Lost on the garden path: Exploring misinterpretation and “good enough” language processing

1. Lost on the garden path: Exploring misinterpretation and “good enough” language processing Kiel Christianson Dept. of Educational Psychology & Beckman Institute

2. Collaborators • Fernanda Ferreira • Carrick Williams • Andrew Hollingworth • Rose Zacks • Tim Slattery • Susan Garnsey • Laura Matzen • RAs in my lab (Kent Lee, Jeong Ah Shin, Ji Kim, Jung Hyun Lim, Heeyoun Cho)

3. So we don’t get lost ourselves,a brief map • What are garden path sentences? • And why are they interesting? • Why worry about interpretation? • And why haven’t other psycholinguists until recently? • Basic data • Christianson, Hollingworth, Halliwell, & Ferreira (2001) • Christianson, Williams, Zacks, & Ferreira (in press) • Recent data • Christianson & Slattery (2005, in prep) • Christianson (still running!) • Some semblance of a conclusion, I hope… • A working definition of “good enough” • Parsing, processing, and interpretation • Implications

4. What relevance to SLA? • Theoretical: Do L2 speakers parse L2 same as L1 speakers do? • Pedagogical: Misinterpretations can be informative wrt mental representations • You don’t know for sure unless you ask!

5. Garden path sentences • Sentences that lead the human sentence processor (HSP) to construct an initial syntactic structure, which turns out to be incorrect, and thus requires syntactic (and semantic) reanalysis.

6. Example While

7. While Anna

8. While Anna dressed

9. While Anna dressed the

10. While Anna dressed the baby

11. While Anna dressed the baby spit

12. While Anna dressed the baby spit up

13. While Anna dressed the baby spit up on

14. While Anna dressed the baby spit up on the

15. While Anna dressed the baby spit up on the bed.

16. While Anna dressed the babyspit up on the bed. • the baby = ambiguous noun phrase (ambiguous region) • spit up = disambiguating verb (disambiguating region)

17. Why use sentences like this? • They induce difficulty and observable slow-downs in processing that is normally smooth and fast • Point is to observe how the system is perturbed, and how it recovers • Not all suffer from “mistakes” • Put the book on the shelf in my backpack.

18. Frazier & Rayner (1982) • The “garden path theory” of syntactic parsing • Eye-tracking used to measure how people read such sentences • Predictable patterns: • Longer fixations (reading times) on disambiguating verb • Regressive eye movements to ambiguous NP and subordinate verb (dressed) • Serial, modular model • one parse at a time, just syntax first • (But this architecture isn’t crucial for assumptions that follow.)

19. Traditional assumptions (no matter what parsing model) • Garden path sentences can be handled one of two ways • Mis-parse is recognized by the HSP, revision is undertaken; if not successful, processor gives up and interpretation is not achieved • Ambiguity/mis-parse isn’t noticed at all; person just keeps reading

20. Questioning traditional assumptions • Does the mis-parse HAVE to be reanalyzed syntactically? • Does the interpretation HAVE to be revised? • Automatic? • MacDonald et al. (1994): There might be situations in which “the communicative goals of the listener can be achieved with only a partial analysis of a sentence, but we view these as degenerate cases” (p. 686). • (An assumption made by proponents of both serial and parallel models of parsing)

21. “Good enough” sentence processing • Ferreira & Henderson (1999); Christianson, et al (2001); Ferreira, Christianson, & Hollingworth (2001); Ferreira, Bailey, & Ferraro (2003); Christianson, et al (in press) • Loosely defined as processing in which the HSP settles for a parse that is in some way incomplete or underspecified, resulting in an interpretation that is not faithful to the input.

22. So why worry about interpretation? “The central problem for future theories of sentence processing is … the development of theories of sentence interpretation.” --Frazier (1998) (Besides, isn’t the whole point of language to derive meaning?)

23. How do we go about studying interpretation? • Traditionally, we don’t. • comprehension question for every 4th sentence or so, just to make sure they’re not zoning out While the man hunted the deer that was brown and graceful ran into the woods. Q: Was the deer brown? OR Was the deer in the woods? Key Q (never asked): Was the man hunting the deer?

24. What happens to the interpretation generated by the initial mis-parse? • Does it linger? • Does it just disappear? • Can it block a full reanalysis? • Can it cause interpretive difficulties even after the rest of the sentence is read?

25. Christianson, Hollingworth, Halliwell, & Ferreira (2001) • What happens to that original, incorrect interpretation derived from the initial, partial, and ultimately incorrect parse? • If syntax (and, it is generally assumed, consequently semantics) fully reanalyzed, it should not influence final interpretation • Major assumption: If interpretation is incorrect, then full reanalysis has not taken place. • Syntactic representation remains incomplete, and thus the interpretation is incorrect • Might be too strong: Maybe syntax OK, semantics never fixed

26. Expt. 1b (1a) While Bill hunted the deer (that was brown and graceful) ran into the woods. (1b) While Bill hunted the deer (that was brown and graceful) paced in the zoo. (implausible) (1c) While Bill hunted the pheasant the deer (that was brown and graceful) ran into the woods. (non-GP)

27. How to judge interpretation? • Radical: Just ask. Q: Did Bill hunt the deer? Yes=INCORRECT No=CORRECT

28. Results Expt. 1b Also gathered confidence ratings; No diff. in any condition in any expt. VERY confident.

29. Expt. 2 • Maybe no reanalysis at all? • Maybe just inference (despite the length of ambiguous region effect in 1b)? (2a) While Bill hunted the brown and graceful deer/the deer that was brown and graceful ran into the woods. (2b) The brown and graceful deer/the deer that was brown and graceful ran into the woods while Bill hunted.

