1. Mental Categories Def: Two or more perceptually distinct objects are classified as being the same thing (in some relevant way). Cognitive Benefits of CATEGORY formation Greatly reduces learning and memory requirements. Enables us to efficiently order and relate objects and events. Provides probability-based information Allows for quicker decisions about most appropriate way to act in novel situations Allows us to make assumptions about missing details But, assumptions can be wrong, especially when dealing with atypical members of categories.

2. How does the brain represent categories and members of categories? Rigid Definitions Satisfy both Necessary and Sufficient conditions Necessary: In order to be member of Category X, an object must have Feature X Sufficient: If an object has Feature X, then it must be a member of Category X Q: Does the human mind represent categories in terms of rigid definitions? A: No, at least for most things.

3. Prototype Theory Rosch (1973) Instead of asking “is Object A a member of category X?” We should ask “is Object A a typical member of category X?” What is a Prototype? Idea goes back to Plato (platonic ideal). Is it an average (mean)? Kind of, but not really. Is it the most common (mode)? Kind of, but not really. Prototypes tend to be more complex and more abstract than what is derived from a simple statistical mean or mode.

4. Wittgenstein (1953): Family Resemblance Objects and ideas cluster together on the basis of shared features A category is a flexible, approximate boundary that forms around clusters of objects that share features on some relevant dimension In some cases, objects can be members of the same category without directly sharing any features Object A shares Feature X with Object B Object B shares Feature Y with Object C Object A and Object C are related to each other via Object B Rosch (1973): Continuous Dimensions and Overlapping Boundaries Prototype: The most typical member of a category Shares the most features with members of its own category Shares the fewest features with members of other categories

5. Category A Category B The Prototype

6. Name an instance of X: The most frequent answers (in order) for two categories. Fruit: Apple Peach Pear Grape Strawberry Blueberry Lemon Watermelon Raisin Fig Pomegranate Coconut Avocado Pumpkin Olive Bird: Robin Bluebird Seagull Swallow Falcon Mockingbird Starling Owl Vulture Sandpiper Chicken Flamingo Albatross Penguin Bat

7. Resemblance Theories: Prototype vs. ExemplarThe Standard = The acting representative of the category The “standard” prototype The “standard” exemplar An exemplar is a concrete representation. A specific instance that happens to be the most active in memory. More typical members tend to be the most active, on average. A prototype is an abstract representation that is derived from the “center of mass” of the features of all the objects in the category.

8. Prototype vs. Exemplar Theory:Contrasting Predictions What happens when the most common member of a category is not the most typical member? Prototype and Exemplar theories make different predictions about how the standard will be formed in this case Prototype: Most Typical >> Most Common Exemplar: Most Common>> Most Typical Furthermore In Exemplar theory, the standard can vary from time to time. In Prototype theory, the standard can be something that doesn’t actually exist.

9. The TAVE non-word experiment Most people pronounce the non-word TAVE like the words SAVE and CAVE, not like HAVE There are hundreds of -AVE words pronounced like SAVE There is only one -AVE word pronounced as HAVE However, HAVE is by far the most common -AVE word It occurs thousands of times more often then all the others put together Exemplar theory predicts TAVE = HAVE The data suggest otherwise However, TAVE = HAVE was occasionally observed (about 10%) Pronunciation was found to be influenced by priming effects These caveats are problematic for Prototype theory

10. Parallel Prototype/Exemplar System The standard is formed through combined prototype and exemplar mechanisms prototype standard exemplar standard