what is a concept?
DESCRIPTION
What is a concept?. Part of semantic memory (vs. episodic memory) A class of items that seem to belong together ‘dog’, ‘balloon’, ‘terrorist’ (things) ‘tall’, ‘ugly’ (properties) ‘walk’, ‘jump’ (actions) A mental construct (vs. the outside world) Abstract knowledge . - PowerPoint PPT PresentationTRANSCRIPT
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What is a concept?
• Part of semantic memory (vs. episodic memory)• A class of items that seem to belong together
– ‘dog’, ‘balloon’, ‘terrorist’ (things) – ‘tall’, ‘ugly’ (properties) – ‘walk’, ‘jump’ (actions)
• A mental construct (vs. the outside world)• Abstract knowledge
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• How are things clustered into categories?
• Based on similarity big birdn sesame jump)t
Sesamestreet_bigbird
Sesametstree_jump
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German Shepherd
fidoprince puppy
formerly known as prince
bingojessie
- Abstract representation
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What does it mean to know what a ‘dog’ is?
• Classical View:– To know what a ‘dog’ is, is to know its definition.– Dog = mammal, four legs, barks, wags tail – These properties are
• Singly necessary: every member must have them• Jointly sufficient: everything that have them is a member
– Categories have sharp boundaries • Either you are in or you are out
– Categories have a homogeneous space• Everyone that is ‘in’ is equally good member of the category
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Classical View: Problems• Good definitions are hard to find! • Example: A bachelor is an unmarried man
– is my kid a bachelor? Adult – is the pope a bachelor? intention to get married
• Some members are more typical than others (Categories have internal structure) – Basketball, golf, mini-golf– Cup, tea cup, stanley cup, C-cup
Solution:– There are no defining properties, but rather– properties characteristic of the group (typical features)
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Birdie birdBird?
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• Is Pluto a planet or a ‘dwarf planet’? Npr(silly question)
Mother:- ‘working’ mother- ‘adoptive’ mother
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• A prototype:– is an abstract representation (usually the average)– contains salient features that are true of most instances
e.g., birds usually can fly (but not always) =>
‘ability to fly’ is a salient feature of the category ‘bird’A prototypical bird is one that flies (& have feathers, etc)A bird that doesn’t fly is atypical (weird: penguin, ostrich)
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• Prototype Theory (Rosch)– specify the “center” of the category, – leave ‘fuzzy’ boundaries – graded category membership (tea cup vs. Stanley cup)
• some categories don’t obey these properties– Things that have ‘essence’ (‘human’ ‘marriage’)??
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Prototypes and Basic Level
• Physical Object• Living Thing• Animal• Mammal• Carnivore• Canine• Dog• Australian Shepherd
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Superordinate
BASIC
things
Vehicle Furniture Animal
Truck
Pickup Truck
Chair
Kitchen Chair
Fish
Trout
Subordinate
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Living Thing
Animal Plant
Fish Bird
Trout Salmon
Superordinate: Low similarity within category (low coherence) Animals look different from each other
BASIC level:-High similarity within category All fish look the same
-Low similarity between categoriesFishes look different from other animals
Subordinate: High similarity between categories (low discriminability)Different types of fish look similar to each other
Except to Experts
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• Properties of the Basic Level Categories– Maximize within-category similarity– Minimize between- Category similarity– Maximum level of abstraction while
maintaining physical similarity– Shorter name
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Basic Level
• “There is generally one level of abstraction at which the most basic category cuts can be made. ..
• …the basic level of abstraction in a taxonomy is the level at which categories carry the most information.” Rosch et al. 1976)
• One privileged level
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Why are concepts useful? Functions• Coding of experience: Classification of items as members of the
same category
– Reduces cognitive demands – Facilitates communication – Inductive Inferences
• Natural kinds vs. artifacts – Combines to create complex categories
• Contact lens• Digital Camera
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Concepts and Misconceptions
• Stereotypes (social categories)– Blacks, Republicans, Arab Nations– Stereotypes reduce complexity– The reduction in complexity leads to errors
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• Extreme examples of the category are more heavily weighted – same is true for some other categories, e.g. trees
• Within-category variability is underestimated– “all Bush supporters are the same”
• Insensitivity to disconfirmation– Members who challenge the stereotype are thought to be ‘special cases’ (poor examples of the
category). Therefore – they are thought not to be diagnostic of the category.– “No women is a good soldier. A good female soldier, is less of a woman”
• Stereotypes are more stable than is warranted by evidence – test-retest reliability: after one week .94 after 4 years .92
• Illusory correlation– Distinctive behavior - Distinctive individuals are perceived to ‘go together’ even when they are
independent (e.g., antisocial behavior - blacks)• Misattribution (race – poverty – education- neighborhood)
• Racial stereotypes are thought as ‘essential’ categories
Stereotypical biases