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The Work of Betty Tuller and Complex Systems

The Work of Betty Tuller and Complex Systems. John Cadwallader PSB 4065. Complex Systems. Composed of a large number of simple agents interacting with one another according to specified rules. Share universal patterns. Complex Systems. Examples: Molecules in a liquid Genes in a cell

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The Work of Betty Tuller and Complex Systems

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  1. The Work of Betty Tuller and Complex Systems John Cadwallader PSB 4065

  2. Complex Systems • Composed of a large number of simple agents interacting with one another according to specified rules. • Share universal patterns.

  3. Complex Systems • Examples: • Molecules in a liquid • Genes in a cell • Organisms in an ecosystem • Buyers/sellers in an economy • ISPs on the internet • Neurons in a brain?!?!?

  4. Complex Systems • Share Common Properties: • Phase transitions • Order parameter(s) • Control parameter(s) • “Slaving” • Enhanced contrast • Hysteresis • Others…

  5. Phase Transitions • Rayleigh-Bernard Instability

  6. Order and Control Parameters

  7. Slaving • Analogy: state of an army can be described without reference to any individual soldier. The state of every soldier is a slave to the state of the army. In understanding the system we don’t have to worry about every single degree of freedom.

  8. Hysteresis

  9. How does all of this apply to behavior?

  10. Speech Categorization: Tuller et al. 1994 • How do we determine what a person’s utterance means? • Different people say the same word differently. • The same word can sound different in different environments. • Same-sounding words can have different meanings.

  11. Speech Categorization: Tuller et al. 1994 • Used a “say” – “stay” continuum • Varied the gap between the “s” and the rest of the word.

  12. Speech Categorization: Tuller et al. 1994 • Order parameter: interpretation of stimulus • Control parameter: interval between s and rest of word • Patterns: • Hysteresis • Enhanced contrast • Indicative of complex systems-like behavior

  13. Speech Categorization: Tuller et al. 1994

  14. P. Kruse et al 1996 • The perception of multistable visual objects • Different groups of lights flash alternately

  15. P. Kruse et al 1996 • Percepts range from: • No apparent motion • Alternating motion • Unidirectional motion • Bidirectional motion • All lights appear on simultaneously

  16. P. Kruse et al 1996 • Order parameter: type of motion observed • Control parameter: interval between lights

  17. P. Kruse et al 1996

  18. Freeman 1997 • Olfactory coding • How does olfactory bulb recognize different odors? • No one-to-one correspondence between odorant and cells in the olfactory bulb. • Even lesioning areas of the bulb that are most activated by a particular odorant does not prevent the animal from recognizing the odorant.

  19. Freeman 1997

  20. Conclusions • Complex systems approach offers powerful method for understanding macro-scale brain function • Also offers direct path for simulating brain function on computers, something the cognitive approach and behavioristic approach do not allow (in any straightforward manner)

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