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Chapter 8

PSYB57 - Cognition ch.8

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Pare, Dwayne

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PSYB57 – Chapter 8: Concepts and Generic Knowledge Definitions: What Is a Dog?  there are dictionary definitions for some words for example “dog” o a dog is a mammal, has four legs, barks and wags its tail  in order to define commonplace concepts, Ludwig Wittgenstein argues that the simple terms we use every day actually don’t have definitions o how would one define “a game” o a game is defined as an activity that has certain rules, is practiced by children, is engaged in for fun, involves multiple players, is in some ways competitive, and played during periods of leisure o this definition cannot be applied to the Olympic games even though they are still considered a game, or gambling or even professional golfers  for each clause of the definition, we can easily find an exception  even simple terms, terms denoting concepts we use easily and often, resist being defined, we can come up with what seems to be a plausible definition, but then it’s easy to find exceptions to it Family Resemblance  it is better to say that “dogs usually are creatures that have fur, four legs, and bark and a creature without these features is unlikely to be a dog”  this probabilistic phrasing preserves what’d good about definitions and allows degree of uncertainty  Wittgenstein proposed that members of a category have a family resemblance to each other  There are common features, but the identity of those common features depends on what “subgroup” of the family you are considering (ex. Hair color shared by family, eye color shared by family)  Each member of the family has some features in common with an ideal, and therefore some features in common with other family members and that is why family members resemble each other (ideal is someone who has all the family features; not all families have this person)  Just as the example with the “dog” and “game”, there may be no features that are shared by all dogs or games, just as there are no features shared by everyone in a family,  We can identify characteristic features for each category which many of the family members have and the more of these features an object has, the more likely you are to believe it is in the category  FAMILY RESEMBALECE IS A MATTER OF DEGREE, NOT ALL-OR-NONE Prototypes and Typicality Effects  Definitions set boundaries for a category  The prototype theory: the best way to identify a category and to categorize a concept is ot specify the center of the category, rather than make boundaries o Ex. The concept of dog is represented in the mind by some depiction of the ideal dog and all judgments about dogs are made with reference to this ideal  A prototype literally represents the ideal for the category  It will be an average of the various category members o Ex. The prototype dog will be the average color of the dogs you have seen and the average size etc.  Different people may have different prototypes  If a prototype reflects the ideal for a category, people may disagree about what the ideal would be and that is why we need some flexibility in how we characterize prototypes  A PROTOTYPE WILL SERVE AS THE ANCHOR, BENCHMARK, FOR OUT CONCEPTUAL KNOWLEDGE, AND WHEN WE USE THAT CONCEPTUAL KNOWLEDGE, THE REASONING IS DONE WITH REFERENCE TO THE PROTOTYPE Prototypes and Graded Membership  Membership in a category depends on resemblance to the prototypes and resemblance is a matter of degree  Categories have a graded membership, such that objects closer to the prototype are better members of the category than objects farther from the prototype o Ex. Some dogs are “doggier” than others, some books “bookier” than others etc. Testing the Prototype Notion  Sentence verification task: participants are presented with sentences and they have to indicate whether each sentence is true or false. Their response times are tested and they vary for from item to item. Response times are longer for sentences like “a penguin in a bird” than for “a robin is a bird” o The participants make judgments by comparing the thing mentioned to their prototype for that category o When there is much similarity between the test case and the prototype, participants can make their decisions quickly  Production task: ask people to name as many birds or dogs or any other category o To do this task, the person will first locate the bird or dog prototype in their memory and ask themselves what resembles the prototype o For example, birds close to the prototype will be mentioned first whereas birds farther from the prototype will be mentioned later on  What matters in both tasks is proximity to the prototype  Prototype theory: over and over, in category after category, members of a category that are privileged on one task turn out also to be privileged on other tasks (ex. Fast response times are related to most likely mentioned objects) o Various tasks converge in the sense that each task yields the same answer and indicates the same category members as special  Rating task: participants are presented with a list of a category such as birds or dogs and they are to rate each one on the basis of how “birdy” or “doggier” it is o They rated the items as less “birdy” or “doggy” when they were far from the prototype o This suggests that people perform this task by comparing the test item to the prototype  When people think about a category they are actually thinking about the prototype for that category o When participants were asked to make up sentences using the list of birds in a study, they came up with statements that were appropriate for the prototype. The words that had the highest ratings of being “birdy” were the ones used for the sentence o The meaning of the sentence should be unchanged if the word is