PSYC 2650 Chapter 9: Chapter 9

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16 Nov 2017
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Chapter 9 Concepts and Generic Knowledge
Understanding Concepts
Ordinary concepts (“shoe” or “tree”) are the building blocks out of which all your
knowledge is created you depend on your knowledge in many aspects of your day-to-
day functioning
You need concepts in order to have knowledge, and you need knowledge in order ot
function
Definitions: What is a “Dog”?
You have knowledge that represents what a dog is for you; but what is that knowledge
o You know something akin to a dictionary definition
“A dog is a creature that (a) has four legs, (b) barks, (c) wags it’s tail.”
Can use the definition as a checklist
But what about more complex concepts?
o For each clause of the definition, we can easily find an exception that doesn’t
have the relevant characteristic
Therefore, that even simple terms, terms denoting concepts we use easily and often, resist
being defined
o In each case we can come up with what seems to be a plausible definition, but
then its easy to find exceptions to it
Family Resemblance
Associate that we’ve seen one dog with four legs so all dogs must have four legs
Dogs usually are creatures that have fur, four legs, and bark, and a creature without these
features is unlikely to be a dog
o This probabilistic phrasing preserves what’s good about definitions the fact that
they do name sensible, relevant features, shared by most members of the category
A degree of uncertainty, some number of exceptions to the rule
Members of a category have a family resemblance to one another
o There are features that are common in the family, and so, if we consider family
members two or three at a time, we can usually find some shared attributes
o There are common features, but the identity of those common features depends on
what “subgroup” of the family you’re considering – hair colour shared for these
family members; eye shape shared by those family members
Imagining the “ideal” for each family someone who has all of the family’s features
o In lots of families, it may not exist
o Each member of the family has at least some features in common with this ideal
and therefore some features in common with other family members
Ordinary categories (“dog”) work the same way
o There may be no features that are shared by all dogs, but we can identify
“characteristic features” for each category – features that many category members
have.
o The more of these features an object has, the ore likely you are to believe it is in
the category
o Family resemblance is a matter of degree, not all-or-non**
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Prototypes and Typicality Effects
Definitions set the “boundaries” for a category
o If a case has certain attributes, then it’s “inside” the boundaries; if if a test doesn’t
have the defining attributes, then it’s “outside” the boundaries
Prototype theory begins with a different tactic: Perhaps the best way to identify a
category is to specify the “center” of the category, rather than the boundaries
o Perhaps the concept of dog is represented in the mind by some depiction of the
“ideal” dog, and all judgements about dogs are made with reference to this ideal
The concept is represented by the appropriate prototype
In most cases the ideal (the prototype) will be an average of the various category
members you’ve encountered
o Prototype dog average colour, average size, etc., for all the dogs you have seen
o No matter what the specifics of the prototype, though, you’ll use this “ideal” as
the anchor, the benchmark for your conceptual knowledge whenever you use
your conceptual knowledge, your reasoning is done with reference to the
prototype
Prototypes and Graded Membership
Simple task of memorization: deciding whether something is or is not a dog
o To make decision you compare the creature currently before your eyes with the
prototype in your memory
o If there is no similarity between them, the creature standing before you is
probably not in the category; if there’s considerable similarity, you draw the
opposite conclusion
Membership in a category depends on resemblance to the prototype, and resemblance is a
matter of degree
o As a result, membership in the category is not a simple yes or no decision it’s a
matter of more or less
o Categories have a graded membership objects closer tot the prototype are
“better” members of the category than objects further from the prototype
Some dogs are “doggier”
Testing the Prototype Notion
In a sentence verification task research participants are presented with a succession of
sentences; their job is to indicate whether each sentence is true or false
o According to the prototype perspective, participants choose their response (true vs
false) by comparing the thing mentioned to their prototype for that category
o When there is close similarity between the test case and the prototype,
participants can make their decisions quickly; judgments about items more distant
from the prototype take more time
Production task ask people to name as many birds or dogs as they can
o According to prototype view they will do this task by first locating their bird or
dog prototype in memory and their asking themselves what resembles this
prototype
o They’ll start with center of category and work their way outward from there
o Birds close from the prototype mentioned first
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