Perception & Sensation. Complementary Afterimage #1.

Perception&Sensation

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Illusion Haze

Top-down vs. Bottom-up Processing• So far, we have studied the flow of information

from the world into the perceptual system (bottom-up processing). But there is an equally important influence of pre-existing knowledge on our eventual perception of things in the world (top-down processing).

• That is, our prior experiences and expectations have a very strong influence on the things we see. As a result, our perceptions of the world result from a combination of sensory information (data-driven) and pre-existing knowledge (concept-driven).

Prior knowledge guides vision

Face Perception: Which one is Vanna?

Gestalt Grouping Principles

• group nearby figures together

Objects near each other tend to be seen as a unit

Gestalt Grouping Principles: Proximity


• group figures that are similar

Objects similar to each other tend to be seen as a

unit

Gestalt Grouping Principles: Similarity


• Fill in gaps to create a complete, whole object

Gestalt Grouping Principles: Closure

• Fill in gaps to create a complete, whole object

•But, doesn’t the white triangle look whiter than the background?

Gestalt Grouping Principles: Continuity

• Objects that are connected by a smooth curve tend to be seen as a unit

Gestalt Grouping Principles: Common Movement

• Objects moving in the same speed and at the same direction tend to be grouped

•The Hidden Bird Illusion •THIS IS THE APPLET

Gestalt Grouping Principles: Common Movement

• Which direction are the triangles pointing?

Who do you see?

What do you see?

Depth PerceptionHow do we create a 3 dimensional world

from 2 dimensions?

Stereogram

•Cross eyes so that the left eye is looking at the right square and the right looking at the left

•Try ‘fixating’ on an imaginary point in front of the viewing screen at which point you will see three squares- left center and right. The center one will be the stereo image t

Relative Size

• To perceive the size of objects accurately we must also perceive their distance accurately.

• Thus, many visual illusions occur simply because a particular image lacks sufficient depth cues.

Retina Pupil

Image A B

Image A

This figure shows that image size depends upon both object size and distance

Perceived Size and Perceived Depth

The Size-Distance Problem• The Ames room is designed so that the

monocular depth cues give the illusion that the two people are equally far away

Other Size-Distance Illusions• In each of these

examples, the top and bottom lines are actually the same length.

• In each case the top line looks longer.

• Why?

(a) Müller-Lyer illusion

(b) Ponzo illusion

Muller-Lyer Illusion• Perceptual psychologists

have hypothesized that the top horizontal line looks longer because it also looks farther away.

• Specifically, the inward pointing arrows signify that the horizontal line is closest to you, and the outward pointing arrows signify the opposite case.

Ponzo Illusion• Converging lines indicate that top line is farther

away than bottom line

Another Size-Distance Illusion

Linear Perspective

Texture Gradients

The elements of a texture become smaller and smaller as they recede into the distance...another reliable depth cue.

Cues to Depth PerceptionTexture Gradient

Which Triangle is closer?

horizon line

Objects closer to the horizon appear to be farther away...

Relative Height

Cues to Depth PerceptionRelative Height

Size Constancy• Cylinders at positions

A and B are the same size even though their image sizes differ

• The depth cues such as linear perspective and texture help the visual system judge the size accurately

Point A

Point B

Shape Constancy• It is hard to tell if the

figure on the upper right is a trapezoid or a square slanted backward.

• If we add texture, the texture gradient helps us see that it is actually a square.

Attention Demos

The Stroop Effect, part 1

As fast as you can, read the names of the colors

The Stroop Effect, part 2

As fast as you can, (don’t read the word) but read the name of the color of the word.

Attention as a Selector: Find the Green Scarf

Attention as a Selector: Find the Bald Man

Selection Based on Color is Easy

Selection Based on upright vs upside down is not easy

Treisman’s Feature Integration Theory

The following is a demonstration that (a) detecting features is relatively automatic, and (b) that integrating multiple features together and identifying the object is more attention-demanding.

Slap your thigh when yousee the blue line.

