SENSATION VS. PERCEPTION

THE BASICS

HOW DO WE CONSTRUCT OUR REPRESENTATIONS OF THE EXTERNAL WORLD?

• 24 hours a day, all kinds of stimuli from the outside world bombard your body. Meanwhile, in a silent, cushioned, inner world, your brain floats in utter darkness. By itself, it sees nothing. It hears nothing. It feels nothing.

• So, how does the world OUT THERE get IN HERE?

SENSATION VS. PERCEPTION

• To represent the world, we must detect physical energy from the environment and convert it into neural signals

THIS PROCESS IS CALLED SENSATION

• When we give MEANING by selecting, organizing and

interpreting our sensations… THIS PROCESS IS CALLED PERCEPTION FOR INSTANCE: Face Blindness (Prosopagnosia) (try recognizing a specific penguin in a group of waddling penguins…)

BOTTOM-UP VS. TOP-DOWN PROCESSING

• BOTTOM-UP = Sensory information is received by receptors on the dendrites of our sensory neurons, and that information is sent to the brain for further processing.

• TOP-DOWN – Our brain also interprets what we sense – we construct perceptions drawing on sensations coming into the brain but also based on our experience… WHAT DO WE EXPECT TO SEE? HEAR? TASTE?

BOTTOM-UP PROCESSING

Analysis of the stimulus begins with the sense receptors and work up to the level

of the brain and mind.

Letter “A” is really a black blotch broken down into features by the brain that we PERCEIEVE as an “A”

TOP-DOWN PROCESSING

Information processing guided by Higher level mental processes as we

construct perceptions, drawing on our Experience and expectations.

T E C T IN T E H T

EXAMPLE OF TOP-DOWN PROCESSING

• Aoccdrnig to rscheearch at Cmabrigde Uinervtisy, it deosn’t mttaer in what oredr the ltteers in a word are, the olny iprmoetnt tihng is that the frist and lsat ltteer be at the rghit pclae. The rset can be a total mses and you can still raed it wouthit a porbelm. This is bcuseae the human mnid deos not raed ervey lteter by istlef, but the word as a wlohe…

SELECTIVE ATTENTION TEST

SCILENTLY

COUNT THE # OF PASSES BY THOSE WEARING WHITE

http://www.youtube.com/watch?v=vJG698U2Mvo

SELECTIVE ATTENTION

• Your conscious awareness focuses, like a flashlight beam, you experience only a limited amount of ALL.

COCKTAIL PARTY EFFECT

SELECTIVE ATTENTION

• 28% of traffic accidents occur when people are chatting on cell phones or texting.

• 25% of teen drivers with cell phones admit to texting while driving.

• fMRI scans show brain activity in areas vital to driving decreased (on average) 37% when a driver is attending to conversation.

• Even hands free phones in cars show individual to be 4 times more at risk than if they were talking to a passenger.

Can we really multi-task?

WHO IS GUILTY!?

Selective Inattention

http://www.youtube.com/watch?v=vBPG_OBgTWg

• Failing to see visible objects when our attention is directed elsewhere…

Change Blindness

• Failing to notice changes in the environment.

• Usually used by magicians

THREE STEPS OF SENSORY SYSTEMS

• RECEIVE sensory stimulation • TRANSFORM stimulation into neural impulses • DELIVER the neural information to our brain

TRANSDUCTION – Conversion of one form of energy into another. (We turn sights, sounds and smells into neural impulses our brain can understand)

WHAT BEES SEE

ABSOLUTE THRESHOLDS

• Gustav Fechner (German scientist/philosopher) studied our awareness of faint stimuli (OUR ABSOLUTE THRESHOLDS) • The minimum stimulation

necessary to detect sensation.

• Thresholds can change over time…

• http://www.youtube.com/watch?v=VxcbppCX6Rk

ABSOLUTE THRESHOLDS

• TASTE: 1 gram of table salt in 500 liters of water

• SMELL: 1 drop of perfume diffused throughout a three-room apartment

• TOUCH: The wing of a bee falling on your cheek from a height of 1cm

• HEARING: The tick of a watch from 6 meters in very quiet conditions

• VISION: A candle flame seen from 50km on a clear, dark night.

SIGNAL DETECTION THEORY

• Theory predicting how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise) • No single absolute threshold • Detection depends partly on a person’s experience,

expectations, motivation, and alertness.

• SIGNAL DETECTION: • What three factors will make it more likely that you

correctly detect a text message?

THE DIFFERENCE THRESHOLD: Just noticeable difference

• The minimum difference a person can detect between any two stimuli half the time.

• Detectable difference increases with the size of the stimulus. • If you add 1 ounce to a 10-ounce weight, you will detect

the difference. • If you add 1 ounce to a 100-ounce weight, you probably

will not.

