Dissociable Systems in Cognition

1. Dissociable Systems in Cognition Psychology Honours 2007 John C. Dunn

2. Aim • To address the general problem of how to draw inferences about the structure of cognitive processes from observed patterns of behaviour

3. Plato’s Allegory of the Cave http://home.lbcc.cc.ca.us/~mlawrence/Phil%206/platosCave%20copy.jpg

4. A modern Plato’s cave:X-ray crystallography

5. Observed data Inferred structure Inference in x-ray crystallography

6. Experimental situation Instructions Proximal stimulus Response Cognitive Psychology http://www.colby.edu/psychology/labs/PercepAction/Info_Pend.jpg

7. Observed data Inferred structure Inference in cognitive psychology

8. Two kinds of inference • Top-down (deductive) • Derive precise prediction from theory • Conduct experiment • Compare prediction to experiment • Bottom-up (inductive?) • Make general set of assumptions • Observe data • Identify theories that are consistent with observed data and assumptions

9. Course outline • The nature of the problem • A possible solution: functional dissociations • Beyond dissociations • Performance resource functions • Reversed association • Conceptual breakthrough • State trace analysis • Applications • Loftus et al. (2004) • Dunn (2007)

10. Functional dissociation • “Dissociations are used to infer the existence of separate mental processes. There are two main types, single and double. Let A and B be two tasks and let a and b be two manipulations, variables or factors. A single dissociation is observed if a affects performance on A but not on B. A double dissociation is observed if, in addition, b affects performance on B but not on A.” • Dunn & Kirsner (2003, p. 1)

11. Functional dissociation

12. Observed data a b a b A B A B Inferred structure P Q Functional dissociation

13. Some examples of dissociation logic • Glanzer & Cunitz (1966) • Graf & Schacter (1985) • Curran (2000) • Ashby, Maddox, & Bohil (2002)

14. Glanzer & Cunitz (1966) • “The aim of this study is … to test the hypothesis that there are two distinct storage mechanisms that produce the serial position curve in free recall.” • “The strategy is to use variables which should have one effect on one storage mechanism and a different effect (either no effect or an opposed effect) on the other storage mechanism.” • “[Manipulation of] these variables should give predictable changes in the shape of the serial position curve” • p. 352

15. Recency part Primacy part Serial Position Curve

16. Experiment 1 • Hypothesized factors that may selectively affect long term store but not short term store: • Presentation rate • 1 item per 3 s, 6 s, 9 s • Item repetition • 1, 2, 3 repetitions at 3s rate • Results: • Presentation rate affected primacy part of curve • Item repetition had no effect • Neither factor affected recency part of curve

17. Repetition Presentation Rate

18. Experiment 2 • Hypothesized a factor that may selectively short term store but not long term store: • Duration of filled retention interval (counting backwards) • 0, 10, 30 s • Results: • Factor had large effect on recency part of the curve • Had little or no effect on primacy part of curve

19. Retention Interval

20. Observed data Presentation rate Primacy Duration of interval Recency Inferred structure LTS Presentation rate Primacy STS Duration of interval Recency Summary

21. Graf & Schacter (1985) • Investigated “implicit memory for new associations” • “Implicit memory is revealed when performance on a task is facilitated in the absence of conscious recollection; explicit memory is revealed when performance on a task requires conscious recollection of previous experiences.” (p. 501) • Compared direct vs indirect memory tests

22. Direct vs indirect memory tests • Direct tests • Solution depends upon information presented in the study phase • Free recall • Cued recall • Item recognition • Indirect tests • Solution does not depend (but may be facilitated by) information presented in the study phase • Facilitation often called priming • Naming • Lexical decision • Word fragment completion • Word stem completion

23. Big theoretical question • Do direct and indirect tests depend upon the same or different memory systems, processes, components?

24. Less big theoretical question • Many direct tests depend upon the formation of associative links between items and/or items and context • Requires involvement of episodic memory • Priming on many indirect tests can be explained in terms of activation of pre-existing representations • Does not appear to require involvement of episodic memory • Can we find evidence of priming for newly formed associations that does not depend upon episodic memory?

