conceptual knowledge
knowledge that enables us to recognize objects and events and to make inferences about their properties
category
includes all possible examples of a particular concept.
concepts
“the mental representation of a class or individual” or “the meaning of objects, events, and abstract ideas”
categorisation
the process by which things are placed in categories.
definitional approach to categorisations
we can decide whether something is a member of a category by determining whether a particular object meets the definition of the category
- Definitions work well for geometric objects but not really well for natural objects –> - not all of the members of everyday categories have the same features
family resemblance Ludwig Wittgenstein
things in a particular category resemble one another in a number of ways. (deals with problem that definitions often do not include all members of a category)
approach allows for some variation within a category
prototype approach to categorisation
eleanor rosch
membership in a category is determined by comparing the object to a prototype that represents the category.
prototype
“typical” member of the category. (based on an average of members of a category that are commonly experienced) average” representation of the category
high typicality
closely resembles the category prototype (it is like a “typical” member of the category).
low typicality
the category member does not closely resemble a typical member of the category.
prototype experiment
Rosch and Mervis experiment
- Participants assigned many of the same characteristics to chair and sofa.
- eg. chairs and sofas share the characteristics of having legs, having backs, you sit on them, they can have cushions, and so on.
- When an item’s characteristics have a large amount of overlap with the characteristics of many other items in a category= high family resemblance.
- relationship between family resemblance and prototypicality.
- good examples of the category “furniture,” such as chair and sofa, share many attributes with other members of this category; poor examples, like mirror and telephone, do not.
sentence verification technique
edward smith
determine how rapidly people could answer questions about an object’s category.
- responded faster for objects with higher prototypicality (fruit) than lower prototypicality (pomegranate)
- typicality effect.
- Subjects tend to list the most prototypical members of the category first
- priming
typicality effect
This ability to judge highly prototypical objects more rapidly is called the typicality effect
priming
when presentation of one stimulus facilitates the response to another stimulus that usually follows closely in time
priming case study
- Rosch (1975b) demonstrated that prototypical members of a category are more affected by a priming stimulus than are nonprototypical members.
- Subjects first heard the colour green (primer)
- Two seconds later they saw a pair of colours side by side and indicated, by pressing a key as quickly as possible, whether the two colours were the same or different.
- paired in three different ways:
(1) colours were the same and were good examples of the category (primary reds, blues, greens, etc.;
(2) colours were the same but were poor examples of the category (less rich versions of the good colours, such as light blue, light green, etc.;
(3) colours were different, with the two colours coming from different categories (red with blue). - The most important result occurred for the two “same” groups.
- In this condition, priming resulted in faster “same” judgments for the prototypical (good) colors (reaction time, RT = 610 ms) than for the nonprototypical (poor) colors (RT = 780 ms).
- Thus, when subjects heard the word green, they judged two patches of primary green as being the same more rapidly than two patches of light green.
- When subjects hear the word green, they imagine a “good” (highly prototypical) green
- Thus, the results of the priming experiments support the idea that subjects create images of prototypes in response to colour names.
the exemplar approach
involves determining whether an object is similar to other objects
the standard for the exemplar approach involves many examples
Exemplars= actual members of the category that a person has encountered in the past (i.e examples)
- explains the typicality effect (in which reaction times on the sentence verification task are faster for better examples of a category than for poorer examples) by proposing that objects that are like more of the exemplars are classified faster.
- Exemplars could explain how we still manage to categorise very
untypical members of a category
- use prototype as we start learning about new categories than use exemplar as we get more specific thus prototype for large categories and exemplar for smaller categories
hierarchical organisation
larger, more general categories are divided into smaller, more specific categories, creating a number of levels of categories
the Rosch and coworkers’ (1976) experiment
- list as many features as you can that would be common to all or most of the objects in the category. For example, for “table” you might list “has legs.”
1. furniture 2. table 3. kitchen table - listed only a few features that were common to all furniture, but many features that were shared by all tables and by all kitchen tables.
- Rosch’s subjects listed an average of 3 common features for the global level category “furniture,” 9 for basic level categories such as “table,” and 10.3 for specific level categories such as “kitchen table”
- going (to global) results in a large loss of information (9 features at the basic vs. 3 at the global level) and going below it (to specific) results in little gain of information)
rosch’s approach: basic level categories
the superordinate level ( global level furniture)
the basic level ( “table”)
subordinate level, which we will call the specific level ( “kitchen table”).
the Rosch and coworkers’ (1976) experiment
basic level categories
list as many features as you can that would be common to all or most of the objects in the category. For example, for “table” you might list “has legs.”
- furniture 2. table 3.kitchen table
3- common features for the global level category “furniture,”
9 - common features for basic level categories such as “table,”
10.3- for specific level categories such as “kitchen table”
-going (to global) results in a large loss of information (9 features at the basic vs. 3 at the global level) and going below it (to specific) results in little gain of information)
How knowledge can affect categorisation
James Tanaka and Marjorie Taylor (1991)
bird watchers
- asked bird experts and nonexperts to name pictures of objects. There were objects from many different categories (tools, clothing, flowers, etc.),
- experts responded by specifying the birds’ species (robin, sparrow, jay, or cardinal), but the nonexperts responded by saying “bird.”
- experts had learned to pay attention to features of birds that nonexperts were unaware of.
- consider not only the properties of the objects but also the learning and experience of the people perceiving those objects
- Thus, the level that is “special”—meaning that people tend to focus on it—is not the same for everyone.
semantic network approach
Proposes that concepts are arranged in networks, where links connecting the concepts indicate that they are related to one another
collins and quillian’s hierarchical model (general concepts are at the top and specific ones at the bottom)
- first semantic network models
- develop a computer model of human memory.
- network consists of nodes that are connected by links
- Each node represents a category or concept, and concepts are placed in the network so that related concepts are connected.
cognitive economy
Related the semantic network approach, involves storing a property about a concept at a higher level that applies to a number of concepts in the same category.
problem-because not all birds fly. (Collins and Quillian added exceptions at lower nodes.
spreading activation
- activity that spreads out along any link that is connected to an activated node.
- according to the idea of spreading activation, this activation also spreads to other nodes in the network, as indicated by the dashed lines.
what is the result of spreading activation
Additional concepts linked to an activated node become primed and can therefore be retrieved more easily from memory.