WEBER’S LAW

• FOR THEIR DIFFERENCE TO BE PERCEPTABLE, TWO STIMULI MUST DIFFER BY CONSTANT PROPORTION-NOT A CONSTANT AMOUNT. • The exact proportion varies depending on the stimulus.

STIMULUS CONSTANT (k)

Light 8%

Weight 2%

Tone 3%

Sensory Adaptation

• Freedom to focus on informative changes in your environment without being distracted by the content chatter of uninformative background stimulation… • Adjustment of senses to level of stimulation they are

receiving • Ever forgotten you are wearing a watch? • Gotten used to a smell?

“WE NEED ABOVE ALL TO KNOW ABOUT CHANGES; NO ONE WANTS OR NEEDS TO BE REMINDED 16

HOURS A DAY THAT HIS SHOES ARE ON” – Neuroscientist David Hubel (1979)

WE MISS A LOT What do we sense?

• At this moment… you and I are being struck by X-rays and radio waves, ultraviolet and infrared lights and sound waves of very high and very low frequencies…

to all these… we are BLIND AND DEAF.

WE PERCEIVE THE WORLD NOT EXACTLY AS IT IS, BUT AS IT IS USEFUL FOR US TO PERCEIVE IT!

FRUIT RINGS!

Shocking News:

All Froot Loop Colors Are Really The Same Flavor

By Laura Northrup January 22, 2014

Colored froot-flavored cereals like Froot Loops come in a rainbow of colors, and those

colors align with different flavors of “froot,” don’t they? Well…no. They do not. All of the

different colors in the box are only that: colors.

We all probably knew this on some level, but it took a post on the Today I Learned

subreddit linking to a 14-year-old Straight Dope column to jolt us out of our state of not

really giving a crap.

Over at Foodbeast, they decided to do some original reporting on this subject, separating

out the different colors of Froot Loops, Fruity Pebbles, and Trix and asking testers to

determine which color they had just tried. The test results? Yeah, they’re all the same

flavor. Kellogg’s confirmed this fact for Cecil Adams. We can at least draw comfort from

the knowledge that Toucan Sam has stayed with the product for its more than 50 years of

existence, even bringing diaper-clad nieces and nephews to work hawking froot-based

breakfast cereals.

FRUIT RINGS!

RESPOND TO THE FOLLOWING QUESTIONS IN YOUR NOTEBOOK

1) Why do individuals perceive differences in taste between the colors? 2) Since smell and taste are most often used at the same time (to detect

“flavor”), is our sense of smell active during this illusory perception? Why or why not?

3) What does this illusions demonstrate about which senses “dominate” others?

4) How does this relate to top-down processing? 5) Which threshold is most applicable to this illusions? One, both, or

neither? 6) Does focusing on specific aspects of the fruit loop (e.g. focusing on the

color) influence the illusion? 7) What other food substances might this illusion apply to? Jelly beans?

Skittles?

INFLUENCES ON PERCEPTION

Perceptual set – Mental predisposition to perceive one thing and not another.

Perceptual Set Cont.

What determines our perceptual set? • Through experience we form concepts (or

schemas) that organize and allow us to interpret unfamiliar information.

• Stereotypes about gender can color perception (if a baby is wearing blue or pink it will determine if we say “he” or “she”

• In what ways was our schema active during the froot ring exersize?

Perceptual Set Cont.

Loch Ness Monster?

Or a Log?

CONTEXT EFFECTS ON PERCEPTION

East Africans perceived the woman as balancing a metal box and family sitting under a tree.

CONTEXT EFFECTS ON PERCEPTION

Cultural background and age will change how you answer this question... Depth perception in images learned?

Which animal is closer?

CONTEXT EFFECTS ON PERCEPTION

Sun Ming Ming = 7’9”… Here towers over the 6’9” UNC player… That UNC player would tower over Mr. Musselman

EMOTION EFFECTS ON PERCEPTION

Emotion • Hearing sad rather than happy music can predispose people

to perceive a sad meaning in spoken homophonic words (mourning instead of morning… die rather than dye)

• Walking destinations look father away to those who have been fatigued by prior exercise.

• Target looks farther away when throwing a heavier object. • BASEBALL appears bigger when hitting well…

EMOTION AND MOTIVATION EFFECTS ON PERCEPTION

Motivation • Desired objects, such as a water bottle when thirsty…

appears closer. (ENERGIZES US TO GET IT) • Spouses who feel loved perceive less threat in stressful

marital events. “He’s just having a bad day…” • SOCCER: Referees who are told that a team has a history of

aggressive behavior will assign more penalty cards after watching video taped fouls.

