Cognitive Psychology: Chapter 9

Activation of units in a network therefore depends on two things:

(1) the signal that originates in the input units and (2) the connection weights throughout the network.

Spreading activation

- Activation is the arousal level of a node - When a node is activated, activity spreads out along all connected links - Concepts that receive activation are primed and more easily accessed from memory

Myer and Schvaneveldt: Lexical decision task

- Participants read stimuli and are asked to say as quickly as possible whether the item is a word or not. -The result was that reaction time was faster when the two words were associated.

Exemplars

-Actual members of the category that a person has encountered in the past. Thus, if a person has encountered sparrows, robins, and blue jays in the past, each of these would be an exemplar for the category "birds."

Definitional approach

-Creating definition for categories. -We can decide whether something is a member of a category by determining whether a particular object meets the definition of the category.

Ludwig Wittgenstein: Family Resemblance

-Dealt with the problem that definitions often do not include all members of a category. Family resemblance refers to the idea that things in a particular category resemble one another in a number of ways

Sentence Verification Technique

-Determine how rapidly people could answer questions about an object's category. -They found that subjects responded faster for objects that are high in prototypicality (like apple for the category "fruit") than they did for objects that are low in prototypicality (like pomegranate;)

Exemplar approach to organization

-Determining whether an object is similar to other objects. -explains typicality effect Concept is represented by multiple examples (rather than a single prototype)

Parallel distributed processing (PDP) models

-Propose that concepts are represented by activity that is distributed across a network. -

Rosch: The Prototype Approach

-Rosch (1975b) demonstrated that prototypical members of a category are more affected by a priming stimulus than are nonprototypical members. Subjects first heard the prime, which was the name of a color, such as "green." Two seconds later they saw a pair of colors side by side and indicated, by pressing a key as quickly as possible, whether the two colors were the same or different.

Criticism of Collins and Quillian

1) Cannot explain typicality effects - 2)Cognitive economy-that people may, in fact, store specific properties of concepts (like "has wings" for "canary") right at the node for that concept 3) Some sentence-verification results are problematic for the model

Rosch's Approach: 3 categories?

1) The superordinate level, which we will call the global level (for example, "furniture"); 2) The basic level (for example, "table"); 3) The subordinate level, which we will call the specific level (for example, "kitchen table"). Thus, the level that is "special"—meaning that people tend to focus on it—is not the same for everyone. Generally, people with more expertise and familiarity with a particular category tend to focus on more specific information that Rosch associated with the spe- cific level.

What age do infants begin to form basic levels of categories?

3-4 months

Prototype

A "typical" member of the category. -based on an average of members of a category that are commonly experienced. For example, the prototype for the category "birds" might be based on some of the birds you usually see, such as sparrows, robins, and blue jays, but doesn't necessarily look exactly like any one of them. Thus, the prototype is not an actual member of the category but is an "average" representation of the category

Which term is most closely associated with semantic networks?

Cognitive Economy

One of the key properties of the _______ approach is that a specific concept is reporesented by activity that is distributed over many units in the network

Connectionist

_________ are actual memebers of a catergory that a person has encountered in the past

Exemplars

Connectionist theroy states that a particular object (like a canary) is identified by activity in the specific "canary" output of the network

False

High Typicality

High typicality means that a category member closely resembles the category prototype

Category

Includes all possible examples of a particular concept. Thus, the category "cats" includes tabbies, Siamese cats, Persian cats, wildcats, leopards, and so on.

Which of the following in NOT a property of the connectionist approach

It proposes a slow learning process that eventually creates a network capable of hanling a wide range of inputs.

Hierarchical Organization

Larger, more general categories are divided into smaller, more specific categories, creating a number of levels of categories

Which approach—prototypes or exemplars—provides a better description of how people use categories?

May use both • Exemplars may work best for small categories • Prototypes may work best for larger categories

Prototype Approach to categorization

Membership in a category is determined by comparing the object to a prototype that represents the category.

Protoypical objects are affected more by ________

PRIMING

Naming

People are more likley to list some objects than others when asked to name objects in a category

Priming

Presentation of one stimulus affects responses to a stimilulus that follows

Collins and Quillian: Semantic Network Approach

Proposes that concepts are arranged in networks.

The Connectionist Approach

Proposes that concepts are represented in networks that consist of input units, hidden units, and output units, and that information about concepts is represented in these networks by a distributed activation of these units. -Slow learning process that creates a network capable of handling a wide range of inputs • Knowledge represented in the distributed activity of many units • Weights determine at each connection how strongly an incoming signal will activate the next unit 1 bit can only be on or off - Group them together and get many more patterns (1 byte: 00110011) • Our neurons group together to form a network to represent concepts

What is the difference between prototypes and exemplars? What are the advantages of exemplar categorization over prototype categorization?

Prototypes are believed to be used when we initially learn about a category, along with this prototypes are more used for larger categories of things. Exemplars are believed to be used when we are familiar with a category and used for small categories

Cognitive economy.

Shared properties are only stored at higher-level nodes

Connectionist networks can explain generalization of learning because

Similar concepts have similar patterns, training a system to recognize the properties of one concept (such as "canary") also provides information about other, related concepts (such as "robin" or "sparrow").

The connectionist network has learned the correct pattern for a concept when

The back propagated error singal is zero

Low Typicality

The category member does not closely resemble a typical member of the category. -"Typical" member

Categorization

The process by which things are placed in categories.

Connectionism

an approach to creating computer models for representing cognitive processes.

What are some advantages/disadvantages of both?

both of these have a hard time dealing with typical category (?)

Nodes (Collins and Quillian)

category and concept information is stored. all nodes and concepts are linked. how concepts and properties are associated in the mind

Connection weight

determines how signals sent from one unit either increase or decrease the activity of the next unit. These weights correspond to what happens at a synapse that transmits sig- nals from one neuron to another

Priming occurs when presentation of one stimulus

facilitates the response to another stimulus

Typicality Effect

individuals respond more quickly to typical examples of a category than they would to examples that are considered atypical.

Conceptual Knowledge

knowledge that enables us to recognize objects and events and to make inferences about their properties

Prototype approach to categorization has advantages over the definitional approach, because ____________

not all items within a category are alike

Concepts

the mental representation of a class or individual and "the meaning of objects, events, and abstract ideas"