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Semantic organization

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  1. Semantic organization • Rosch and others have argued that our categorization of the world is not an arbitrary historical accident, but reflects our psychological makeup, and hence is subject to investigation

  2. Semantic organization • Berlin & Kay (1969) investigated colour names across 100 different languages • order and frequency of colours used is consistent across cultures: • black white • red • green yellow • blue • brown • purple pink orange grey

  3. Semantic organization • I.e. If there are two words for colours they tend to be black and white; three black, white, and red; etc.

  4. Semantic organization • Rosch-Heider (1972) experiment with American-speaking subjects and members of the Dani, a stone-age New Guinea tribe • Dani only had words for black and white

  5. Semantic organization • Rosch built on a study by Brown & Lenneberg showing that the Zuni, whose language categorizes colours different from English-speakers, and North American English speakers tend to remember focal colours (e.g., pure green) better than nonfocal (e.g., purple) • Focal colours are colours that are selected to be good exemplars of particular colours

  6. Semantic organization • Experiment 1. • showed a single coloured chip, and were required to recognize it from a set of 160 chips • both U.S. and Dani subjects performed better with focal colours

  7. Semantic organization • Experiment 2 • Dani required to associate different colours with clan names; did better with focal colours than with non-focal colours • Conclusion • same colours were focal for Dani as for US subjects • therefore it is not language that makes certain colours easier to remember, but their perceptual salience

  8. Semantic organization • Why do people form categories? (Rosch,1978) • Cognitive economy; want to obtain as much information from the environment as possible with the least effort • the perceived world is a structured world; our perceptions shape the concepts that we form

  9. Semantic organization • Structure of categories • categories have a horizontal and a vertical dimension • horizontal--segmentation of categories at the same level of inclusiveness (e.g., sugar maple, silver maple) • vertical--different levels of inclusiveness

  10. Semantic organization

  11. Semantic organization • Rosch argues that the basic level of organization is the most useful level for many purposes because it provides the most information for the least effort

  12. Semantic organization • evidence to support hierarchical distinction • common attributes experiment • presented 9 taxonomies (e.g., tree, bird, fish, fruit, musical instruments, furniture, vehicle) at 3 levels • participants were instructed to list all of the attributes they could think of that were true of the items listed • few attributes at the superordinate level; significantly more at the basic and subordinate levels

  13. Semantic organization • evidence to support hierarchical distinction • motor movements • subjects were presented same materials as in previous study, and were asked to describe motor movements • basic objects were the most general classes to have motor sequences in common • similarity of shape and identifiability of averaged shape were other lines of evidence to support hierarchical distinction

  14. Semantic organization • How should concepts be represented? • Classical theory • what specifies a concept is some combination of semantic features (e.g., bird -- has feathers, wings, lays eggs, has a beak, etc.) • this model has been formally developed by Collins & Quillian, and Smith

  15. Semantic organization • How should concepts be represented? • Classical theory • problem is that many naturalistic concepts (birds, fruits, games, tools, etc.) are not rigidly defined • not all birds fly, not all games involve more than one person, are competitive etc. • Wittgenstein argued that family resemblance may be a more useful way to think about category membership

  16. Semantic organization • How should concepts be represented? • The idea of family resemblance leads to the idea that category membership is not determined by rigidly defined categories but by resemblance to a typical member • Rosch asked subjects to rate basic level words as being typical or atypical of a category (e.g., robin, ostrich, chicken)

  17. Semantic organization • How should concepts be represented? • results: subjects were very consistent in their responses (i.e, robin rated as typical) • subsequent study showed that verification was faster as well (robin is a bird is faster than chicken is a bird) for typical than for atypical categories • Rosch showed that typical instances had many features in common with other members of the category

  18. Semantic organization • Semantic relatedness is a general finding in this literature • prototypical members of a category are verified quickly • related negative instances of a category are verified more slowly (e.g., potato is a tree takes longer to verify than does rifle is a tree) Kintsch, 1980 • comparison process seems to be critical; not a simple category search

  19. Semantic organization

  20. Semantic organization • Feature comparison models--Smith, Shoben, & Ripps (1974) • model assumes that concepts are represented by bundles of features, separated into those that are defining, and those that are characteristic • e.g., bird -- defining -- feathers, lays eggs • characteristic -- flies, two legs, migrates

  21. Semantic organization • Verify a sentence e.g., a robin is a bird • model postulates that subject retrieves features associated with robin and with bird; if there is a high degree of overlap respond yes • if there is less overlap begin a second slower stage in which the defining features are compared; if there is overlap respond yes; if there is a mismatch respond no

  22. Semantic organization • Semantic network theories • Collins & Quillian • hierarchical memory structure model (see page 261 Reed) • critical assumptions: cognitive economy and a hierarchical model • features that are true of all animals such as eating and breathing are stored at the highest level

  23. Semantic organization • Semantic network theories • prediction: takes longer to respond to a true false question the further away the two types of information are stored

  24. Collins & Quillian 1969

  25. Collins & Quillian, 1969

  26. Collins & Quillian, 1969 • Results were consistent with the hierarchical model with cognitive economy • However, Conrad (1972) showed that if you control for relatedness, the level effect disappears • also model has difficulty accounting for typicality effects of Rosch