How does perception influence eyewitness accounts?

http://www.Innocenceproject.org

STOP AND FRISK TACTICS IN NYC

• In 2010, New Yorkers were stopped by the police 601,285 times. • 518,859 were totally innocent (86%) • 315,083 were black (54%) • 189,326 were Latino (33%) • 54,810 were white (9%) • 295,902 were aged 14-24 (49%)

• In 2011, New Yorkers were stopped by the police 685,725 times. • 605,328 were totally innocent (88%) • 350,743 were black (53%) • 223,740 were Latino (34%) • 61,805 were white (9%) • 341,581 were aged 14-24 (51%)

• In 2012, New Yorkers were stopped by the police 532,911 times. • 473,644 were totally innocent (89%) • 284,229 were black (55%) • 165,140 were Latino (32%) • 50,366 were white (10%)

In Sum…

• In 2011, over 120,000 black and Latino kids between 14-18 were stopped and frisked.

• There are only 177,000 black and Latino boys between 14 and 18 in the city.

• It’s not a question of “if?”, but “When?” and “How many times?”

MORE FACTS

• African Americans now constitute nearly 1 million of the total 2.3 million incarcerated population

• African Americans are incarcerated at nearly 6 times the rate of whites

• Together, African American and Hispanics comprised the 58% of all prisoners in 2008, even though African Americans and Hispanics make up approximately one quarter of the US population

• One in six black men had been incarcerated as of 2001. If that trend continues, one in three black males born today can expect to spend time in prison during his lifetime.

• 1 in 100 African American women are in prison.

Visual Organization and Interpretation

GESTALT – In perception, the whole may exceed the sum of its parts.

Visual Organization and Interpretation

A Necker Cube

Our brain does more than register information about the world. BRAIN IS NOT A CAMERA. MIND MATTERS.

Visual Organization and Interpretation

A Necker Cube

Our brain does more than register information about the world. BRAIN IS NOT A CAMERA. MIND MATTERS.

So, what is your mind doing?

Figure-Ground Relationship – Separate figures from surroundings. (For example: words from background, object from table, voice you are listening to from other sounds.)

GROUPING

SIMILARITY PROXIMITY CONTINUITY CLOSURE

DEPTH PERCEPTION “Sometimes I wonder: Why is that Frisbee getting bigger?

And then it hits me.” - Anonymous

THE ABILITY TO SEE OBJECTS IN THREE DIMENSIONS ALTHOUGH THE IMAGES THAT STRIKE THE RETINA ARE TWO-DIMENSIONAL. THIS ALLOWS US TO JUDGE DISTANCE.

Visual Cliff Experiments

DEPTH PERCEPTION

Binocular Cues

• Retinal Disparity – difference between the two images the closer the object. • FINGER CHECK • FLOATING FINGER! • HOLE IN HAND!

• THIS IS HOW THEY MAKE 3-D MOVIES! (They exaggerate retinal disparity by filming with two cameras, eyes only see what was filmed by one of the two cameras)

MORE MONOCULAR CUES

RELATIVE HEIGHT LINEAR PERSPECTIVE

INTERPOSITION LIGHT AND SHADOW RELATIVE SIZE

WE ARE IMPERFECT: WHY DO TRAINS APPEAR TO MOVE SLOWER THAN CARS MOVING THE SAME SPEED?

BASED ON WHAT YOU KNOW HOW DO YOU THINK WE PERCEIVE

MOTION?

Feature Detection PERCEPTUAL CONSTANCY (perceiving objects as unchanging even as illumination and retinal images change)

Color Constancy – perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object.

Feature Detection PERCEPTUAL CONSTANCY (perceiving objects as unchanging even as illumination and retinal images change)

Brightness Constancy Relative Luminance - Believe it or not, these two items are identical in color. - Remove the surrounding context and see what results.

Feature Detection PERCEPTUAL CONSTANCY (perceiving objects as unchanging even as illumination and retinal images change)

SHAPE AND SIZE CONSTANCIES

Feature Detection PERCEPTUAL CONSTANCY (perceiving objects as unchanging even as illumination and retinal images change)

SHAPE AND SIZE CONSTANCIES

Feature Detection IN CONCLUSION

OUR BRAIN CONSTRUCTS OUR PERCEPTIONS

THE MAN WHO LOST HIS BODY

Proprioception

How are sensation and perception related based on this case study?

How we locate sounds Accuracy Of Sound Location

WHY DON’T WE JUST HAVE ONE BIG EAR ON OUR FACE?!!!!

How we locate sounds

Activities: 1. Locating Sound

How we locate sounds…

How we locate sounds Is there a difference in how we perceive LOUDNESS?

• It is not from the intensity of a hair cell’s response….

• Rather, soft tones activate only the few hair cells attuned to its frequency…

• THUS! Brain perceives loudness by the NUMBER of activated cells…

• Loud noises sound the same for those with hearing loss or ‘normal’ hearing… it’s the softer sounds they want amplified.

How we locate sounds THE TWO THEORIES OF PITCH PERCEPTION

• PLACE THEORY. Who can help us understand this?

• What about FREQUENCY THEORY?

• Place theory = High Pitch • Frequency theory = Low Pitch • Volley Principal (combination of both) = In between

How do the senses interact?

Gestalt certainly applies within an isolated sense… What about across modalities?