25. Implicit memory for new associations • Graf & Schacter (1985, Experiment 1) • Study phase: • Related word pairs: • RIPE-APPLE • COVERING-BLANKET • Unrelated word pairs: • KINDLY-STICK • DRYER-BLOCK • Test phase (word stem completion) • Same context: RIPE-APP___ • Different context: DRYER-BLA___ • Found more priming in same context condition but only under elaborative encoding instructions • Although nominally an implicit or indirect memory test, results may have been contaminated by conscious recollection

26. Graf & Schacter (1985)Experiment 2 • Compared amnesic and control subjects • Amnesics have impaired episodic memory (conscious recollection) • If implicit memory for new associations depends upon conscious recollection (explicit memory) then amnesics should be impaired on this task

27. Graf & Schacter (1985)Experiment 2 • Study phase: • Related word pairs: • RIPE-APPLE • COVERING-BLANKET • Unrelated word pairs: • KINDLY-STICK • DRYER-BLOCK • Elaborative encoding instructions • 3 Groups: • Amnesics • Matched controls • Student controls

28. Graf & Schacter (1985)Experiment 2 • Test phase: • Word stem completion • Same context • Related word pairs: RIPE-APP___ • Unrelated word pairs: DRYER-BLO___ • Different context • COVERING-STI___ • Cued recall • Related word pairs: RIPE-____ • Unrelated word pairs: DRYER-____

29. Results:Cued recall

30. Results:Word stem completion

31. Conclusions • “The amnesic group’s data provide critical evidence in support of the view that the same-different effect on the word completion test is mediated by implicit memory for new associations.” • “Thus, the present findings support the view that implicit and explicit memory for new associations are mediated by different underlying processes”. • Graf & Schacter (1985, p. 512)

32. Double dissociation

33. Observed data Amnesia Cued recall Relatedness Word stem completion Inferred structure Amnesia Cued recall E Relatedness I Word stem completion Conclusions

34. Curran 2000 • Event-related brain potential (ERP) experiment • Based on dual process model of recognition memory • Recognition memory depends on recollection and familiarity • Test hypothesis that these processes differentially affect two ERP components • FN400 (frontal region 300-500ms post-stimulus) • Parietal region (400-800ms post-stimulus)

35. Event-related potentials Scalp topography Time

36. Parietal Frontal Electrode placement:Regions of interest

37. Plurals paradigm • Recognition memory experiment • Study phase • Words in plural and singular form • e.g. TABLE, CHURCHES • Test phase • Studied words, e.g. TABLE • Similar lures, e.g. CHURCH • New lures, e.g. YACHT • Dual process interpretation • Studied item/ yes response • High familiarity, recollected • Similar item/ yes response • High familiarity, not recollected • New item / no response • Low familiarity, not recollected

38. Results

39. Inferred structure F Similar [yes] vs. New [no] FN400 Studied [yes] vs. Similar [yes] R Parietal Conclusions Observed data FN400 Similar [yes] vs. New [no] Studied [yes] vs. Similar [yes] Parietal

40. Unidimensional and information integration category structures Ashby, Maddox & Bohil (2002) • Categorization experiment • Compared learning of two kinds of category structure • Unidimensional (UD) or rule based • Information integration (II) or “diagonal”

41. COVIS theoryCOmpetition between Verbal and Implicit systems • Proposes distinction between an implicit system that learns categories via a procedural learning mechanism, and a verbal system which learns categories via explicit reasoning and the application of verbal rules • Implicit system learns II structures • Depends upon immediate reward (feedback) • Explicit system learns UD structures • Utilises working memory and does not depend upon immediate feedback

42. Observational vs. Feedback Learning

43. Results

44. E I Conclusions Observed data No. of training trials UD performance Observational vs. feedback learning II performance Inferred structure No. of training trials UD performance Observational vs. feedback learning II performance

45. Questions • Functional dissociations have been used to support or to draw inferences concerning separate underlying mental processes/ functions/ systems • What are the logical foundations of these inferences and are they valid? • Are functional dissociations necessary or sufficient? • What is the form of the alternative (single process) model? • What are the hidden assumptions, if any? • To be continued in Lecture 2

46. References • Glanzer, M. & Cunitz, A. R. (1966). Two storage mechanisms in free recall. Journal of Verbal Learning and Verbal Behavior, 5, 351-360. • Graf, P. & Schacter, D. L. (1985). Implicit and explicit memory for new associations in normal and amnesic subjects. Journal of Experimental Psychology: Learning, Memory, and Cognition, 11(3), 501-518. • Curran, T. (2000). Brain potentials of recollection and familiarity. Memory & Cognition, 28(6), 923-938. • Ashby, F. G., Maddox, W. T. & Bohil, C. J. (2002). Observational versus feedback training in rule-based and information-integration category learning. Memory & Cognition, 30(5), 666-677.