Ch. 8: Categories and concepts
Concept and Knowledge
• Topic:
– How do we store and manipulate a concept in
the brain?
Concepts, beliefs and behavior
Concept/belief and action
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Mother Teresa
Timothy McVeigh (Oklahoma bomber)
Ted Kaczynski (the unabomber)
Osama bin Laden
Mahatma Gandhi
Nelson Mandela
George Washington
74 men and women died in Waco, TX
Bill Clinton
Psychiatric disorders
• Anxiety disorder
– Is created by an lingering belief on something
threatening happens
• Maniac depression
– Disbelief on one’s ability, fate, etc.
Political language:
• Compassionate conservative
• support the rich but also, supposedly, generous to the poor.
• Limousine liberal
• extremely rich but appreciate liberal ideas.
• War president
• A president who deals with war.
• Death tax
• Inheritance tax
• Pro-life
• a political position against abortion
• Pro-choice
• a political position that supports abortion
• Insurance premium
• Insurance fee
• Tax cuts
• cutting taxes of one group and raising taxes for others
Stereotype
• Ethnic conflicts
Concept and memory?
• Are they two different things?
What is the structure of
“concept”?
This is the today’s topic.
Demonstration:
• Tell me what you see as accurately as
possible.
Why do you say “hammer”?
• Why not “hand tool”?
• Or why not the $15 hammer I bought in Wal
Mart last Wednesday?
• Why not “animal”?
• Or why not “vegetable”?
What is “concept”?
• I don’t know
– But maybe concept we have is related to the
way we categorize things
Concept --> categories
• In order to study “concept”, I’ll talk about
“categories” .
There are trillions of categories.
• Animals, dogs, cats, birds, mammals,
furniture, desks, chairs, tables, books,
magazines…..
• Trees, grass, weed, stones, rocks, sand,
mountains, rivers,…..
• Games, sports, hobbies, …
• school, banks, shops, restaurants,
supermarkets,
– Nazi!! Fascists!! Terrorists, racists, sexists,
pacifists, philanthropists, sophists, aristocrats,
workers, bankers, lawyers, accountants,
teachers, students, disciples, masters, gurus,
beggars, bigots,
– Party animals, beasts!!, dogs!!,
– CEO, CFO, CIO, UFO, evp, vip,
– IC (Indian Chief)
Ad hoc categories
– People I adore, People I admire, People I hang
around, People I need, People I avoid.
– Things I love, Things I enjoy, Places I love,
Food I hate, music I like, movies I enjoy
– countries I want to visit, restaurants I avoid
• Circles, triangles, squares, dots, lines,
rectangles, plane,
• 1, 2, 3, 4, 100, 120,
• A, B, C, D,…..
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The format of representing a
category
When we say “dog,” what’s
going on in our mind?
• What is the mental representation of
“categories”?
• How do we distinguish in our mind
– a dog from a cat?
– a circle from a triangle?
• What’s going on?
– What is the structure?
– What is the neural connections?
Which woman looks more
attractive/friendly/pleasant/capable?
Concepts
• What determines “dog” vs. “cat” or “table”
vs. “vegetable”, “game” vs. “sport”,…..
Classical view
• Necessary & sufficient rule
– we store definitions.
Circle --> an area circumscribed by an
equidistant curve.
Triangles --> an area circumscribed by three
straight lines having three angles………..
A circle of friends, Dupon circle, Columbus
Circle, Circle line
Bermuda triangles, triangle defense (Chicago Bulls)
• Brother, sister, mother, father, uncle,
• Some concepts may be organized with specific
rules.
• But how about other categories?
– Game?
• Basketball, softball, horse race, chess, a wheel of fortune,
survivor, roulette, love affair, computer game, Super Mario?
– furniture
• desk, table, rug? Bed? Computer? TV?
Alternative view
Concepts and categories
– Pink is basically red.
– 99 is almost 100.
– Orange is sort of yellow.
– Austin is like Rome.
– San Antonio is very much like Mexico.
– Pita can be bread.
Concepts and categories II
– Red is basically pink.
– 100 is almost 99.
– Yellow is almost orange.
– Rome is like Austin.
– Mexico is very much like San Antonio.
– Bread can be pita.
Birds: which one looks more like “bird”?
Which desk is the best example of “desk”?
Which game is the best example of
“game”?
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Baseball
Chess
Basketball
Politics
Football
Golf
One-night love affair
Snowboarding
Checker
Ping-Pong
Slot machine
Poker
Mahjong
Horse racing
NASCAR racing
Fruit vs. Vegetable
Banana
Apple
Melon
Grapes
Lemon
Avocado
Orange
Grape fruit
Kiwi
Papaya
Mango
Lime
Tomato
Onion
Carrot
Pepper
Potato
Jalapeno
Cucumber
Bitter Melon
Spinach
Garlic
Ginger
Broccoli
Plantain
Lettuce
Cabbage
Pumpkin
Example:
• Fruits  banana
– Sweet, can eat without cooking, lots of vitamin,
from tropical countries, soft, ripe quickly, easy
to eat, kids love it, tasty, can bring it for hiking
• Vegetables  carrot
– Not sweet, not tasty, require some cooking, lots
of vitamin, from anywhere, hard, stay long,
kids don’t like it, hard
Probabilistic view
• The boundaries of categories are fuzzy
(probabilistically determined).
• Some members are more probable than
others.
• But we are pretty sure about what “dog”
means.
• How do we mentally represent categorical
knowledge?
Organization of categories
• Members of categories are organized in
relation to some focal members.
(prototype)
• Focal members play the role of a “reference
point.”
• The boundaries of categories may be fuzzy,
but people know pretty well which items are
“good/bad” members of a category.
– Penguin vs. robin, chair vs. rug,
Measuring “goodness” of
category members
• Rosch et al. (1975)
• Experiments:
• Subjects were given a list containing the
names of category members.
• Subjects rated (using a 1-10 scale) the
goodness of membership.
– E.g., given “pistol”, subjects rated how good a
pistol is as a member of the category
“weapons.”
• Furniture (chair, lamp, rug, dresser, desk, stove, table, stool,
television, fan, bed, television, counter)
• Fruit (apple, grapefruit, watermelon, banana, cherries,
boysenberry, pear, strawberries, lemon, orange, pineapple,
nut)
• Vehicle (car, airplane, sled, bus, bicycle, wheelchair, truck,
boat, tractor, ambulance, trolley, wagon).
• Weapon (pistol, arrow, slingshot, sword, tomahawk, whip,
knife, cannon, fist, rifle, club, bow)
• Vegetable (peas, celery, mushrooms, corn, turnips, potatoes,
carrots, tomatoes, green onions, green beans, artichoke,
pumpkin)….
• Other categories, bird, sport, toy, clothing.
Results:
– Correlations: 0.95 or up (=1 is perfect correlation)
– People agree very much which items are good/bad examples of a
particular category.
– Categories have “good” examples and “bad” examples.
– The boundaries of categories are graded, and may be arranged
probabilistically with “goodness” of membership.
• What determine “goodness”? Or what makes a particular
item a good example of a category?
Typicality and feature
distribution
• What makes an item a typical member of a
category.
• How do we perceive a particular item a
typical member of a given category?
Family resemblance Rosch &
Mervis (1975)
• Distribution of attributes (features)
– The most typical item in a category has the
most features in common with other members
of a category,
– and the fewest features in common with the
member of contrasting categories.
• These items are ideal examples and may be
referred to as “prototype.”
Which woman looks more
attractive/friendly/pleasant/capable?
Which woman looks more
attractive/friendly/pleasant/capable?
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=
Who is he/she?
12

Morphed images of two different human faces
( Angelina Jolie – Brad Pitt by Na Yung Yu)
1
4
6
9
12
15
19
20
By Na Yung Yu
By me
Just averaging the two faces
Vertical structure of categories
• Why “dog” rather than “animal”?
• Categories have a vertical structure.
• Not all levels of categories are created equal.
– One intermediate level of categories, which is
called, basic level categories, plays a crucial
role in our perceptual and cognitive operations
Rosch et al. (1978)
• Basic (intermediate) level categories
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Most efficient in identification
Evokes specific visual representations
People use this level exclusively for naming
Kids tend to learn these names earlier than
other levels of categories
Exp. 1
• Speed of classification
• Shown a category name (animal -upper
level, dog-intermediate level, or German
shepherd low level) followed by a picture.
• Subjects responded whether the category
name matched with the picture (pressing a
either yes or no key)
Animal
Bear
Polar bear
Results :
Basic level items are the easiest to classify
Response time (ms)
Superordinate Basic level Subordinate
TRUE
591
535
659
FALSE
630
578
642
Rosch et. al (1975)
Basic level categories and
representation
• Basic level categories evoke specific visual
representations.
– Given “furniture”, what kind of representation
do you have in your mind?
– How about “desk”?
• Basic level category names evokes a
specific pictorial representation
Rosh et al. (1978)
• Object matching task and priming
• Object matching task
– Two pictures were shown on a screen briefly
side by side.
– Subjects’ task was to indicate whether or not
the two pictures depicted identical objects
2 conditions
• Primed trials
– 2 seconds before the presentation of picture
pairs, the category name of one of the pair was
presented.
• Non primed trials
– No names were given prior to the trials.
• Dependent measure
– Accuracy and response time
Procedure (primed condition)
Animal / cat / Persian cat
Depending on
trials, upper
(animal), basic
(intermediate), or
low level (Persian
cat) category
names appeared.
Yes/no
• 15 subjects  primed with upper level
names (animal)
• 15 subjects  primed with basic level
names (dog)
• 15 subjects  low level names (German
shepherd)
• All the subjects were also given non-primed
trials.
animal
mammal
cat
kitten
Results:
RT for “Same”
Priming
conditions
Superordinate
(animal)
Basic level
name (cat)
Subordinate
(kitten)
Primed
620
554
568
Unprimed
592
601
612
Difference
-18
47
44
Interpretation
• Given the name of a basic level category,
people form a specific pictorial
representation.
Categories/Concept
• Categories have a structure.
– Horizontal structure
• Distinction between dogs vs. Cats.
• Prototype, family resemblance
– The most typical item in a category has the most features in common
with other members of a category,
– and the fewest features in common with the member of contrasting
categories.
– Vertical structure
• (Animal, mammal, dog, German Shepherd)
• The mid-level categories that we used for naming are called “basic
level” categories.
• Basic level categories have cognitive and perceptual significance.