Sensation and Perception

Sensation: your window to the world

Perception: interpreting what comes

in your window.

What is this?

Bottom-Up vs. Top-Down

Processing• If a company is run by it’s

workers, it would have

“bottom-up” management.

• If a boss runs it, it would be

“top-down.”

• Bottom-up used when you

have no prior knowledge =

start @ bottom and work your

way up.

• Top-Down used when you

have prior knowledge = start

@ top & work down

(stereotyping)

• No top down processing =

everything new every day!

Top-Down Processing Example

• I cnduo't bvleiee taht I culod aulaclty uesdtannrd

waht I was rdnaieg. Unisg the icndeblire pweor of the

hmuan mnid, aocdcrnig to rseecrah at Cmabrigde

Uinervtisy, it dseno't mttaer in waht oderr the lterets

in a wrod are, the olny irpoamtnt tihng is taht the

frsit and lsat ltteer be in the rhgit pclae. The rset can

be a taotl mses and you can sitll raed it whoutit a

pboerlm. Tihs is bucseae the huamn mnid deos not

raed ervey ltteer by istlef, but the wrod as a wlohe.

Aaznmig, huh? Yaeh and I awlyas tghhuot slelinpg

was ipmorantt! See if yuor fdreins can raed tihs too.

Problems in Processing

• Prosopagnosia

6

Psychophysics

A study of the relationship between physical characteristics of stimuli and our psychological

experience with them.

Physical WorldPsychological

World

Light Brightness

Sound Volume

Pressure Weight

Sugar Sweet

Thresholds

• Absolute

Thresholds: the minimum stimulation required for us to know that a stimulus has occurred. (at absolute threshold, you will detect the stimulus half of the time (50%)) Gustav Fechner

8

No

Detection

Intensity

AbsoluteThreshold

Detected

YesYesNo No

Observer’s Response

Tell when you (the observer) detect the light.

9

Signal Detection Theory (SDT)

Predicts how and when we detect a faint stimulus (signal) amid background noise (other

stimulation). SDT assumes that there is no single absolute threshold and detection

depends on:

Person’s experienceExpectationsMotivationLevel of fatigue

Carol Lee/ T

ony Stone Im

ages

10

SDT Matrix

Examples: Decision

Pizza Guy

Crying BabyYes No

Signal

Present Hit Miss

AbsentFalse

AlarmCorrect

Rejection

The observer decides whether she hears the tone or not, based on the signal being present or not.

This translates into four outcomes.

Subliminal Messages

• When stimuli are below one’s absolute threshold for conscious awareness.

• Report in 1956: movie theaters are showing

subliminal messages (eat popcorn, drink coca-

cola) to manipulate their viewers. (not true)

• Report later: rock bands are hiding satanic

messages on their records. When you play it

backwards, you hear evil messages

Subliminal Messages

There exists controversy as to whether people actually attend to the information presented below

absolute threshold. Will it impact behavior?Backmasking-Jeff Milner

sample

So, can they get to us????

• - we CAN sense stimuli below our absolute

thresholds (subliminally, unconsicously)

• - we CAN be primed to think certain ways we

FEEL what we do not know and can not describe.

So, can they get to us????

• - we CAN NOT be manipulated to buy stuff.

The effect of the subliminal manipulation is

very short and subtle – it does not have a

lasting effect on people in lab studies. If you

flash “eat” at them and show them a

restaurant commercial, they’ll be a little

hungry for a second, and then forget about it

Weber’s law

• Ernst Weber- 1795-1878

• First quantitative law of

psychology

• There is a constant proportion (not

constant amount) between the

threshold and the stimulus that

can be detected.

• In order for a change in stimulus to

be detected, the amount of

change needed depends on the

present level of stimulation

Difference Threshold

• Just Noticeable Difference (JND) - the

minimum difference between 2 stimuli

required for detection 50% of the time.

