Methods of Cognitive Science

1. Methods of Cognitive Science • Psychological measures • Self-reports • Speed of responses • Analysis of errors • Neurological methods • Brain damage studies • Brain imaging techniques

4. Computer science • Programming; computational models • Turing test • Philosophy: method of analogy

5. Example: Child adds 4 + 3 = 7 • Possible models: • Child has memorized answer and “looks it up” • Child is using a counting algorithm • Which model is correct? • Ask child to think aloud • Time responses to “4 + 1” and “4 + 3” • Examine nature of errors • What parts of brain are active while counting? While searching memory?

6. Levels of description • Behavioral (knowledge) level • Addresses competence, not underlying algorithms • Cognitive (formal) level • Analyzes the algorithm that information processor is using • Biological (physical) level • Tells us about physical structures from which cognition arises

7. Example: Language development • Behavioral level: • Very young child says “Mommy went to work” • Months later, “Mommy goed to work” • Still later, “Mommy went to work” again • Formal level: • Very young child: simple imitation • Months later, algorithm of “add -ed” for past • Still later, algorithm plus idea of irregular past tenses (exceptions to the rule)

8. Physical level: • What parts of the brain are active as child learns language? • What nerve connections are forming as child’s skill develops?

9. Cognitive Architecture • Building’s architecture: formal structure or plan of a building • Computer architecture: fixed processing structure underlying the design of the machine • Cognitive architecture: fixed structure that allows intelligent behavior

10. Characteristics of acognitive architecture • Should be cognitively impenetrable • Cannot be caused to change function simply by changing its goals or knowledge • Like a reflex: fast, automatic, innate • Opposite of cognitively penetrable: • Changes in goals/knowledge lead to changes in function • Cannot reflect underlying architecture of mind

11. But are there cognitive reflexes? • Müller-Lyer illusion

12. But are there cognitive reflexes? • Müller-Lyer illusion • Knowledge of the facts does not alter perception • Occurs immediately • Innate? (Some dispute over this) • Illusion of self-motion • Phonemic restoration effects • Perceptual constancies

13. Characteristics of a cognitive architecture • Should be cognitively impenetrable • Need for independent mental modules

14. Properties of mental modules • Domain-specific • Takes limited set of stimuli as input • Performs a particular set of operations • Limited range of output • Informationally encapsulated • Restricted to its own knowledge base • Does not draw upon full range of goals, knowledge, beliefs of overall system

15. Properties of mental modules • Domain specific • Informationally encapsulated • Mandatory - we cannot escape them • Speedy • MAY involve localization in the brain

16. The Language Module • Language processing = fast, automatic, probably innate • McGurk effect

17. The McGurk Effect • See video of person pronouncing “ga ga” • Hear audio of person pronouncing “ba ba” • What do we perceive? Something in between - “da da” or “bag ba” or “gab ga”

18. The Language Module • Language processing = fast, automatic, probably innate • McGurk effect • Development of language in deaf children • Double dissociations between language and other cognitive abilities • Aphasias • Linguistic savants

19. The Language Module • Language processing = fast, automatic, probably innate • Double dissociations between language and other cognitive abilities • Evidence for fixed neurological structures involved in language • Basics of grammatical parsing are informationally encapsulated