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Chapter 8

Chapter 8

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Psychology 2010A/B
Terry Biggs

Andrea Loa Psych 2010A Chapter 8 - Categorization • One way to organize knowledge is to form categories • categories consist of objects and events that we have grouped together because we feel they are somehow related • five benefits from forming categories: • categorizing objects reduces the complexity of the environment • categorizing is the means by which objects of the world are identified • the third achievement is a consequence of the first two - the establishment of categories reduces the need for constant learning • categorizing allows us to decide what constitutes an appropriate action • categorizing enables us to order and relate classes of objects and events • concept identification - a task that requires deciding whether an item is an example of a concept, where concepts are typically defined by logical rules • logical rule - a rule based on logical relations, such as conjunctive, disjunctive, conditional, and biconditional rules • limitation of this approach: many categories cannot be distinguished on the basis of a simple rule • to recognize objects and reduce the need for constant learning, we have to be able to classify novel objects into a familiar category Concept Identification • Discovering Rules and Attributes • psychologists studied categorization by using the concept identification paradigm • disjunctive rule: a rule that uses the local relation or to relate stimulus attributes such as ʻsmallʼ or ʻsquareʼ • Bruner and his colleagues proposed that people solve concept-identification problems by evaluating hypotheses. • both attributes have to present to satisfy a conjuctive rule • the difficulty is caused by the requirement to learn both the relevant rule (such as a disjunctive rule) and the relevant attributes (such as large, circle) • rule learning: a concept identification task in which people are told the relevant attributes but have to discover the logical rule. • attribute learning: a concept identification task in which people are told the rule but have to discover the relevant attributes. • Critique of the Concept Identification Paradigm • criticized as highly artificial and unrelated to the categorization tasks we usually encounter in the real world. • real world categories such as clothes, tools, and vehicles are unlike the categories studied in the laboratory • category members do not have to share similar attributes with other members, but there are no or few attributes that are common to all members of the category • natural categories often have continuous dimensions (an attribute that can take on any value along a dimension) rather than the discrete dimensions studied in concept identification • natural categories are often hierarchically organized - larger categories consists of smaller categories • another limitation is that all members of a concept are equally good • typicality: the measure of how well a category member represents that category • some other numbers are better representations than other numbers • i.e. 4 is a better representation of an even number than 38 • percentage of water is not a good predictor of typicality Natural Categories • some categories contain other categories (hierarchy) • this part of the chapter looks at how hierarchies influence our behaviour • some members seem to be better representations of the category than other members • Hierarchical Organization of Categories • superordinate categories - largest categories (i.e. musical instruments) • members share only a few attributes • basic-level categories - intermediate categories in the middle of the hierarchy (i.e. drum) • subordinate categories - a small category at the bottom of the hierarchy (i.e. bass drum) • members share many attributes • Rosch tested that categorization is fastest at the basic-level • Rosch decided that experts might be very quick in making subordinate classification in their area of expertise • i.e. bird and dog experts were just as fast as making subordinate classifications than basic-level classifications • prototype: the “average” of the patterns in the category • this concept works best in the basic-level category • Loss of Categorical Knowledge • semantic dementia: progressive deterioration of knowledge about words and objects • can still retain other cognitive abilities • superordinate categories are better remembered with dementia • the node labelled “semantic representation” serves as a hub that creates a pattern of activation among the different attributes for each semantic concept. • with semantic dementia, the anterior temporal cortex - the location of this hub - deteriorates, specific attributes in the semantic network become distorted whi
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