Sensation and Perception

Chapter 3

Sensation & Perception

• There are five primary senses:• vision,

• hearing,

• touch,

• taste,

• and smell—

• And several secondary senses including:• balance and pain.

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Chapter Goals

• Learn how the senses detect sensory information

• Learn how this sensory information is actively

• organized

• interpreted

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What is the difference between Sensation and Perception?

Sensation and perception are intimately related in everyday experience, but they are not the same.

• Sensation is the sensory process that • detects visual, auditory, and other sensory stimuli

• and transmits them to the brain.

• Perception is the brain process that:• actively organizes sensory information

• and interpretes sensory information

Sensation furnishes the raw material of sensory experience, while perception provides the finished product.

SensationBasic Definitions

• Absolute Threshold

• Difference Threshold

• Signal Detection Theory

• Transduction

• Sensory Adaptation

Absolute Threshold

• The minimum stimulus intensity that a person can detect.

• Psychologists arbitrarily define the absolute threshold as “the minimum amount of sensory stimulation that can be detected 50% of the time.”

Absolute thresholds for the five primary senses in humans

1. Vision, a candle flame ? mile(s) away on a clear night

2. Hearing, a watch ticking ? feet away;

3. Taste, 1 teaspoon of sugar dissolved in ? of water

4. Smell, a single drop of perfume in a ? .

5. Touch, a bee’s wing falling a distance of ? onto your cheek.

Let’s see how well y’all do at estimating these thresholds

Absolute thresholds for the five primary senses in humans

1. vision, a candle flame 30 miles away on a clear night

2. hearing, a watch ticking 20 feet away

3. taste, 1 teaspoon of sugar dissolved in 2 gallons of water

4. smell, a single drop of perfume in a three-room house

5. touch, a bee’s wing falling a distance of 1 centimeter onto the cheek.

Difference Threshold

• The minimum amount by which stimulus intensity must be changed in order to produce a just noticeable change in sensation.

• The JND is the smallest change in sensation that a person is able to detect 50% of the time.

Weber’s law:

The law states that the just noticeable difference (JND) for all the senses depends on a proportion or percentage of change in a stimulus rather than on a fixed amount of change.

Signal Detection Theory

• A quantitative treatment of detection and discrimination performance, in which the observer is characterized as a maker of statistical decisions.

• The system also prescribes techniques that allow the observer's sensitivity to the stimulus to be estimated independently of the observer's criterion, or preference for particular responses.

• The view that the detection of a sensory stimulus involves both discriminating that stimulus from “noise” and deciding whether the stimulus is actually present. Deciding that a stimulus is present depends partly on the probability that the stimulus will occur and partly on the receiver biases.

• Also called signal decision theory.

Noise

• Two Types:• External

• Internal

• Characteristics• Always present

• Independent of signal

• Level varies

• Sensory systems always attempting to compensate for noise.

Transduction

• The process where by receptors change or convert the sensory stimulation into neural impulses.

• The neural impulses are transmitted to precise locations in the brain

You experience a sensation only when the appropriate part of the brain is stimulated.

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Sensory receptors

• The body’s sense organs contain specialized cells called sensory receptors • They detect and respond to one type of sensory stimuli

• They provide the essential link between the physical sensory world and the brain. • discriminating a stimulus from background “noise”

• deciding whether the stimulus is actually present.

• They can be stimulated by noise but are designed to minimize these effects.

Inappropriate Stimulation

• Can result inunusual sensations!

Sensory Adaptation - Definition

The process of becoming less sensitive to an unchanging sensory stimulus over time.

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Sensory Adaptation

• All of our senses are more receptive, more finely tuned, to changes in sensory stimuli than to sameness.

• After a time the sensory receptors grow accustomed to constant,unchanging levels of stimuli so that we notice them less and less, or not at all.

After Images in Color

•Stare at the eye of the red parrot while you count slowly to 20, then look immediately at one spot in the empty bird cage. •The faint, ghostly image of a blue-green bird will appear in the cage.

•Try the same thing with the green cardinal. •A faint magenta bird will appear in the cage.

Vision

• Light

• Particle or wave?

• Electromagnetic spectrum

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Electromagnetic Spectrum

760 – 380 nm

“Radio” Spectrum• 1,000 Kilo Hertz (KHz) 1 x 103

• 1,000,000 Mega Hertz (MHz) 1 x 106

• 1,000,000,000 Giga Hertz (GHz) 1 x 109

• AM Radio 550 KHz to 1600 KHz• FM Radio 88 MHz to 108 MHz• Cordless Phone, Wi-Fi b 2.5 GHz• Microwave oven 2.5 GHz• New Cordless Phone Wi-Fi a 5 GHz• Modern CPUs 1- 3 GHz

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The Eye

• Cornea, Iris, and

• Pupil

• Lens and Retina

• Rods and Cones

• Retina to Brain

• Visual Cortex

The Pupils

• The pupils respond to emotions as well as to light.

• When a person looks at someone or something highly desirable, the pupils dilate

• The pupils also dilate when a person is frightened, telling a lie, or sexually aroused.

• Pupil size is also related to mental effort—the more intense the mental activity, the larger the pupils become.

