SensationSensationandand

PerceptionPerception

What do you feel? You probably feel your What do you feel? You probably feel your rear against your seat.rear against your seat.

Ok, now take a whiff around the room – Ok, now take a whiff around the room – different odors are entering your nose different odors are entering your nose (hopefully something pleasant)(hopefully something pleasant)

Now listen really closely, what do you hear? Now listen really closely, what do you hear? – probably the hum from the computer or – probably the hum from the computer or that guy next to you snoringthat guy next to you snoring

Now try to taste what’s in your mouth. – Now try to taste what’s in your mouth. – maybe you can dig out a piece of food from maybe you can dig out a piece of food from your breakfast or maybe you have that your breakfast or maybe you have that morning breath flavor funk going on.morning breath flavor funk going on.

Regardless, at this moment, in some Regardless, at this moment, in some distorted way, you are using all of your distorted way, you are using all of your senses.senses.

Sensation

• The process by which our sensory receptors (sense organs) receive stimulus from the environment.

• What that means is when your body (through our senses) takes in information from everything around us, we are experiencing sensation.

Perception

• The process of organizing and interpreting sensory information

So So sensationsensation is is taking the stuff from outside of us and taking the stuff from outside of us and

bringing it inside our bodies bringing it inside our bodies

and and perceptionperception is is our body trying to understanding and our body trying to understanding and

organizing what we take in.organizing what we take in.

SensationSensation

Important Important ConceptsConcepts

So how does your brain make sense of the So how does your brain make sense of the world and form what you understand as world and form what you understand as

reality?reality? Bottom-Up Processing Bottom-Up Processing (data driven)(data driven)

Our sense of reality starts with our sensations and Our sense of reality starts with our sensations and work up to the brainwork up to the brain

The brain takes the info from the senses and we The brain takes the info from the senses and we develop a sense of realitydevelop a sense of reality

Top-Down Processing Top-Down Processing (experience driven)(experience driven) Our sense of reality begins with our prior experiences Our sense of reality begins with our prior experiences The brain takes our prior experiences and new The brain takes our prior experiences and new

current info and together we develop a sense of current info and together we develop a sense of realityreality

(the brain compares what you are currently seeing with what (the brain compares what you are currently seeing with what you have experienced before)you have experienced before)

Bottom-UpProcessing

Detection viaReceptor cells

(flicker, crackle,Smell

TransmissionTo brain

Change of energyInto information

Organization andInterpretation

Experience, motivation,And expectations (fond

Campfire memories,Expectations of warmth

And friendshipTop-DownProcessing

Behavior, thoughtsAnd emotions(move nearer,warm hands,

Feel comfortable

OutputProcessing(perception)

Input(sensation)

Bottom-Up Processing

• Let’s start off with an important term – transduction

• The process by which our body transforms light, sound, touch, etc. into neural impulses that our brain can understand

TransductionConversion of one form of energy to

another. Stimulus energies changed to neural impulses.

Light Eyes Transduction Neural messages

What you consciously see

Sensory Adaptation• Diminished sensory sensitivity as a

result of constant stimulation.

When you first go into a restaurant you probably notice lots of different food smells. However, the longer you stay the less you notice them. The smells don’t disappear – people just become less sensitive to them.

Do you feel every sensation going on around you??

Can you recall a recent time when, your attention

focused on one thing, you were oblivious to

something else (perhaps to pain, to someone’s

approach, or to background music)?

Selective Attention•The ability to focus on some bits

of sensory information and ignore others

Illusionists hope you have very bad selective attention

Green Dot

Helps us screen out irrelevant stimuli and focus on relevant information

Inattentional Blindness

Inattentional Blindness Failing to see visible objects when we are focusing our attention elsewhere

An example of selective attention is:

The ability to listen to one voice among many.

Cocktail Party Effect

Sensory Interaction

•One sense may influence another

•Smell may influence taste

What if we could sense everything?

Life would hurt.

So we can only take in a window of what is out there.

Psychophysics: the study of the relationship between physical stimuli and our psychological experiences to them. – i.e. is blue really blue??

Measuring the SensesMeasuring the Senses

• Psychologists assess the accuracy of the senses in two ways

Measuring thresholds

Applying the signal detection theorysignal detection theory

ThresholdsThresholds are the idea that our

senses have basic limits.

• There are two types of thresholds– Absolute threshold– Difference threshold (or just noticeable

difference)

Absolute ThresholdAbsolute Threshold The smallest amount of stimulus that a person The smallest amount of stimulus that a person

can reliably detectcan reliably detect If you can just barely hear a sound – then that If you can just barely hear a sound – then that

is your absolute threshold for soundis your absolute threshold for sound

Sight = a candle flame seen at 30 miles on a dark clear night Vision Threshold

Hearing = the tick of a watch under quiet conditions at 20 feet

Taste = 1 teaspoon of sugar in 2 gallons of waterSmell = 1 drop of perfume diffused in a small houseTouch = the wing of a bee falling on your cheek from a distance of 1 cm

Some common thresholds

Difference Threshold• The smallest amount of change

needed in a stimulus before we notice the change

• Also known as Just Noticeable Difference (jnd)

Can you tell the difference??Can you tell the difference??

Weber’s Law• Used to measure the difference threshold• The idea that, to perceive a difference between

two stimuli, the change must be proportional to the original intensity of the stimulus– What???– The more intense the stimulus, the more it will need

to change before we notice the difference.

Weight – 10%

Hearing – 5%

Vision – 8%How do businesses use Weber’s Law?? - Movie theater example

Signal Detection Theory• This theory examines how outside

influences effect our sensing of stimuli• The theory says …

– Absolute thresholds are not really absolute– Things like motivation or physical state can

effect what we sense.

Signal Detection Theory Cont.

• It is the belief that people respond differently to the same signal and the same person may detect a particular signal at one time but not another

• For example – if I am really hungry for meat, I am more likely to smell a hamburger than if I was not

– If I think I smell a hamburger, but it is not really there, that is called a false positive (perceiving stimuli that is not there)

– If a hamburger is grilling right in front of me but I fail to smell it, that is called a false negative (not perceiving a stimulus that is present)Which one is worse??

Subliminal Stimulation• Below one’s absolute

threshold or conscious awareness.

Does this work?

Yes and No

• A few studies did show some small emotional reactivity (called priming a response).

• However, the effects are subtle and fleeting.

SensationsSensations

We will be covering the following We will be covering the following sensessensesVisionVisionHearingHearingTouchTouchTasteTasteSmellSmellBody Position and MovementBody Position and Movement

Of The 5 Senses, Which Would You Choose To Lose? Why?

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SenseSense What Stimulates UsWhat Gets Stimulated

Hearing

Vision

Touch

Pain

Sound Waves

Smell

Taste

Light Waves

Potentially harmful stimuli

Molecules dissolved in fluid

Molecules dissolved in fluid

Pressure on Skin

Pressure-sensitive hair cells in cochlea of inner ear

Light-sensitive rods and cones in retina of eye

Sensitive ends of touch neurons in skin

Sensitive ends of pain neurons in skin and other tissue

Taste cells in taste buds on the tongue

Sensitive ends of olfactory neurons in the mucous membranes