Slap your thigh when yousee the horizontal line.

Detecting the blue line was pretty easy, right? Is orientation also easy to detect?

Conjunction Search

• Combination of features (e.g., red AND horizontal)

• Spatial arrangements of features (e.g. black above white)

When targets are defined by:

Identifying Integrated Features

Slap your thigh when you see the bar thatis both horizontal AND blue

So, the conjunction of color and orientation does not pop out.

What about the spatial arrangement of a basic visual feature?

Slap your thigh when you find the blacksquare above the white square:

Can you attend to something without moving your eyes?

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Stare at the cross

+X

QC

M

PE

H

L

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What were the letters that you saw?

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Now, focus on the cross but pay attention to the right side.

+U

FO

S

WN

I

D

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What were the letters?

Attending without moving eyes

• Focus of attention does NOT depend on where your eyes are pointing. We can move our attention independently of our eyes. You can look one way and attend to something that is elsewhere. WHY?

• Attention amplifies our ability to sense information.

• Who has noticed that events seem to slow down when you’re in an accident? Perhaps there’s an expansion of time that occurs when you strongly attend to something?

Attention as a “Selection Mechanism”

What happens to stuff we don’t attend to?

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While looking at the center plus sign, attend to the yellow cross and report whether its vertical or horizontal bar is longer

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Attend Here

Stare at the cross

Which was longer?

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Attend Here

Stare at the cross

Which was longer?

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Attend Here

Stare at the cross

Which was longer?

Who noticed the word “stint”???

Visual Version of Experiment

Task: Is this a word you find generally positive? YES/NO.

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Rabbit

• Subjects have virtually no memory of the unattended objects in a visual version of the dichotic listening task.

• Attention is a gateway to memory. You will not consciously remember stuff that is not attended to.

How Powerful is our ability to attend to something?

How powerful of a selector mechanism is attention?

Some Video Examples

Count the number of passes of the ball by the members on the White Team.

Your Task

Attentional Deficits

Left Visual Neglect

• Inability or difficulty to attend to the left side of visual space or of an object. Caused by lesion in the right parietal lobe.

Line-bisection task

Memory Demos

Sensory Memory Demonstration

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Focus on the cross


X M D N

I F B Z


What were all of the letters?


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Focus on the cross


Q U C L

T J R M


-- -- -- --

-- -- -- --

• Report the letter that was where the arrow points

Visuo-Spatial Sketchpad Demonstration

• Examine this boat for a minute

Visuo-Spatial Sketchpad Demonstration

Was the anchor closer to the front or to the center of the boat?

• Remember these 19 numbers

• Write them down when I’m finished

Chunking: An Example

• Chunk: a category of information that lets you group/organize underlying items.

• Here were the numbers: 1776 2002 24/7 911 22904

Our short term memory capacity is 7 plus or minus 2 chunks of information.

Chunking

Amnesia

• caused by damage to hippocampus and/or surrounding areas

• See the Jeremy video

• Remember the Clive video

Hippocampus

Which is the real penny?

(a) (b) (c) (d) (e)

(f) (g) (h) (i) (j)

(k) (l) (m) (n) (o)

(a) (b) (c) (d) (e)

(f) (g) (h) (i) (j)

(k) (l) (m) (n) (o)

Answer

Class Demonstration

As fast as you can, unscramble the words on the sheet of paper. Turn the page over when you’re finished.

Class Demonstration

Raise your hand if you spelled the last word as

PETAL

Raise your hand if you spelled the last word as

PLATE

• There were two sets of scrambled words preceding the last one. One set was related to kitchen items.

• F I N E K --> KNIFE• K R O F --> FORK• P U C --> CUP• E C U S A R --> SAUCER• L T E P A --> PLATE

All related to

Priming Example #2

• The other set was related to flowers.

• NYPAS --> PANSY• FELA --> LEAF• KTALS --> STALK• LOBSOMS --> BLOSSOMS• L T E P A --> PETAL

All related to

Priming Example #2

• Whether you deciphered LTEPA as “Plate” or as “Petal” was likely influenced by the preceding words.

• These preceding words primed (i.e,. activated) either Plate or Petal.

Priming Example #2

Spend the next 3 minutes writing down as many U.S. states as you can.

A 3 minute Task

Face memory test

Don’t Describe Face

0

20

40

60

80

100P

erc

en

t C

orr

ect

Face Memory Results

Describe FaceDon’t Describe Face

0

20

40

60

80

100P

erc

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t C

orr

ect

Face Memory Results

Why are people worse after describing the face?

Social Demos

Each row contains a pair of adjectives and a “Depends on the situation” response.

I want you to rate George Bush. Put a CHECK (do not circle) next to the item that is most characteristic of George Bush.

The Attribution Scale Task

While driving through a rural area near your home you are stopped by a county police officer who informs you that you have been clocked (with radar) at 38 miles per hours in a 25-mph zone. You believe this information to be accurate. After the policeman leaves, you inspect the citation and find that the details on the summons regarding weather, visibility, time, and location of violation are highly inaccurate. The citation informs you that you may either pay a $50 fine by mail without appearing in court or you must appear in municipal court within the next two weeks to contest the charge.

• Which option would you choose?(a) pay fine (b) contest charge

• What % of the people in this class do you estimate would pay the fine? _______

False Consensus: Tendency to see one’s own choices and opinions as

more common than they are

Class results from last year

They estimated that: _38_% would contest

_62_% would pay

They estimated that: _64_% would contest

_36_% would pay

47% said they would pay fine

53% said they would contest the charge

A Judgment Task

• All subjects perform a boring task for 1 hour, and are then asked to lie to the next subject and say that the experiment was fun and exciting.

• Subjects are paid either $1 or $20 to lie.

• Finally, all subjects privately rate how much they enjoyed the initial task.

• Question: Which subjects reported that they enjoyed the initial task more? Will the subjects paid $1 or those paid $20 rate the task as more enjoyable?

The Implicit Association Test

for more information: www.yale.edu/implicit

Measuring Implicit Stereotypes

abusecrashfilthmurdersicknessaccident

caressfreedomhealthlovepeacecheer

Unpleasant Pleasant

Old People Young People

murderlove

crashfreedompeacefilth

abusecaresscheer

accidenthealth

sickness

LEFT for

Unpleasant

RIGHT for

Pleasant

LEFT for

Old

RIGHT for

Young

LEFT for

Unpleasantor

Old

RIGHT for

Pleasant or

Young

accident

sickness

cheer

murder

peace

LEFT for

Young

RIGHT for

Old

LEFT for

Unpleasantor

Young

RIGHT for

Pleasant or

Old

filth

abuse

love

health

crash

Personality Demos

Social-Cognitive Perspective

• External Locus of Control – the perception that chance or outside forces

beyond one’s personal control determine one’s fate

• Internal Locus of Control – the perception that one controls one’s own fate

On a sheet of paper, write a series of numbers from 1 to 18. For each of the following questions, imagine the situation happening to you, even if it never has. Next, write down the alternative (either A or B) that you prefer. Always record an alternative, even if both are equally preferable.

1. You get very good grades in a course.A. I am a hard worker.B. School work is simple.

2. You feel stronger and more energetic.A. This season of the year makes me feel better.B. I feel better when I exercise.

3. A salesperson is very unpleasant to you.A. I am always polite, even to unpleasant people.B. I can be unpleasant at times.

4. You fail to get the promotion you want.A. I didn’t work as hard as I could have.B. The company suffered a loss and could not

promote anybody.

5. You get picked to represent your neighborhood association at a dinner with the mayor.A. It was my turn to go.B. I showed great interest in going.

6. You read an article that contradicts your views.A. I don’t mind when people disagree with me.B. I never get angry. I always stay calm and collected.

