Cog Psych Chapter 9

Prototype

"typical" member of the category: an averaged out member

Cognitive economy

A feature in some semantic network models in which propertied of a category that are shared by many members of a category are stored at a higher level node in the network. When there are exceptions to these generic features that are placed at a higher level node, the exception characteristic is added at lower nodes

Hierarchical Organization

A level of categories is created by dividing larger, general categories into smaller ones

Back Propagation

A process by which learning can occur in a connectionist network, in which an error signal is transmitted backward through the network. This backward-transmitted error signal provides the information needed to adjust the weights in the network to achieve the correct output signal for a stimulus.

Graceful Degradation

Damage to the system does not completely disrupt its operation because the information is distributed through the network across many units Similar to actual brain damage

Describe the definitional approach to categories. Why does it initially seem like a good way of thinking about categories, but then becomes troublesome when we consider the kinds of objects that can make up a category?

Definitional approach is an all or nothing approach that categorizes objects based on a specific set of features and characteristics. This becomes a problem because there is variation in categories and some objects of the category can be more like the typical representation than others.

What is the exemplar approach? How does it differ from the prototype approach and how might they work together

Exemplar approach compares the object under speculation to all of the exemplars within the category, rather than comparing to just one aggregated item like the prototype approach.

Family Resemblance

Idea proposed by Wittgenstein that refers to the idea that things in a particular category resemble one another in many ways. Allows variation in categories

Connectionist Network

Incoming stimuli activate input units and signals travel through the network, activating hidden and output units. Activity depends on initial activity of the input and how strongly a unit will be activated by incoming activity

What does it mean to say that there are different levels within a category? What arguments did Rosch present to support the idea that one of these levels is "privileged"? How has research on categorization by experts led to modifications of Rosch's ideas about which category is basic or privileged?

Levels: superordinate(general), basic, and subordinate(specific). Rosch said that basic levels are psychologically privileged because going to the level above loses too much information about the object and going a level down barely gains information. Further studies show that levels of categories depends on individual expertise, subordinate levels to the gen pop are basic levels to experts.

Prototype approach to categorization

Membership in category is determined by comparing the object to the prototype that represents the category Problem arose through typicality effect because since membership is based on an average, objects should have the same response time

Exemplar approach to categorization

Membership is determined by comparing the object to all of the exemplars in the category Explains the typicality effect because objects that are more typical, or more like the exemplars are identified faster. A birdier bird is identified as a bird faster than a non birdy bird

Subordinate Level = specific level

Most specific level; almost all of the features are shared between objects in the category

Sentence Verification Technique

Procedure that determines how rapidly people answer questions about an object's category: Subjects respond faster to objects that are more "typical" to the category

How are the properties of various objects filed away in the mind?

Properties of various objects are thought to be filed away in a network, possibly semantic or connectionist

What is the prototype approach? What experiments did Rosch do that demonstrated connections between prototypicality and behavior?

Prototype approach is basing membership off of a comparison to an averaged member, or prototype. In Rosch's experiment, subjects were asked to write down characteristics for each item on a list. Items that were similar shared many characteristics and were seen to have high family resemblance. Because of this, subjects respond faster to objects that are more prototypical.

Why is it difficult to decide if a particular object belongs to a particular category, such as a chair, by looking up its definition?

The definitional approach is extremely limiting due to its specificity in features, so it could be difficult to place a particular object based on its definition because it could barely miss the definition of a category.

Basic level

The most psychologically privileged category. More specific than the general category so it shares more features with the other objects inside of the category

output units

Units in a connectionist network that contain the final output of the network.

Why is the use of categories so important for our day to day functioning?

We use categories in nearly everything. It is a great way to store information and allows quick retrieval.

Rosch's priming experiment

When subjects are primed with a color, they are more likely to respond quicker that the images are the same color if the color of the images is a good example of the color that they were primed with

Concepts

a representation of a class or individual

Typicality effect

ability to judge highly typical objects more rapidly

Spreading Activation

activity that spreads out along any link that is connected to an activated node ex: when one node is activated, moving from robin to bird, any link that is connected to bird is activated and made more accessible for retrieval. The nodes at the end of the links are primed to be accessible for retrieval

Hidden units

acts as a relay between input and output units

Exemplar

actual member of the category that the subject has encountered in the past

Connectionism

approach to creating computer models for representing cognitive processes

Error Signal

caused by erroneous responses in the property units, which leads to the learning process of adjusting weights for proper activation

Semantic Network Approach

concepts are arranged in networds

Parallel distributed processing

connectionist models that propose that concepts are represented by activity that is distributed across a network

Definitional approach to categorization

decide whether something is a part of a category based on an all or nothing list of features. Object must meet specific definition of the category

Activation of units

depends on the initial signal from the input units as well as the connection weights throughout the network.

Connection Weight

determines how signals sent from one unit either increase or decrease the activity of the next unit

Superordinate level = global level

general category so that less features are shared to incorporate more into the category

Category

includes all possible examples of a concept ex: concept: stringed instrument category includes: violins, violas, cellos, bass, guitars, etc

conceptual knowledge

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

Categorization

process by which things are placed in categories

Input units

units activated by stimuli from the environment