That’s My Story Artist: Collin Raye

she said Where you been; so I thought real hardand said I fell asleep in that hammoc in the yard

she said You don't know it boy but you just blew itand I said Well that's my story and I'm stickin' to it

That's my story - Oh that's my storyWell I ain't got a witness and I can't prove itBut that's my story and I'm stickin' to it

(signature)

I got that "deer in the headlight" lookShe read my face like a cover of a bookand said Don't expect me to believe all that staticCause just last week I threw that hammoc in the attic I must've got sucked in, cause you can see right through it And I stutterred well that's my story and I'm stiiiiickin' to it

That's my story - (that's my story)Oh that's my story - (that's my story)Yeah I ain't got a witness and I can't prove itBut that's my story and I'm stickin' to it

(slide solo)

YOU KNOW THE TIME COMES WHEN A WISE MAN KNOWSTHE BEST THING THAT HE CAN DOIS JUST LOOK HER IN THE EYE ANDBEG FOR MERCY AND FACE THE BITTER TRUTH

Well honey me and the boys played cards all nightThere wadn't any hanky panky; not a woman in sightI know I should've called and baby IIII'm really sorryLet's get a cellular phone and you won't have to worry

You know how much I love you and I'm ready to prove itAnd that's my story and I'm stickin' to it

That's my story - (that's my story)Wo that's my story - (that's my story)Well I ain't got a witness and you know I can't prove itBut that's my story and man I'm stickin' to it

You know I ain't gonna do a thing darlin' unless you approve itWell that's my story and I'm stickin' to it

The Lens

• Composed of many thin layers

• Looks like a transparent disc.

• Allows focusing on objects closer than 20 feet. • It flattens as it focuses on objects viewed at a distance

• It becomes more spherical, bulging in the center, as it focuses on close objects.

• This flattening and bulging action of the lens is known as accommodation.

The Lens and Age

• With age, the lens loses some elasticity.

• it loses the ability to change its shape to accommodate for near vision,

• called presbyopia (“old eyes”).

Focus Errors

End Part “a”

Color Vision

• Hue

• Saturation

• Brightness

• Theories

• Trichromatic

• Opponent-Process

News Flash! New receptors detected in the human eye.These receptors apparently send an “illumination level”Signal directly to the brain.

Hearing

• The Ear• Outer Ear

• Middle Ear

• Inner Ear

• Theories of Hearing• Place Theory

• Frequency Theory

http://www.bigchalk.com/cgi-bin/WebObjects/WOPortal.woa/wa/HWCDA/file?fileid=115378&flt=High_School&pathTitles=/Hearing_Balance_(Ear)/Anatomy_of_the_Ear/Ear_--_general_description_diagrams&version=2&tg=Science

Hearing Additional Reading

• Additional Links:• Auditory & vestibular pathways -- tutorial

• Cochlear fluids

• Ear -- general description & diagrams

• Ear -- general information With diagrams

• Inner ear anatomy -- diagram

• Inner ear anatomy -- pictures & descriptions

• Signals From a hair cell

• Virtual tour of the ear -- very comprehensive site

• What Is Earwax?http://www.bigchalk.com/cgi-bin/WebObjects/WOPortal.woa/Homework/High_School/Science/Sensory_Systems/Hearing_Balance_(Ear)/Anatomy_of_the_Ear_54024.html

The Human Ear 2

• Bone Conduction• Description

• Issues for Hearing Aids

• Role of bone conduction in the self-perception of speech

• Testing Babies

• Hearing Loss• Bone Conduction Aids

• NIOSH

• Commercial View

• Rockers!

Rhodes AudiophoneA bone conduction fan made by R. S. Rhodes is shown in this illustration. Assuming a good set of teeth, this fan provided a benefit of up to 30 dB, a gain comparable to listening to someone speaking from a distance of 2 feet rather than 64 feet.

Smell and Taste

• Smell (Olfaction)• Olfactory epithelium

• Olfactory bulbs

• Taste• Taste Buds

• Taste Sensitivities• Non-tasters

• Medium-tasters

• Super-tasters

Skin Sense

• Pain

• The Gate-Control Theory

• Psychological and Cultural Influences

• Endorphins

Gestalt Principals of Perceptual Organization

• Figure-Ground

• Grouping• Similarity• Proximity• Continuity• Closure

• DemonstrationsMain Page

Squirming

http://www.rdc.ab.ca/scottpsych/webite/frames/perception.htm

Interesting Perceptual Links

Figure Ground: The Law

Figure Ground: In Art

Gestalt Principals of Perceptual Organization, Cont.

• Perceptual Constancy

• Shape Constancy

• Brightness Constancy

• Color Constancy

Depth Perception

• Binocular Depth Cues• Convergence

• Binocular Disparity

• Monocular Depth Cues• Interposition• Linear perspective• Relative size• Texture gradient• Atmospheric perspective• Shadow or shading• Motion parallax

Extraordinary Perceptions

• Ambiguous Figures

• Impossible Figures

• Illusions

• Muller-Lyer Illusion

• Ponzo Illusion

• Cultural Differences

Additional Influences on Perception

• Bottom-Up and Top-Down Processing Bottom-up processing approaches emphasize incoming sensory stimuli

and the operations performed on them to build up to a meaningful perceptual representation.

Top-down processing models emphasize the varying degrees to which incoming sensory information is shaped, selected, and influenced by context, expectations, and prior learning.

• Psychological Factors

End of Lecture