7. A friend is avoiding you.A. Once in a while I am mean to other people.B. Once in a while people are mean to me.

8. Your doctor tells you that despite her recommendations, you still eat too much salt.A. Salt is in everything -- you can’t avoid it.B. I don’t pay much attention to my diet.

9. A friend invites you to dinner.A. My friend feels lonely and wants some company.B. I make pleasant and interesting company.

10. You have a disagreement with a neighbor.A. Once in a while I may lose my temper and get angry.B. I never get angry. I always stay calm and collected.

11. Your spouse/friend says that you don’t share thoughts with him/her.A. I share with my spouse/friend even my most

personal and intimate thoughts.B. I sometimes have ideas that I do not like other

people to know about.

12. Your boss criticizes you.A. He is a critical person.B. I am a poor worker.

13. You make a new friend. A. I am a nice person.B. The people that I meet are nice.

14. A friend who helped you when in need asks to borrow a large sum of money.A. I am always eager to return a favor.B. Lending money to a friend can be a problem.

15. Your spouse/friend yells at you.A. I must have done something wrong to upset him/her.B. He/she has a quick temper.

16. Your friend is making a long argument that you want to comment on.A. I never interrupt others when they are talking.B. I sometimes interrupt others when they are talking.

18. You twist your shoulder in exercise class.A. The instructor pushed us too hard.B. I was not careful in exercise class.

17. You’ve recovered very quickly from the flue.A. I have a good resistance because I take care of my healthB. Fortunately, it was a minor flue.

For questions 1, 4, 7, 13, 15, and 17: give yourself a 1 if you selected A and a 0 if you selected B.

[Alternative A corresponds to an internal locus of control]

For questions 2, 5, 8, 9, 12, and 18: give yourself a 1 if you selected B and 0 if you selected A.

[Alternative B corresponds to an internal locus of control]

Now, add up your total number of points.

Raise your hand if your score is below 6

Raise your hand if your score is below 6

High scores --> associated with an internal locus of control

Low scores --> associated with an external locus of control

Mental Disorders Demos

Dissociative Amnesia

• Marian and her brother were recently victims of a robbery. Marian was not injured, but her brother was killed when he resisted the robbers. Marian is unable to recall any details from the time of the accident until four days later.

Dissociative Amnesia

• Memory loss is the only symptom– Often selective memory loss surrounding

traumatic events

• Key characteristic is that the person still knows their identity.

Dissociative Fugue

• Jay, a high school teacher in New York, disappeared three days after his wife unexpectedly left him for another man. Six months later, he was discovered tending bar in Miami Beach. Calling himself Martin, he claimed to have no recollection of his past life and insisted that he had never been married.

Dissociative Fugue

• Global amnesia with identity replacement – Person develops a new identity

– No recollection of former life

• If fugue wears off– old identity recovers

– new identity is totally forgotten

Dissociative Identity Disorder (DID)

• Norma has frequent memory gaps and cannot account for her whereabouts during certain periods of time. While being interviewed by a psychologist, she began speaking in a childlike voice. She claimed that her name was Donna and that she was only six years old. Moments later, she seemed to revert to her adult voice and had no memory of speaking in a childlike voice or claiming that her name was Donna.

Dissociative Identity Disorder (DID)

• Originally known as “multiple personality disorder”

• 2 or more distinct personalities manifested by the same person at different times

• VERY rare

• Can vary in severity (see video)

Intelligence Demos

• Savant Syndrome– condition in which a person, otherwise limited in

mental ability, has an amazing specific skill• computation

• drawing

Are There Multiple Intelligences?

Savants

George and Charles

Could instantly compute the day of week for any

given date over a span of 80,000 years

But, IQ between 40 -70

Modern intelligence tests

• The Stanford-Binet Scale– intelligence quotient (IQ) = child’s mental age

divided by child’s chronological age and then multiplied by 100

– IQ = MA/CA x 100 (CA = Chronological age)

» E.g., IQ = 13/10 x 100 = 130

– used widely in the US, not as much as previously

Stanford-Binet Scale

The Intelligence Quotient (i.e., MA/CA) is absurd when applied to adults.

