trichromatic Theory
• Some people don’t have all types of cones
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What Do You See?Tests for Normal Color Vision
• Inability to distinguish red from green is the most common type of “color blindness”
Thinking About Sound Waves
Waves vary in how many molecules are moved
(amplitude) and how many waves per second (frequency)Page 100 in book
Measured in decibels
The Ear
• https://www.youtube.com/watch?v=flIAxGsV1q0A diagrammatic tour through the ear
• http://www.youtube.com/watch?v=U_HUgzhmq4U Real life views of the auditory structures
You are
responsible for
knowing the
parts of the ear
and their
functions (p
127)
Fluid Motion in Cochlea
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Audition (Hearing)
• ~ 15,000 auditory receptors called hair cells lined up on the long basilar membrane inside each cochlea
• Movements of membrane as fluid waves ripple thru cochlea result in bending of hair cells which triggers their electrical messages
How Do We Hear Different Pitches (20-20,000) Hz?• Frequency theory – for low frequency deep pitches the
auditory nerve fires at the same freq as the pitch we are hearing, telling the brain the pitch
• BUT – nerves can’t fire faster than 1000/sec so this only works for low freq sounds
• Place Theory - for higher pitches, diff. pitches maximallystimulate different places along the basilar membrane.
• This “place” in the cochlea tells the brain the pitch.
• Visualize how different pitches stimulate different spots
• https://www.youtube.com/watch?v=dyenMluFaUw
Loud Sounds“Trample” Hair Cells
• Repeated exposure can cause permanent damage
• Researchers are really worried about this “ear-bud” generation
• Expect more rapid aging of your ears if they are abused
• Test your hearing – have you already lost your upper range?
http://www.youtube.com/watch?v=IrewnzQYrPI
http://www.youtube.com/watch?v=Irewnz
QYrPI
https://www.youtube.com/watch?v=VxcbppCX6Rk
Types of Deafness (p. 115)• Conduction Deafness – auditory stimulus does not pass
normally through auditory canal, ear drum or middle ear.
• Neural Deafness – deafness due to damage to hair cells or auditory nerve.
2 Chemical Senses
• Taste
• Smell (Olfaction)
Fungiform Papillae(bumps on tongue)
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Tastes Buds on Sides of Papillae
We only have taste receptors for these qualities: sweet, sour,
salty, bitter, and “umami” (meaty flavor). Most of what we call
“flavors” (orange, grape, bubble gum, etc) depend on smell
more than taste.
Olfactory Receptors Located High Up in Nasal Passages
• These receptors also have cilia – in this case to be exposed to odorous molecules in the air we sniff.
Smell
Olfactory receptors
send their axons
thru the skull to
brain. This
arrangement puts
them at risk of
being torn off of
brain in a head
injury situation.
Olfaction (Smell)
• Humans may not think that their olfactory sense is very sensitive or important.
• But we have 6-10 million olfactory receptors at the top of each nostril in humans (there are about 10-20 times as many in dogs)
• More than 1000 different types of olfactory receptors to detect different shaped molecules!
• Some of the impact of olfactory stimuli may be at the unconscious level via pheromones that affect our physiology & behavior.
Olfaction• About 1 in 100 suffer serious anosmia (loss of sense of
smell); many more have partial anosmias where they lack the ability to detect certain odors.
• 75-90% of those with Alzheimer’s have decreased olfactory sensitivity (may be useful in early diagnosis)
• Women have a better sense of smell than men, with peak olfaction at time of ovulation, and may use olfaction when choosing mates.
Pheromones
• Pheromone: chemical signal from 1 member of species which affects biology and/or behavior of another member of species.
• Female mice housed together frequently stop having an estrus cycle. The presence or the smell of a mature male induces ovulation and a normal estrus cycle.
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MenstrualSynchrony: A Pheromone Example in Humans
• Women living together not on hormonal birth control tend to have their cycles come into synchrony because of pheromones.
Gestalt Psychology
• Studied what organizing principles our perceptual system uses to turn a million pixels of visual input into meaningful whole figures
The Perception Regions of Brain Must:
Select what sensory input to focus attention on
Organize the input from millions of receptors (“bottom–up processing”)
Interpret/recognize input in terms of your past experience, expectancies, context (“top-down processing”)
This means that perception is very individualized.
What you experience is NOT just the result of sensory input.
Perceptual Processing Tasks• Pick out the figure or foreground from the background
• Identify patterns, continuous lines, what things go together, the “whole” or the “Gestalt”
• Match input to your memories of past sensory experiences (recognition)
• Maintain that recognition even if angle of view, lighting, or distance changes (perceptual constancies)
• Distinguish depth, distance, 3-dimensions
Multiple cues
(brightness, shading,
borders, decoration) to
identify the vase as the
figure against the dark
background.
Without enough cues,
figure/ground task
becomes more difficult.
Figure/Ground Face-Vase Illusion –A Reversible Figure(not clear what is figure vs ground)
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Necker Cube –Another Reversible Figure• Is the red dot at the front of the cube or the back
corner of the cube? Can you make it switch?
Perception Depends on Context, Past Experience, Expectations or “Perceptual Set”
A context example-
what is the middle
stimulus?
Perception Depends on Context, Past Experience, Expectations or “Perceptual Set”: What if we change the “context”?
• http://www.youtube.com/watch?v=BnKV4-jGhec&feature=related
An expectations example:
An Auditory Example of Top-Down Processing Influencing Perception
• “Backmasking” – are there hidden messages in a piece of music played backwards?
• http://www.albinoblacksheep.com/flash/queen
Monocular (“one eye”) Cues or “Artist’s Cues” for Depth
• Relative Height
• Relative Size
• Texture Gradient
• Linear Perspective
• Aerial or Atmospheric Perspective
• Interposition
• Motion Parallax or Relative Motion
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Relative Size & Height Cues
Texture gradient cues
Interposition
Cues
(one thing
blocks view
of another)
Parallel lines appear to converge on horizon)
Distant things are fuzzier, less distinct
Closer objects appear to pass by quickly
Motion Parallax
We also have internal cues for depththat come from having 2 eyes
Binocular (2 eye) Cues • Convergence of Eyes
• As objects get close to us, our eyes point inward. Perception system uses this muscle feedback as depth cue.
• Retinal or Binocular Disparity• Difference between what right eye sees and what left eye sees is used to
determine depth perception and seeing objects as 3 dimensional.
Perceptual Constancy
• We perceive that objects remain constant, even though the retinal image continually varies as we or the object moves or the environmental conditions (like lighting) change. • Size constancy(as object moves closer or farther)
• Shape constancy (as our angle of viewing changes)
• Color constancy (as lighting changes)
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Manipulating Your Perceptions: Illusions (when the cues we normally usedeceive us)
Impossible Triangle
Impossible Trident Ames Room
http://www.youtube.com/watch?v=5ic7QGjGEX8
http://www.youtube.com/watch?v=Ttd0YjXF0no
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Because of size constancy and depth perception we are not bothered by the difference in the size of the guy in the
white shirt.
• As long as I don’t change his position
You Can Recognizes These As Faces Even When Upside Down
But while getting the “Gestalt” you missed these details:
Do You Know What Each of These Researchers Did?• Pavlov
• Watson
• Thorndike
• Skinner
• Bandura
• Tolman
• Kohler