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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