Hence, the following joke:

Thinking Demos

Some True/False Questions

1. We notice evidence that contradicts our beliefs more readily than evidence that is consistent with them.

2. In general, people underestimate how much they really know.

3. Only humans seem capable of insight (I.e., the sudden realization of a problem’s solution).

Problem

Write down the names of 6 U.S. cities that are WEST of San Diego.

Here’s the kicker: each city must be in a different state (6 cities from 6 different states.)

Problem

Write down the names of 6 U.S. cities that are WEST of San Diego.

Reno is West ofSan Diego

Falling Object Problem

Spiral Tube Problem

Below are four cards. Each card has a letter on one side and a digit on the other side. You are to verify whether or not the following rule is true: If there is a vowel on one side, there is an even number on the other side. You should verify this rule by turning over 2 cards. Which cards do you choose?

A 2 X 3

Confirmation Bias

Verify Rule: If there is a vowel on one side, there is an even number on the other side.

A 2 X 3

Most people choose “A” and “2”. Why? Because of a confirmation bias.

Answer: A and 3If there’s a vowel on the other side of

the 3 card then the rule is dead

People generally seek evidence that will confirm, not falsify, a hypothesis

Confirmation Bias

It would seem, then that we stink at logic. But . . . .

IF A PERSON IS DRINKING BEER, THEN THE PERSON MUST BE OVER 21 YEARS OF AGE. Select the 2 cards that you definitely need to turn over to determine whether or not they are violating the rule.

Beer 22 Coke 17

• Solve problems and syllogisms by applying information to pre-existing schemas

• More relevant = easier to solve

• The Bottom Line: People are not logic machines who can plug any problem into a logical formula

Representativeness Heuristic

Linda is 31 years old, single, outspoken and very bright. As a student, she was deeply concerned with issues of discrimination and social justice, and also participated in anti-nuclear demonstrations.

What is the probability that Linda is a….?


What is the probability that Linda is a Bank Teller?Write a number between 0 and 100



What is the probability that Linda is a Feminist Bank Teller?

Write a number between 0 and 100


Feminist Bank Tellers are a sub-group of Bank Tellers.

Time after time, people say that there’s a higher likelihood that Linda is a feminist bank teller than that she’s a bank teller. But this is

impossible because:


• Representativeness Heuristic– rule of thumb for judging the likelihood of

things in terms of how well they seem to represent, or match, particular prototypes

– However, it can cause people to generalize too broadly from single cases.

Availability Bias

• Is the letter “k” most likely to occur in the first position of a word or the third position?

• Answer: “k” is 2-3 times more likely to be in the third position

• Most people respond that “k” is more frequent in the first position. Why does this occur?

Availability Heuristic

• Because it is easier to recall words starting with “k” , people overestimate the number of words starting with “k”

Which of the following are more frequent causes of death in the U.S.?

Rate how confident you are in your choice on a scale from 0 (guessing) to 100 (absolutely certain that your choice is correct).

1. All accidents or strokes?confidence rating?

2. Electrocution or asthma?confidence rating?

3. Homicide or diabetes?confidence rating?

4. Lightning or appendicitis?confidence rating?

5. Drowning or Leukemia?confidence rating?

Which of the following are more frequent causes of death in the U.S.?

1. All accidents (55,000) or strokes (102,000)

2. Electrocution (500) or asthma (920)

3. Homicide (9200) or diabetes (19,000)

4. Lightning (52) or appendicitis (440)

5. Drowning (3600) or Leukemia (7100)

• Availability Heuristic– estimating the likelihood of events based on

their availability in memory– if instances come readily to mind (perhaps

because of their vividness), we presume such events are common

– We tend to be overly influenced by events that come easily to mind

Language and Development

Genie spent her first 14 years confined to a small bedroom and weighed just 59 pounds when discovered. She never learned to speak in complete sentences.

Critical Stage & Language

Konrad Lorenz & Imprinting

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