lecture 8 - concepts and categorisation Flashcards
what is a concept
a mental representation useful for cognitive efficacy
what are the two types of concepts
- logical concepts
- natural concepts
what is categorisation
the process by which things are placed into groups
why do we categorise
- it reduces complexity of the enviro (cognitive economy)
- it allows us to recognise novel patterns
- allows us to establish hierarchy of objects
what is cognitive economy
reducing the complexity of the environment
what did roch provide evidence for in the natural categories
psychological privelage
what are the 3 levels of the natural categories as a hierachy
- global (subordinate)
- basic
- specific (subordinate)
explain the natural category - superordinate level
- highest level of abstraction
- consists of general categories
- consists of only a few attributes
- top level
- eg birds , furniture
explain the subordinate level of the natural category : as a hierachy
- lowest level of abstraction
- consists of specific types of objects
- consists of many attributes
- eg end of table, songsparrow
explain the basic level of the natural category : as a hierachy
- exists between the 2 extremes subordinate and superordinate
- is a balance between informativeness and economy (informativeness- of attributes the concept conveys )(economy - the summary of the important attributes)
- usually acquired first by children
- recognised more quickly by non experts
- eg table, sparrow
who usually aquires basic level hierachys first
usually first acquired by children
provide some evidence that Evidence that Basic-Level Is Special
- people almost exclusively use basic-lecek names in free naming tasks
- quicker to identify basic level category as a member of a category
- children learn basic level quicker than other levels
- basic level is much more common in adult discourse for superordinate categories
- different cultures tend to use the same basic level categories - at least for living things
how does basic level hierachys change within cultures
- different cultures tend to use the same basic level categories - at least for living things
what are the two types of characteristics proposed as occurring within a category
family resemblance
and
typicality
explain family resemblance characteristic
first proposed by Wittgenstein (1953)
is a continuous variable
is a measure of the overlap between members within a category
is measured by the number of shared attributes
how is family resemblance measured
is a measure of the overlap between members within a category
is measured by the number of shared attributes
explain typicality
refers to the differences in how well members relate to their category (e.g., collie vs. dachshund)
the higher the family resemblance the more typical the item is for common taxonomic categories
what happened in rochs experiment
- pps had to rate a list of words / objects
- judged on a scale of 1 (good example of a category ) to 7 (poor example)
rated birds and furniture
explain the The Defining-Attribute View to a concept
Frege (1952) said a concept can be characterized by a set of defining attributes
intension:
the set of attributes that define what it is to be a member of the concept
bachelor - (male, single, adult)
extension:
the set of entities that are members of the concept
bachelor - (every bachelor)
All of the attributes must be present
Assumes categories are clearly defined and rigid
Defining attributes vs. characteristic attributes
what did frege say that the the 2 sets of defining attributes of a concept are
intension:
the set of attributes that define what it is to be a member of the concept
bachelor - (male, single, adult)
extension:
the set of entities that are members of the concept
bachelor - (every bachelor)
exp;lain the Definitional Approach to Categorization
Determine category membership based on whether the object meets the definition of the category
Does not work well
Not all members of everyday categories have the same defining features
does the Definitional Approach to Categorization work
- doesnt work well
- not all members of everyday categories have the same defining features
- eg chairs - can be a sofa, arm chair, bean bag
what is the prototype view
Categorization occurs by finding the best prototype/TBC item match
what are the different types of prototypes
- average of all members
- a specific instance of the category
- a set of characteristic attributes
- regardless, the prototype is the most typical
what is the evidence given for the prototype view
- the typicality gradient is a good predictor of the categorization time
- the most typical member is usually named first
- children learn the typical members first
what is the Typicality effect of the prototype apporoach
- prototypical objects are processed preferentially
- prototypical category members are more effected by a priming stimulus
- roch1975- hearing green primes a highly protoypical green
what is the procedure for rochs prototypical experiment
- priming experiment
what are the result of rochs experiment
Results for the conditions when the test colors were the same are shown on the right. (a) The person’s “green” prototype matches the good green, but (b) is a poor match for the light green.
what is the examplar approach
- concept is represented by multiple examples
(rather than a single prototype) - Examples are actual category members (not abstract averages)
To categorize, compare the new item to stored examples
how is the examplar approach similar to the prototype view
- both say representing a category is not defining it
how does the examplar approach differ to the prototype view
- representation is not abstract
- descriptions of specific examples
- The more similar a specific exemplar is to a known category member, the faster it will be categorized
what does the examplar approach explain
Explains typicality effect
Easily takes into account atypical cases
Easily deals with variable categories
what is a semantic network
Concepts are arranged in networks that represent the way concepts are organized in the mind
what is a node
category/concept
what does collins and Quilian assume about semantic networks
- nodes= concepts/ categories
- concepts are linked
- model for how concepts and properties are associated in the mind
how does cognitive economy explain semantic networks
Cognitive economy: shared properties are only stored at higher-level nodes
Exceptions are stored at lower nodes
Inheritance
Lower-level items share properties of higher-level items
what does the distance between concepts predict
: The distance between concepts predicts how long it takes to retrieve information about concepts as measured by the sentence verification technique. Because it is necessary to travel on two links to get from canary to animal (left), but on only one to get from canary to bird (right) it should take longer to verify the statement “a canary is an animal
explain Spreading activation
of semantic networks
- activation in the arousal level of the 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
what are the criticisms of collins and quillians semantic networks
- cant explain typiclaity effects
- cognitive economy
- some sentance verification results are problematic for the model
what are the strengths and weaknesses of the semantic networks
- Is predictive and explanatory of some results, but not all
- Generated multiple experiments
- Lack of falsifiability
- No rules for determining link length or how long activation will spread
- Therefore, there is no experiment that would “prove it wrong”
- Circular reasoning
what are the 3 types of neuron like units in the connectionist approach
input units : activated activated by stimulation from environment
hidden units: receive input from input units
output units: receive input from hidden units
explain the connectionist approach
Parallel distributed processing
Knowledge represented in the distributed activity of many units
Weights determine at each connection how strongly an incoming signal will activate the next unit
explain how learning occurs in the connectionist approach
How learning occurs
Network responds to stimulus
Provided with correct response
Modifies responding to match correct response
what is error signal in the connectionist approach
- difference between actual activity of each output unit and the correct activity
what is backpropagation the connectionist approach
error signal transmitted back through the circuit
indicates how weights should be changed to allow the output signal to match the correct signal
the process repeats until the error signal is zero
explain how learning occurs in the connectionist approach
Slow learning process that creates a network capable of handling a wide range of inputs
Learning can be generalized
Graceful degradation: disruption of performance occurs gradually as parts of the system are damaged