Selective Attention

• Your ability to focus your attention on a

particular stimulus

Cocktail-party phenomenon

• The cocktail party effectdescribes the ability to focus one's listening attention on a single talker among a mixture of conversations and background noises, ignoring other conversations.

• Form of selective attention.

Selective Attention

• Distracted Driving – cell users 4xs more likely

to be in accident

• Inattentional Blindness – failing to see visible

objects when your attention is directed

elsewhere (Gorilla Video)

• Change Blindness - failing to notice changes in

the environment (http://www.msnbc.msn.com/id/38154937/ns/dateline_nb

c-the_hansen_files_with_chris_hansen/t/did-you-see/)

Sensory Adaptation

• Decreased responsiveness to stimuli due to constant stimulation.

Do you feel your underwear all day?

Vision

• Our most dominating sense.

• Visual Capture

Transduction• Transforming stimulus energy into neural impulses.

• Information goes from the senses to the thalamus , then to the various areas in the brain.

The spectrum of electromagnetic energy (ROY G BIV)

Phase One: Gathering Light

• The height of a wave gives us it’s intensity (brightness). • The length of the wave gives us it’s hue (color).• ROY G BIV• The longer the wave the more red.• The shorter the wavelength the more violet.

Phase Two: Getting the light in the eye

VISION: Structures of the Eye

• Light enters the eye through the cornea –

protects eye & bends light for focus.

• Light passes through pupil - adjustable

opening in the center of the eye.

• Pupil size (& amt of light) regulated by the iris

- a ring of muscle that forms the colored

portion of the eye around the pupil &

controls the size of the

pupil opening

VISION: Structures, cont.

• Lens – behind pupil; changes shape

(accomodation- changing curvature)to focus

near/far images on the retina

• Retina - the light-sensitive inner surface of the

eye, containing receptor rods and cones plus

layers of neurons that begin the processing of

visual information

Vision Issues

Farsighted Nearsighted Normal

Acuity- the sharpness of vision

�Nearsightedness- nearby objects seen more

clearly than distant objects because distant

objects focus in front of retina

�Farsightedness- faraway objects seen more

clearly than near objects because the image

of near objects is focused behind retina

Demo

• Distribution of Rods & Cones – peripheral

vision & Markers – put focus thing on back

wall, student seated up front

• Predict what will happen – justify results with

what we have learned/you have read.

Retina’s Reaction to Light-

Receptors-2 Types: RODS & CONES

� Rods (120 million)

� peripheral retina

� detect black, white and gray

� twilight or low light

� Cones (6 million)

� near center of retina

� fine detail and color vision

� daylight or well-lit conditions

Fovea- central point in the retina, around which the

eye’s cones cluster

Phase Three: Transduction

Transduction Continued

• Order is Rods/Cones to Bipolar cells to Ganglion cells to Optic Nerve.

• Sends info to thalamus-

• Then sent to cerebral cortexes.

• Where the optic nerves cross is called the optic chasm.

Herman Grid

• Ganglion cell

activity causes

this.

Blind Spot Activity

• Pass out blind spot sheet

• How does this work?

• The blind spot occurs is the location in the

retina where the optic nerve exits to the brain,

there are no receptors there

• What our brain does, typically, is fill in that

missing piece based on what it estimates to be

there

Phase Four: In the Brain• Goes to the Visual Cortex located in the Occipital Lobe of the Cerebral Cortex.

• Feature Detectors (�illusory contours)

• Parallel Processing-simultaneous

processing of

several aspects of a

problem

We have specific cells that see the lines, motion, curves and other features of this image. These cells are called feature detectors.

Color Vision

Two Major Theories

Young-Helmholtz Trichromatic Theory

Three types of cones:

• Red

• Blue

• Green

• These three types of cones can make millions of combinations of colors.

• Does not explain afterimages or color blindness well.

Color-Deficiency

Opponent-Process theory

The sensory receptors come in pairs.

• Red/Green

• Yellow/Blue

• Black/White

• If one color is stimulated, the other is inhibited.