30. Another question, too Did Bill hunt the deer? (subordinate clause question) OR Did the deer run into the woods? (matrix clause question)

31. Expt. 2 results

32. Expt. 3 • So far, baseline inference, but syntactic manipulations push effect around above and beyond inference. • Conclusion: Syntax not fully reanalyzed • Yet…Wouldn’t it be nice to find a syntactic structure that, if fully reanalyzed, would NOT ALLOW THE INFERENCE? • Reflexive absolute transitive (RAT) verbs

33. RAT verbs While Anna dressed the baby that was cute and cuddly spit up on the bed. If fully reanalyzed, Anna CANNOT be dressing the baby; must be dressing HERSELF.

34. Results Expt. 3a-b

35. Conclusion • “Good enough” sentence processing • Syntactic parse not fully reanalyzed • If it is, it’s not mapped onto semantics • Processor happy with incomplete analysis as long as it is plausible. • Likely: “the deer” overtly serves as subject of matrix clause, remains syntactically present as object of subordinate.

36. Older vs. younger readersChristianson, Williams, Zacks & Ferreira (in press, Discourse Processes) • Perhaps misinterpretation effect larger for older readers? • Caused by decrement in inhibitory control in older folks (Hamm & Hasher, 1992; Hasher, Zacks, & May, 1999) • Older readers might even be worse at inhibiting initial incorrect parse.

37. Expt. 1 • OPT verbs Garden path Structure (subordinate-main clause order) • While the man hunted the deer that was brown and graceful ran into the woods. • Non-garden path Structure (main-subordinate clause order) • The deer that was brown and graceful ran into the woods while the man hunted. • Q: Did the man hunt the deer? • RAT: Garden path Structure (subordinate-main clause order) • While Anna dressed the baby that was small and cute played in the crib. • Non-garden path Structure (main-subordinate clause order) • The baby that was small and cute played in the crib while Anna dressed. • Q: Did Anna dress the baby?

38. Results Expt. 1

39. Reading span correlations

40. Expt. 2 • Maybe olders more likely to infer (Hartmann & Hasher, 1991) • OPT verbs allow inference; RAT do not • If so, should see exaggerated effect in plausible conditions for older readers • Also manipulated length of ambiguous region to see if longer-held interpretations harder to inhibit

41. Sentences • Long Ambiguous Region -- Plausible/Implausible • Garden path Structure (subordinate-main clause order) • While the man hunted the deer that was brown and graceful ran into the woods/paced in the zoo. • Non-garden path Structure (main-subordinate clause order) • The deer that was brown and graceful ran into the woods/paced in the zoo while the man hunted. • Short Ambiguous Region -- Plausible/Implausible • Garden path Structure (subordinate-main clause order) • While the man hunted the deer ran into the woods/paced in the zoo. • Non-garden path Structure (main-subordinate clause order) • The deer ran into the woods/paced in the zoo while the man hunted.

42. Results, Expt. 2 • Main effects of ambiguous NP length, plausibility, and age • BUT: • Age did not modulate the effect of plausibility (F1<1; F2<1) nor did it influence the effect of ambiguous NP length (F1<1; F2<1). • As in Expt 1, age didn’t interact with sentence structure, either.

43. Not inhibition or inference • As far as we can tell, anyway • Maybe no inhibition required? Never an alternative full parse/interpretation constructed? • Very “good enough-y” • If inference not the issue either why better at RATs than OPTs? • Maybe they aren’t….

44. Expt. 3 • RAT sentences While Anna dressed the baby that was cute and cuddly spit up on the bed. • Another question: Did Anna dress herself? (Answer should be YES!)

45. Results Expt. 3 (nGP: The baby…spit up…while Anna dressed.)

46. WM correlations with wrong answer rate in Expt. 3

47. Explanation • OPT verbs: Two ways to answer “Did the man hunt the deer?” • Recall verbatim and figure out • Recall propositional content • The man hunted the deer (initial parse) • The man hunted [SOMETHING unspecified] • Congruent with OPT verbs • Olders more likely to rely on “gist” (=propositional) rather than verbatim content

48. RAT • Propositional content • Anna dressed the baby (initial) • Anna dressed [SOMETHING specific] • But what? • Semantics of RAT verbs don’t allow congruency of propositional content • “dress” doesn’t allow unspecified interpretation • In order to get reflexive reading, must reactive syntax to establish government relation and co-indexation

49. WM tie-in • Olders with less WM resources unable to reactivate the syntactic structure required to get the reflexive reading. • Processor may settle on good enough interpretation, but to answer the question, you need more than that • If not enough working memory available to either keep working on structure or recall, recompute, and revise, then stuck.

50. Christianson & Slattery (2005) • No one has ever looked to see if garden paths affect SUBSEQUENT reading • Why should they? Recall traditional assumptions. • If “good enough” processing takes place, should see people moving on to read subsequent text before they’ve completed a full reanalysis.