  27. More recent semantic networks • Spreading activation model of Collins and Loftus • see your text

  28. More recent semantic representations • Schemas, frames, and scripts • in 1932 Bartlett proposed that people remember new material in terms of existing structures of knowledge that he dubbed schemas or schemata • schemas represent some aspect of the environment, or our experience, or beliefs • learning was conceptualized as an active process in which people attempted to make sense of what they had experienced • effort after meaning

  29. More recent semantic representations • Schemas, frames, and scripts • Bartlett studied effects of schemas on memory by investigating memory for a North American folk tale (structured but unfamiliar material) • showed that the students tended omit material that was strange to them or to distort it in ways that fit their expectations • criticism--model too vague to be testable

  30. More recent semantic representations • Schemas, frames, and scripts • with the advent of computers and the cognitive approach to psychology scientists have begun to actively investigate these knowledge structures • Minsky, Rumelhart, Schank, Abelson, Kintsch, Anderson

  31. More recent semantic representations • Schemas, frames, and scripts • characteristics of this approach • this type of knowledge structure enables people to make sense of partially observed or described situations • e.g., the man bought a candy bar. People typically would infer that in money was given in exchange for the candy bar • e.g., the man drove in a nail

  32. More recent semantic representations • Schemas, frames, and scripts • characteristics of this approach • schemas have variables: buying something in a store; knowledge structure represents that it entails an exchange of money for a good; however, the amount of money or the good is left unspecified • hammering: there is a tool (hammer), an object or recipient of the action (nail), an action (hammering motion), and an agent or person

  33. More recent semantic representations • Schemas, frames, and scripts • characteristics of this approach • schemas can embed within each other • schemas operate at many levels of abstraction • schemas represent knowledge of belief • schemas are active recognition devices

  34. More recent semantic representations • Schemas, frames, and scripts • Thorndyke (1977) studied the role of story structure on recall • original version had a theme and then a narrative that elaborated the theme • version 2: narrative then theme (after theme) • version 3: narrative no theme • version 4: randomly ordered

  35. Thorndyke 1977

  36. Thorndyke (1977) • Conclusions • level of recall depends upon • degree of structure provided in the story • level of importance of the information (hierarchy level) • these two factors interact. Importance of information is evident only in structured stories

  37. Schank: scripts • Schank and Abelson hypothesized that we have developed scripts that represent commonly experienced social events • e.g., going to a restaurant • e.g., going to a bank, taking a bus

  38. Schank: scripts • Restaurant script • Props: restaurant, tables, menu, food, bill, money, tip • Agents: customer, waiter, cook, cashier, owner • Entry conditions: customer hungry, customer has money • Results: customer has less money, owner has more money, customer is not hungry

  39. Schank: scripts • Restaurant script • Scene 1: entering • customer enters restaurant • customer looks for table • customer decides where to sit • customer goes to table • customer sits down • Scene 2: ordering • Scene 3: eating • Scene 4: exiting

  40. Neuropsychology of semantic memory • Visual agnosia (Lissauer, 1888) • GL sustained a blow to the head • complained of difficulty seeing • examination showed normal visual acuity • normal ability to copy objects • recognition of objects was severely impaired; but it was not a general deficit; e.g., unable to recognize a whistle when presented visually, but able to recognize a whistle from its sound

  41. Neuropsychology of semantic memory • Tactile agnosia (Beauvais, 1978) • patient unable to recognize objects to touch, but could recognize objects when they were presented visually • also patient was able to use objects appropriately • these results suggest that semantic memory is not a single unitary system, but has a number of subcomponents associated with the modality of input

  42. Neuropsychology of semantic memory • Warrington & Taylor (1978) showed that subjects with brain injury made two types of semantic errors in the visual modality • access disorder--some subjects had difficulty recognizing a picture of an object (e.g., tennis racquet) • degraded semantic store--other subjects recognized the object, but had difficulty recognizing which object was commonly associated with the object (e.g., a tennis ball)

  43. Neuropsychology of semantic memory • Warrington & Shallice (1979) proposed the following criteria to distinguish access versus degraded semantic store impairments • consistency--if deficit is degraded semantic store, there should be consistency across test sessions (and type of test, Bayles) • On the other hand if the problem is one of access, then one might expect that different types of retrieval cues might lead to retrieval of the item • priming--patient should not show priming effects if there is a degraded store; however, certain primes might facilitate access to items if the problem is one of access

  44. Neuropsychology of semantic memory • Structure of semantic memory: modality specificity or a single semantic store? • one view holds that semantic memory consists of a single amodal system • second view hypothesizes that there are separate systems for verbal, visual, and other types of information • the evidence at this point is not yet entirely clear on this point

  45. Neuropsychology of semantic memory • How are other types of information represented in semantic memory? • Some evidence suggests that evaluative information is processed and stored in a different location than denotative information

  46. Case Description of AM • Successful businessman prior to TBI • Average to very superior general intellectual functioning • Normal academic, attention, and executive function abilities • Generally intact memory abilities • Poor social judgment; everything is positive Park et al. (2001) Neuropsychologia

  47. R.Temporal Temporal L.Amygdala b a Amygdala Frontal c d

  48. Attitude Priming Study of AM • Purpose: to investigate AM’s evaluative rating of words • Hypothesis: impaired automatic evaluation of negative but not positive evaluative stimuli Park et al. (2001) Neuropsychologia

  49. Attitude Priming (continued) • Method: attitude priming paradigm • Participants: AM and 8 age - and education -matched controls • Procedure: • Phase 1: rate single words as “good” or “bad” • hypothesized positivity bias Park et al. (2001) Neuropsychologia