replaced by another word of the same prototypical category Basic-Level Categories  Just as some category members are privileged, categories themselves are also privileged  There is a natural level of organization that is not too specific and not too general that we tend to use in everyday convos and reasoning = basic-level categorization  Basic-level categorizations are represented via a single word while specific categories are identified by a phrase o Ex. “chair” is basic level category whereas “lawn chair” or “kitchen chair” are specific (subordinate) categories  If asked to describe an object we are most likely to use the basic-level term  It has been seen through studies that in children who are learning to talk, basic-level terms are often acquired earlier than either the more specific subcategories or the more general, more encompassing categories  Basic-level categories do seem to reflect a natural way to categorize the objects in our world Exemplars  Some members of categories are better than others and the better members are recognized faster and more readily, mentioned more, judged more typical and so on  Conceptual knowledge is represented via a prototype and that we categorize by making comparisons to that prototype Analogies From Remembered Exemplars  In some cases, categorization can draw on knowledge about specific category members rather than on more general info about the overall category.  Ex. After a showing a chair and asking what it is, one may answer by recalling that this object (chair) is in his uncle’s living room and he sits on it and it looks like the chair being shown so the object must be a chair  This is called exemplar-based reasoning, with an exemplar being defined as a specific remembered instance  The exemplar-based approach is in many ways similar to the prototype view o Similarity: categorize objects by comparing them to a mental “standard” o Difference: what is the standard; either prototype (prototype theory) or an exemplar (exemplar theory) Explaining Typicality Data With an Exemplar Model  Task: show people series of pictures and ask them to decide whether each picture shows a fruit or not o They will respond faster for typical fruits (apple, orange, banana) than less typical fruits (kiwi, cranberry)  Figuring out whether it is a fruit or not through an exemplar based approach o Think of a fruit exemplar that resembles the object in the picture. If the memory is a good match to the picture then you know the object in the picture is a fruit o How this happens depends on the picture o Ex. Since apples are common in experience and we have had many opportunities to establish memories with apples, it will be easier to find that memory since it is primed but if it a fruit that you have not encountered much such as a fig, then memory search will be more difficult  If asked to name as many fruits as you can remember, we are most likely to name the typical fruits such as apple, oranges, banana etc. because these are represented many times in our memory  Your production will favor the typical fruits not because of prototyping but because of the pattern of what is available in the memory A Combination of Exemplars and Prototypes  Both theories (exemplar and prototype) are correct; we rely on both when thinking about categories  The purpose of this double mode representation? o Prototypes provide economical representations of what is typical for a category while exemplars provide info that is lost from prototype (people can tune their concept to match the circumstance; people think about Chinese birds differently from American birds) o People can adjust their categories in precise ways  Gift vs gift for a 4-year-old vs a gift for a 4-year-old who just broke her arm  Conceptual knowledge includes both prototypes and exemplars because each carries its own advantages  The mix of both knowledge may vary from person to person and from concept to concept  The pattern of knowledge might depend on the size of the category and on how confusable the category memories are with each other  The pattern or knowledge can also change for a particular person: when first learning about palm trees, you would use exemplar knowledge to think about them later but with more and more experience with palm trees, you will begin to rely on prototype knowledge  Exemplar and prototype models reply on the same processes, triggering of a memory, judgment of resemblance, and conclusion based on the resemblance The Difficulties With Categorizing via Resemblance  For most concepts, definitions are not available  Typicality plays a huge role in people’s thinking, with more-typical category members being privileged in many regards The Difference Between Typicality and Categorization  Judgments of typicality and judgments of category membership both derive from the same source: resemblance to an exemplar or prototype  If the resemblance is great then a test case will be judged to be typical and will also be judged to be a category member so typicality and category membership should go hand in hand but they always don’t  Participants were asked to rate how even/odd a number is given a list of even/odd numbers o They thought 4 was more even that 7534 even though they are both even numbers o This shows that there is some basis for judging category membership that is separate from the assessment of typicality, and there is no explanation for that point in the theory  These results tell us that category judgments can be made on some basis other than typicality but what is that other basis (deep features)  If a lemon is colored red and injected with sugar and crushed under a truck it will still be a lemon  In a study preschool children were asked what makes something a coffeepot or a raccoon etc. they were asked if they can turn a toaster into a coffeepot and they said that is
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