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

• How are things clustered into categories?

• Based on similarity big birdn sesame jump)t

• Based on function• Based on theories

Sesamestreet_bigbird

Sesametstree_jump

German Shepherd

fidoprince

puppy formerly known as prince

bingo

jessie

- Abstract representation- salient features- prototype

• 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)

How can we test the existence of a ‘prototype’? Use stimuli that you have never seen before (CogLab exp)

Prototype: Only shown during test phase

Variants:departures from the PrototypeTheir average is the prototypeSome displayed at study and test, others only at test

Training Phase

Abstraction

Prototype (not shown)

Variants

Test Phase

Prototype

Old Variants New Variants

Critical comparison: ?

Prototype theory

• ‘On the genesis of abstract ideas’ (Posner & Keele, 1968)

• Stimulus– Two displays of 25 dots each (Prototypes)– Variants on each of these two displays (10 dots are randomly

relocated)

• Training Phase:– Learn to classify variants into two categories

– Items were variants of the prototypes

• Test phase – Old items

– New Items

• Prototypes

• Variants

• 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’ (next Monday)– Phonemes (CogLab exp)

• Is Pluto a planet? npr

• Or is it a dwarf planet?

• Is this an important question?

• Or is it as dumb question?– (hint: dumb)