Chapter 7: Concepts and Categorization

Category

A class of similar things (objects or entities) that share one of two things: etiehr an essential core (ex: why all sceince courses are called science), or some similarity in perceptual, biological, or functional properties.

Theories of Concept Development

-The classical view
-the prototype view
-the exemplar view
-the schemata view
-the knowledge based view

Classical view

all examples or instances of a concept share a fundamental characteristics or features. Features are individually necessary meaning each example must have the feature to be regarded as a member. A set of features also must be collectively sufficient meaning each feature in the set is automatically an instance of a concept. The goodness of fit of an object in a category was shown to have participants respond faster when asked to answer T/F about a statement like "a chicken is a bird".

Limitations of Classical view

- assumes concepts mentally represent lists of features. Concepts are not representations of specific examples but rather abstractions containing information about properties and characteristics that all examples must have.
- membership is clear-cut. either something has all the necessary and sufficient features or doesn't.

The prototype view

denies the existence of necessary and sufficient feature lists, instead regarding concepts as a different sort of abstraction. Prototypes of concepts include features or aspects that are characteristic of members of the category rather than necessary and sufficient. no individual feature or aspect need to be present in the instance but the more characteristic features of the group it has, the more likely it is to be regarded as a member of the category.

typicality effect

ability to judge highly prototypical objects more rapidly

Limitations of the prototype view

-Variable categories: Hard time explaining why something should or shouldnt be considered a boundary. It doesn't have clear boundaries like the classical view.
-Typicality and context: typicality depends on context. It is not fixed. This contrasts the idea that a member has a certain level of typicality.

Concept

a mental representation that summarizes and organizes information about a category of objects, events, or ideas.

Exemplar view

Concepts are composed of previous instances. Categorization occurs by comparing current instances with previous instances stored in memory. It explains peoples inability to state. necessary and defining features. Also explains why people have difficulty categorizing unclear atypical instances. Also explains why people are more likely to identify typical instances.

Experiment that demonstrated exemplar view (Allen and Brooks)

Demonstrated how specific prior examples can influence categorization over and above the use of simple defining features. Participants were trained with a series of fictional creatures called builders and diggers. Participants were also given a verbal rule that could be used to classify them. Experimenters presented slightly different from to those during training. Specifically, they presented stimuli that were positive match or negative match. The positive match were categorically and visually similar to training. The negative match categorically matched the builder but looked like a digger. Participants took longer to classify and made more errors classifying the negative matches. This was interpreted as participants tended to categorize based on previous exemplars more than simple rules.

Limitations of exemplar view

-Unconstrained like the prototype view.
-Doesn't explain how different exemplars are called to mind.
-exemplar model has difficulty accommodating data from large and complex categories.

Schemata view

concepts are schemas, or organized framework for representing knowledge. Schema can have sub-schemata and/or superschemata. The notion of schemata as underlying organizational units of memory.

Limitations of schemata view

-does not specify clear boundaries among individual schemata.
-not sufficiently defined to be empirically testable.

Knowledge based view

a person classifying objects and events doesn't just compare features or physical aspects of the objects and events to features or aspects of stored representations. Instead a person uses their knowledge of how a concept is organized to justify the classification and to explain why certain instances happen to go together in the same category. This can explain why some instances some odd combinations of objects get grouped together. This answers the question of why that the previous views don't - related to context.

Strategies for Forming new concepts

-simultaneous scanning
-successive scanning
-conservative focusing

Which strategy is most effective?

it depends on the task conditions. If the task did not have cards laid out, those using scanning strategies had more trouble then those who could lay cards out to refer to.
It also depended on whether cards were in an order or not.
An experiment suggests that conservative focusing was superior.

simultaneous scanning

participants figured out ahead of time which card was relevant and to consider carefully how to eliminate the maximum number of hypotheses by choosing the optimal card at each point in the process.

Limitations of simultaneous scanning

- high demands on working memory

successive scanning

a participant tested one hypothesis at a time. For example starting by seeing if the ideal card was black, then seeing the suit as opposed to multiple hypotheses at once like simultaneous scanning.

Limitations of successive scanning

less efficient than simultaneous scanning but is more cognitively manageable.

Conservative focusing

find a card that illustrated the concept (the focus card) then choosing to test other cards that varied from it in only one aspect. This is efficient and relatively easy.

Limitations of conservative focussing

unless cards are laid out in an orderly fashion, it can be difficult to carry out.

Acquiring prototypes

The way people form and learn concepts depends critically on the instances and the categories they must work with.

Acquiring prototypes in the brain

Participants were shown figures with different patterns of 2 different coloured squares from two different artists. They were given several exemplars that were meant to be quite similar. Participants were asked to identify the artist and then given feedback after each trial. brain activation was shown in the frontal and parietal regions of the right hemisphere during early trials. Early trials involved processing of visual patterns and stimuli without application of rules. As learning progressed, the left hemisphere was used. This is presumed to be because more rules are being utilized.

Implicit Concept Learning

when complex underlying structures (like grammar) exist, people are better off using exemplars to learn rather than structure. This is implicit learning as it is not conscious.

How do people decide which strategy to use?

1) task requirement: in natural situations different items in the same category sometimes are treated differently.
2) original learning situation: Most information is not presented in rapid succession rather is occurs repeatedly allowing people to understand certain instances really well.
3) some stimuli lend themselves to hypothesis testing better than others.
4) in real life, instances may belong to multiple categories at the same time.
5) in natural settings we learn about instances without knowing how we will be called on to use them later on.

Do we learn analytically or nonanalytically?

Typically non-analylstically but we use both.

Nominal kind concepts

concepts that have clear definitions
-have sufficient features

Natural kind concepts

are things naturally occurring in some environment
- highlight info about objects function, or knowledge based approach

artifact concepts

things constructed to serve some function or accomplish some task
-objects purpose or function