Afterimages

Why do you see the after image?

• Opponent processes explain this: you tire one

response color by staring at it.

• When you stare at white, the opponent color

is the only color firing normally.

Audition: aka Hearing

Our auditory sense

Audition: aka Hearing

� Frequency

� the number of complete wavelengths that pass

a point in a given time

� Pitch

� a tone’s highness or lowness

� depends on frequency

We hear sound WAVES

• The height of the wave gives us the amplitude of the sound.

• The frequency of the wave gives us the pitch if the sound.• EG A piccolo produces much shorter, faster sound waves

than a tuba.

The Intensity of Some

Common Sounds

The EarHandout Diagram

The Ear

� Middle Ear� chamber between eardrum and cochlea

containing three tiny bones (hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window

� Inner Ear� innermost part of the ear, contining the cochlea,

semicurcular canals, and vestibular sacs

� Cochlea� coiled, bony, fluid-filled tube in the inner ear

through which sound waves trigger nerve impulses.

Transduction in the ear• Sound waves hit the eardrumthen hammer then anvil then stirrup then oval window.

• Everything is just vibrating.• Then the cochlea vibrates.• The cochlea is lined with mucus called basilar membrane.

• In basilar membrane there are hair cells.

• When hair cells vibrate they turn vibrations into neural impulses which are called organ of Corti.

• Sent then to thalamus up auditory nerve.

It is all about the vibrations!!!

Demo: Fox 40 Whistle

Pitch Theories

Place Theory and Frequency Theory

Place Theory

• Different hairs vibrate in the cochlea when they receive different pitches.

• So some hairs vibrate when they hear high and other vibrate when they hear low pitches.

Frequency Theory

• All the hairs vibrate but at different speeds.

How We Locate Sounds – Demo clicker

Deafness

Conduction Deafness

• Something goes wrong with the sound and the vibration on the way to the cochlea.

• You can replace the bones or get a hearing aid to help.

Nerve (sensorineural) Deafness

• The hair cells in the cochlea get damaged.

• Loud noises can cause this type of deafness.

• NO WAY to replace the hairs.

• Cochlea implant is possible.

Synesthesia

• http://www.youtube.com/watch?v=a3DbScY8

Ais

Touch

• Receptors located in our skin.

� Skin Sensations

� pressure

� only skin sensation with identifiable receptors

� warmth

� cold

� pain

Touch - PAIN

• Gate Control Theory of Pain

� theory that the spinal cord

contains a neurological

“gate” that blocks pain

signals or allows them to

pass on to the brain

� “gate” opened by the activity

of pain signals traveling up

small nerve fibers

� “gate” closed by activity in

larger fibers or by

information coming from the

brain

http://www.youtube.com/watch?v=1vL

sZ_dXFAg

Taste

• We have bumps on our tongue called papillae.

• Taste buds are located on the papillae (they are actually all over the mouth).

• Sweet, salty, sour, bitter, umami.

TASTE

� Sensory Interaction

� the principle that one sense may influence

another

� as when the smell of food influences its taste

Smell

Receptor cells in

olfactory membraneNasal

passage

Olfactory

bulb

Olfactory

nerve

Smell

• Memories linked to smell – hotline between

olfactory area and limbic system (assoc with

memory and emotion)

Vestibular Sense

• Tells us where our body is oriented in space.

• Our sense of balance.

• Located in our semicircular canals in our ears.

Kinesthetic Sense

• Tells us where our body parts are.

• Receptors located in our muscles and joints.

Without the kinesthetic sense you could not touch the button to make copies of your buttocks.

The 10 Senses

• Vision Pain

• Hearing Hot (warm)

• Taste Cold

• Smell Vestibular

• Pressure Kinesthesis

Cocktail-party phenomenon

• The cocktail party effectdescribes the ability to focus one's listening attention on a single talker among a mixture of conversations and background noises, ignoring other conversations.

• Form of selective attention.