THE KNOWLEDGE- BASED VIEW OF

CONCEPTS AND CATEGORIZATION

• People’s knowledge and worldview

• Murphy and Medin- Relationship between concept and examples – analogous to that between theory and supporting data.

• to justify the classification and to explain why certain instances happen to go together

• an apparently disparate collection of objects - a coherent category in particular circumstances.

• Barsalou(1983)-

• Category- children, pets, photo albums, family heirlooms and cash

• a fire is about to engulf a house- “things to save”.

• Goldfish isn’t a particularly prototypic pet or fish. (Hampton,2007;Wu and Barslou,2009)

• Other approaches-fail to answer -how things in the same category go together.

• people’s theories or mental explanations about the world are intertwined with their concepts and provide the basis for categorization. (Heit,1997)

• It allows explaining -1. the instances that go together and why

2. the features and aspects of instances that are important and why

3. the features and aspects that are irrelevant and why

• Medin(1989), based on work by Hilary Putnam(1975)

• examined people’s reliance on underlying nature as a basis of many concepts.

• Psychological essentialism1. objects, people, or events have certain essences • Essence limits the kinds of variation that different instances of a

category can show.

• connect deeper properties to superficial properties.

• Medin (1989)- the categories male and female

• May sometimes make error, but correct most of the time.

• People’s knowledge of the essence of a category varies by level of expertise.

• Biologists, know a lot more about the genetic structure than do laypeople.

• Experts make different and more accurate classification.

• Medin’s (1989) idea is that classifying on the basis of perceptual or other superficial similarity may be effective strategy.

• People classify on the basis of deeper principles.

• People’s classification will change as they become more experience and knowledgeable.

• The way people acquire and mentally represent may also vary as a function of what the concepts are(Murphy,2005).

• Kinds of concepts-1. Nominal kind concepts2. Natural kind concepts3. Artifacts concepts

1.Nominal kind concepts-• have clear definitions.• Include information about necessary and sufficient features.

2.Natural kind concepts-• are things naturally occurring in some environment• Include information about definitional or essential features, especially about

molecular and chromosomal structure.• Have family resemblance structure but equally well explained within a knowledge

based approach.

3.Artifacts concepts-• Things constructed to serve some function or accomplish some task.• Highlight information about the object’s purpose or function and may be

adequately described only within the knowledge based approach.

• Barton and Komatsu (1989)-

• Presented participants with five natural kind concepts (goat, water, gold).

• Five artifacts (tv, pencil, mirror).

• Asked to imagine transformation- some were phrased in terms of function or purpose others were in terms of physical features and third type in change was molecular.

• Result- In natural kind Ps were most sensitive to molecular transformations and In artifacts most sensitive to functional changes.

• All concepts are not treated equally.

Five approaches to conceptual structure categorized into 2 major types

Similarity based category

Classical , prototype &

exemplar views

Categorization based on the similarity of an

instance abstract specification of the

category or to one or more exemplars.

Explanation based category

(Komatsu,1992)Schemata/ scripts

view & some knowledge based

view

Classification based on the meaningful

relationships among instances and categories.

Goodman term similarity is pretty empty without some specification of what the relevant respects are.

The contrast between similarity-based and explanation-based approach :

Degree to which people focus on superficial, perceptual information about a particular object

Versus

Degree to which they focus on deeper, knowledge – derived information about an objects function or role.

The five approaches to concepts differ on several dimensions.

Cognitive economy of the mental representation• Idea is to save on mental resources by limiting the amount of information we must

store.

Informativeness of the category.

So, any theory of concepts and categorization must STRIKE A BALANCE between cognitive economy and informativeness.

Any theory of concepts must explain a concept or category’s coherence.

Workers in artificial intelligence – discovering – that a truly intelligent program or system must have• a wide or deep knowledge base and • must be able not only to store but also retrieve a great deal of information

to the world.

Proponents of knowledge based view of concepts hold that people use their own theories to guide their classification of objects.

Experts have more elaborated theories and therefore different mental representation than do novices.

Organizing knowledge

Network Models ACT Models Connectionis

t Models

Forming Concepts and Categorizing New Instances

The Classical View

The Prototype

View

The Exemplar

View

The Schemata / Scripts View

The Knowledge-Based View

THANK YOU!