Chapter 9: Concepts & Knowledge Flashcards
Schematic knowledge
our general knowledge about something in the world that we gain through experience
key components of knowledge
- There is regularity in the way different people organize knowledge and we use this to make inferences
- Much of our knowledge is implicit
- All knowledge is interconnected
- Knowledge depends on semantic memory
semantic knowledge
includes facts we know about the world and ourselves
category
a group of items that are grouped together because they are similar in some way
exemplars
individual members of a category
concept
a mental representation of a category
Medin on concepts
concepts depend on the structure of the world and how we assign meaning to it
Commonsense knowledge problem
a problem in classical AI in which computers don’t possess the same commonsense knowledge as humans because knowledge has to be explicit in classical AI compared to humans’ ability to infer implicit knowledge
classical approach to categorization
- Categories are defined by sets of defining features
- Categorization is a matter of considering defining features of individual exemplars
- Categories are all-or-none
defining features
a feature that is both necessary and sufficient for category membership according to the classical approach
evidence against the classical approach to categorization
- It’s nearly impossible to identify defining category features for most categories
- People recognize that some exemplars are better category members than others
Wittgenstein on the classical appraoch to categorization
Concepts are not based on defining features, but rather are defined by the resemblance to a collection of features.An item can be categorized into more than one category
Rosch, 1975 typicality experiment
asked participants to rate items based on how good of an example of a category an item was. She found that participants could easily give typicality ratings and they agreed with them.
typicality ratings
an experiment in which participants rate how good an exemplar is of a category
typicality effects
experimental effects in which participants behave differently toward typical category members than atypical members, suggesting that typical items have a privileged place in that category
lexical decision task
an experiment task in which participants must decide whether a string of letters is a word or non-word as fast as possible
semantic priming
the observation that a response is facilitated if it is preceded by a semantically relevant stimulus
examples of typicality effects
- we name typical category members before atypical ones
- we are faster to put typical members into categories than atypical ones
- typical exemplars show larger priming effects than atypical ones
- infants learn typical category members first
- when producing sentences, we list typical category members before atypical ones
are typicality effects exclusive to knowledge tasks?
no, typicality effects are also present in sentence production and other cognitive tasks
who proposed the prototype theory of categorization?
Eleanor Rosch
prototype theory of categorization
Proposes that we consider which features are most likely among category members
characteristic features
a feature that category members likely possess but is not required for category membership
prototype
a mental average of all category members; the most typical example of a category member
do prototypes have to exist in reality?
no
what constitutes a typical category member according to the prototype theory?
The more similar something is to a prototype the more typical a category member it is
family ressemblance
the proposal that all category members can belong to a category without all sharing a single common feature. What is needed for category membership is for each category member to share a feature with at least one other member
context effect
typicality depends on the context
criticism of prototype thoery
it fails to account for atypical category members and the effect of context
exemplar theory of categorization
Proposes that we store examples of items we have encountered in the past
how does categorization occur according to the exemplar theory?
Categorization occurs by comparing new items to the ones we have in memory at retrieval and looking for similarities between their features
advantages of the exemplar theory
it accounts for typicality and context effects
criticisms of the exemplar theory
it seems unlikely that we store copies of all the items we have previously encountered in memory. both exemplar and prototype theories are based on similarities and these are applied even to categories that are rule-based
Dopkins & Gleason, 1997 computer categorization experiment
had participants learn to categorize rectangles on a computer screen into two different categories. They weren’t given any rules to help them learn to sort the rectangles and were simply told if they had classified each rectangle correctly. The rectangles could be classified according to their length or position on the screen. Found that when participants had to categorize new, ambiguous exemplars that could theoretically belong to either category they chose to categorize them based on previously seen exemplars rather than a prototype
what theory do most researchers agree with?
most researchers agree that we are flexible in our categorization strategies
Armstrong et al., 1983 typicality ratings experiment
had participants give typicality ratings to naturally occurring categories but also to categories that have well-defined membership rules. Found that participants could give consistent typicality ratings to well-defined categories
Murphy & Medin’s similarity paradigm
there is an infinite number of ways that any two items can be similar
knowledge-based theories of categorization
We rely on our broad knowledge to explain the reasons for category membership
psychological essentialism
the idea that categories have a natural underlying true nature that cannot be stated explicitly
Murphy & Allopena, 1994 knowledge categorization experiment
discovered that participants have difficulty learning about things that don’t make sense. Demonstrates that we use our prior knowledge to explain particular combinations of features
downside of categorizing people based on psychological essentialism
it can lead to stereotyping
who is more likely to stereotype?
Participants with higher essentialist beliefs were more likely to endorse a variety of stereotypes about different groups of people
basic level categories
the level of categorization that people find most natural. It is the most cognitively efficient level that is both informative and distinctive (ex. dog)
subordinate categories
the level of category that is below the basic level. This level is more informative than the basic level but less distinctive (ex. poodle)
superordinate categories
the category level that is above the basic level. This level is more distinctive than the basic level but less informative
semantic network models
A model for how to store semantic information in computer memory became one of the most influential ways in shaping the way cognitive psychologists study semantic knowledge
Collins & Quillian’s semantic model
knowledge is stored as concepts within individual units called nodes, which are activated as a result of input from the environment. Semantic networks are organized hierarchically with superordinate categories occupying the uppermost level of the network and subordinate categories occupying lower levels. Knowledge is represented as a series of interconnected nodes.
cognitive economy
the tendency to conserve cognitive effort and resources
how do semantic networks demonstrate cognitive economy?
Semantic networks demonstrate this because a property is stored only once at the highest level in the hierarchy. We use the simplest terms that is meaningful for the situation
