8.1 | The Organization of Knowledge

Question 1

Concepts and Categories

Answer 1

• concept: the mental representation of an object, event, or idea
• categories: clusters of interrelated concepts
• categorization: the process of forming these groups

Question 2

Classical Categories: Definitions and Rules

Answer 2

• classical categorization: this theory claims that objects or events are categorized according to a certain set of rules or by a specific set of features
• we use a variety of cognitive processes in determining which objects fit which category
• graded membership: the observation that some concepts appear to make better category members than others
  
  • sentence-verification technique: experiments in which volunteers wait for a sentence to appear in front of them on a computer screen and respond as fast as they can with a yes or no answer
  • e.g. “A sparrow is a bird” or “A penguin is a bird”
  • these experiments show us that some members of a category are recognized faster than others

Question 3

Prototypes: Categorization by Comparison

Answer 3

• prototypes: mental representations of an average category member
• no rules or definitions are involved, just a set of similarities in overall shape and function
• the main advantage of prototypes is that they help explain why some category members make better examples than others

Question 4

Networks and Hierarchies

Answer 4

• semantic network: an interconnected set of nodes (or concepts) and the links that join them to form a category
• nodes: are circles that represent concepts
• links: connect nodes together to represent the structure of a category as well as the relationships among different categories
• priming: when seeing one word makes connected nodes in the network more likely to become activated
• e.g. it’s easier to identify the word “oranges” from the category “fruit” after seeing the word “apple” vs. an unrelated word “elephant”
• semantic networks are organized in a hierarchy
• the basic level category is located in the middle row of figure 8.3 (where birds and fish are)
  
  • basic-level categories are the terms used most often in conversation
  • easiest to pronounce
  • level at which prototypes exist
  • level at which most thinking occurs
  • e.g. you would most likely say “There’s a bird in your yard” and not animal or robin, as the first would indicate confusion and the second suggests there’s something special/important about that classification

Question 5

Categories and the Brain

Answer 5

• initial attempts to understand how information is organized in the brain relied on patients with damage to the temporal lobes who displayed a very specific set of symptoms
• category specific visual agnosia (or CSVA): these patients had trouble identifying the objects they were seeing, but could still describe them
  
  • scientists suggested that different categories are organized in the brain based on their sensory (visual, touch, etc.) and functional features (i.e., what they are used for)
  • the damage associated with CSVA differs slightly from patient to patient, making it difficult to say with any certainty that damage to a particular area will definitely result in a deficit related to a specific category
• domain-specific hypothesis: evolutionary pressures led to the development of specialized circuits in the brain for a small group of categories that were important for survival
  
  • one weakness of this view is that it doesn’t take into account people’s different experiences with each category

Question 6

Categorization and Experience

Answer 6

• our ability to form categories is based on our experiences
• when encountering a new item, people will select its category by retrieving the item(s) that are most similar to it from memory
• we sometimes retrieve individual features (e.g. a beaver’s tail) rather than an entire object from memory
• Norman et al. (1989): experiment where medical students were taught to diagnose different skin conditions using written rules and photographs
  
  • when tested, medical students would rely on the photographs instead of the rules, which lead to false diagnoses

Question 7

Culture and Categories

Answer 7

• categorization is based (to some extent) on cultural learning
• linguistic relativity (or the Whorfian hypothesis): the theory that the language we use determines how we understand the world
• however, the differences in vocabulary does not necessarily lead to differences in perception