Chapter 9: Knowledge
units
"Neuronlike processing units" in a connectionist network.
cognitive economy
A feature of some semantic network models in which properties of a category that are shared by many members of a category are stores at a higher-level node in the network.
concepts
A mental representation of a class or individual. Also, the meaning of objects, events, and abstract ideas. An example of a concept would be the way a person mentally represents cat or house.
hub and spoke model
A model of semantic knowledge that proposes that areas of the brain that are associated with different functions are connected to the anterior temporal lobe, which integrates information from these areas.
connectionism
A network model of mental operation that proposes that concepts are represented in networks that are modelled after neural networks. This approach to describing the mental representation of concepts is also called the parallel distributed processing (PDP) approach.
lexical decision task
A procedure in which a person is asked to decide as quickly as possible whether a particular stimulus is a word or a nonword.
transcranial magnetic stimulation (TMS)
A procedure in which magnetic pulses are applied to the skull in order to temporarily disrupt the functioning of part of the brain.
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.
category-specific memory impairment
A result of brain damage in which the patient has trouble recognising objects in a specific category.
prototype
A standard used in categorisation that is formed by averaging the category members a person has encountered in the past.
sentence verification technique
A technique in which the participant is asked to indicate whether a particular sentence is true or false. For example, sentences like "an apple is a fruit" have been used in studies on categorisation.
spreading activation
Activity that spreads out along any link in a semantic network that is connected to an activated node.
semantic category approach
An approach to describing how semantic information is represented in the brain that proposes that there are specific neural circuits for some specific categories.
semantic network approach
An approach to understanding how concepts are organised in the mind that proposes that concepts are arranged in networks.
crowding
Animals tend to share many properties, such as eyes, eggs, and the ability to move. This is relevant to the multiple-factor approach to the representation of concepts in the brain.
anterior temporal lobe (ATL)
Area in the temporal lobe. Damage to the ATL has been connected with semantic deficits in dementia patients and with the savant syndrome.
hierarchical model
As applied to knowledge representation, a model that consists of levels arranged so that more specific concepts, such as canary or salmon, are the bottom and more general concepts, such as bird, fish, or animal, are at higher levels.
semantic dementia
Condition in which there is a general loss of knowledge for all concepts
semantic somatotopy
Correspondence between words related to specific parts of the body and the location of brain activity associated with the part of the body.
graceful degredation
Disruption of performance due to damage to a system that occurs only gradually as parts of the system are damaged. This occurs in some cases of brain damage and also when parts of a connectionist network are damaged.
error signal
During learning in a connectionist network, the difference between the output signal generated by particular stimulus and the output that actually represents that stimulus.
sensory-functional hypothesis
Explanation of how semantic information is represented in the brain that states that the ability to differentiate living things and artefacts depends on one system that distinguishes sensory attributes and another system that distinguishes function.
category
Groups of objects that belong together because they belong to the same class of objects.
specific level
In Rosch's categorisation scheme, the level below the basic level.
basic level
In Rosch's categorisation scheme, the level below the global (superordinate) level. According to Rosch, the basic level is psychologically special because it is the level above which much information is lost and below little is gained.
exemplars
In categorization, members of a category that a person has experienced in the past.
connection weight
In connectionist models, a connection weight determines the degree to which signals sent from one unit either increase or decrease the activity of the next unit.
family resemblance
In considering the process of categorisation, the idea that things in a particular category resemble each other in a number of ways. This approach can be contrasted with the definitional approach, which states that an object belongs to a category only when it meets a definite set of criteria.
concept
Knowledge that enables people to recognise objects and events and to make inferences about their properties.
conceptual knowledge
Knowledge that enables people to recognise objects and events and to make inferences about their properties.
Unit (in a connectionist network)
Neuronlike processing units in a connectionist network.
mirror neurons
Neurons in the premotor cortex originally discovered in the monkey, that respond both when a monkey observes someone else carrying out an action and when the monkey itself carries out the action. There is also evidence for mirror neurons in humans.
hierarchical organization
Organisation of categories in which larger, more general categories are divided into smaller, more specific categories. These smaller categories can, in turn, be divided into even more specific categories to create a number of levels.
embodied approach
Proposal that our knowledge of concepts is based on reactivation of sensory and motor processes that occur when we interact with an object.
multiple-factor approach
Seeking to describe how concepts are represented in the brain by searching for multiple factors that determine how concepts are divided up within a category.
typicality effect
The ability to judge the truth or falsity of sentences involving high-prototypical members of a category more rapidly than sentences involving low-prototypical members of a category.
exemplar
The approach to categorisation in which members of a category are judged against exemplars--examples of members of the category that the person has encountered in the past.
exemplar approach to categorisation
The approach to categorisation in which members of a category are judged against exemplars--examples of members of the category that the person has encountered in the past.
global level
The highest level in Rosch's categorisation scheme.
definitional approach to categorisation
The idea that we can decide whether something is a member of a category by determining whether the object meets the definition of the category.
prototype approach to categorisation
The idea that we decide whether something is a member of a category by determining whether it is similar to a standard representation of the category, called a prototype.
superordinate (global) level
The most general category level distinguished by Rosch
superordinate level
The most general category level distinguished by Rosch.
subordinate (specific) level
The most specific category level distinguished by Rosch
subordinate level
The most specific category level distinguished by Rosch
categorization
The process by which objects are places in categories.
connectionist network
The type of network proposed by the connectionist approach to the representation of concepts. Connectionist networks are based on neural networks but are not necessarily identical to them. One of the key properties of a connectionist network is that a specific category is represented by activity that is distributed over many units in the network. This contrasts with semantic networks, in which specific categories are represented at individual nodes.
input units
Unites ina connectionist network that are activated by stimulation from the environment.
hidden units
Units in a connectionist network that are located between input units and output units.
output units
Units in a connectionist network that contain the final output of the network.
parallel distributed processing (PDP)
see Connectionism; see also Connectionist network