HPS203 Lecture Notes - Lecture 9: Motor Cortex, Knowledge Network, Coffeemaker
HPS203 Week 9
TOPIC 6: CONCEPTS AND GENERIC KNOWLEDGE
Explain why our definitions of basic concepts like ‘dog’ often fail
• It seems that for each clause of the definition, we can easily find an exception
• We might define ‘dog’ in a way that includes four-leggedness, but what about a dog that
has lost a limb in some accident?
• We might specify ‘communicates by barking’ as part of the definition of a dog, but what
about the Egyptian basenji, which has no bark?
• Examples like this make it clear that even simple terms, terms denoting concepts we use
easily and often, resist being defined
Define family resemblance
• Family resemblance: the notion that members of a category (e.g. all dogs, all games)
resemble each other
o In general, family resemblance relies on some number of features being shared by any
group of category members, even though these features may not be shared by all members
of the category.
o Therefore, the basis for family resemblance may shift from one subset of the category to
another.
• There are common features, but the identity of those common features depends on what
‘subgroup’ of the family you’re considering
Describe prototype theory and what is meant by graded membership
• Prototype theory: the claim that mental categories are represented by means of a single
‘best example’, or prototype, identifying the ‘center’ of the category.
o In this view, decisions about category membership, and inferences about the category, are
made with reference to this best example, often an average of the examples of that
category you have actually encountered.
• Different people may have different prototypes; people will disagree about what the
‘ideal’ would involve
o An American’s prototype for ‘house’ might have one form, but someone who lives in
Japan will differ
• In all cases, the prototype will serve as the anchor, the benchmark, for our conceptual
knowledge
o Your reasoning is done with reference to the prototype
• Graded membership: the idea that some members of a category are ‘better’ members and
therefore are more firmly in the category than other members
• Membership in a category depends on resemblance to the prototype, and resemble is a
matter of degree
• As a result, membership in the category is not a simple ‘yes’ or ‘no’ decision; instead, it’s a
matter of ‘more’ or ‘less’
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Describe how the production task and the rating task demonstrated evidence for using
prototypes to judge category membership
• Production task: an experimental procedure used in studying concepts, in which the
person is asked to name as many examples (e.g. as many fruits) as possible
• e.g. When asked to name as many birds or dogs as possible; according to a prototype
view, they will do this task by:
o First locating their bird or dog prototype in memory
o Asking themselves what resembles this prototype
o Starting with the centre of the category (the prototype)
and working their way outwards – e.g. birds close to the prototype mentioned first, birds
farther from the prototype later on
• Rating task: a task in which research participants must evaluate some item or category
with reference to some dimension, usually expressing their response in terms of some
number
o For example, participants may be asked to evaluate birds for how typical they are within
the category of ‘birds’, using a ‘1’ response to indicate ‘very typical’ and a ‘7’ response to
indicate ‘very atypical’
• They rate items as less ‘birdy’ or ‘doggy’ when they are farther from the prototype
• Once again, people perform this task by comparing the test item to the prototype
Define basic level categories
• Basic-level categorisation: a level of categorisation hypothesised as the ‘natural’ and most
informative level, neither too specific nor too general
o People tend to use basic-level terms (such as ‘chair’, rather than the more general
‘furniture’ or the more specific ‘armchair’) in their ordinary conversation and in their
reasoning
• Basic level categories are usually represented in our language via single word
• If asked to describe an object, you’re more likely to use the basic level term
• When learning to talk, children usually acquire basic level terms earlier than more specific
subcategories, or more general encompassing categories
• Basic-level categories seem to reflect a natural way to categorise objects in our world
Define exemplars
• Exemplar-based reasoning: reasoning that draws on knowledge about specific category
members, rather than drawing on more general information about the overall category
• In some cases, categorisation can draw on knowledge about specific category members
rather than on more general information about the overall category
• Exemplar: the specific remembered instance – in essence, an example
Define the main similarities and differences between the prototype and exemplar theories
of categorisation
• For prototype theory, the standard is a prototype – an average representing the entire
category
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• For exemplar theory, the standard is provided by whatever example of the category
comes to mind
• In either case, the process is the same
o You assess the similarity between a candidate object and
this standard
o If the resemblance is great, you judge the candidate as
being within the relevant category
o If the resemblance is minimal, you seek some alternative
categorisation
• Prototypes provide an economical representation of whats typical for a category. This
quick summary is quite useful
• Exemplars provide information that is lost from the prototype e.g. people routinely tune
their concepts to match circumstances, and so they think about gifts differently when
thinking about gifts for a student rather than gifts for a faculty member. People can adjust
their categories in very precise ways e.g. gift for a 4 year old who recently broke her wrist.
• If people are relying on exemplars- different settings, different perspectives would trigger
different memories and bring different categories to mind. If someone is then relying on
these exemplars in his reasoning, it makes sense that his reasoning will vary from one
circumstance to the next.
Both have advantages
• If you had only seen a couple of palm trees- you you’ll rely on exemplar knowledge
• With more experience of palm trees, you’ll rely more on prototype knowledge
Describe a situation in which categorisation and resemblance do not go ‘hand in hand’
• Armstrong, Gleitman and Gleitman (1983) gave their participants this peculiar instruction:
“We all know that some numbers are even-er than others. What I want you to do is rate
each of the numbers on this list for how good an example it is for the category ‘even
number’.”
• Participants responded differently and correctly if asked directly which numbers on the list
were even and which were odd
• Judgments of categorisation and judgments of typicality were independent of each other
o Participants believed that 4 is a more typical even number than 7534, but also knew that
this has nothing to do with the fact that both are unmistakably in the category even number
Explain what else we use to make category judgments over and above typicality
• What counts as essential depends on your understanding of that category e..g. parentage
(still a racoon even though it looks like a skunk, as born by two racoons), printing (not a note
unless printed under supervision of government agency) etc.
• Our understanding of category is also guided by wed of other beliefs e..g knowledge of
biological inheritance & monetary systems.
Further explanation:
• Category membership is not based on resemblance alone e.g. a
painted lemon that has been run over by a truck doesn’t look
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Document Summary
Describe prototype theory and what is meant by graded membership: prototype theory: the claim that mental categories are represented by means of a single. Ideal" would involve: an american"s prototype for house" might have one form, but someone who lives in. Define basic level categories: basic-level categorisation: a level of categorisation hypothesised as the natural" and most informative level, neither too specific nor too general, people tend to use basic-level terms (such as chair", rather than the more general. If someone is then relying on these exemplars in his reasoning, it makes sense that his reasoning will vary from one circumstance to the next. Both have advantages: if you had only seen a couple of palm trees- you you"ll rely on exemplar knowledge, with more experience of palm trees, you"ll rely more on prototype knowledge. Describe a situation in which categorisation and resemblance do not go hand in hand": armstrong, gleitman and gleitman (1983) gave their participants this peculiar instruction:
