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Lost on the garden path: Exploring misinterpretation and “good enough” language processing Kiel Christianson Dept. of Educational Psychology & Beckman Institute 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) So we don’t get lost ourselves, a brief map 1. What are garden path sentences? And why are they interesting? 2. Why worry about interpretation? And why haven’t other psycholinguists until recently? 3. Basic data Christianson, Hollingworth, Halliwell, & Ferreira (2001) Christianson, Williams, Zacks, & Ferreira (in press) 4. Recent data Christianson & Slattery (2005, in prep) Christianson (still running!) 5. Some semblance of a conclusion, I hope… A working definition of “good enough” Parsing, processing, and interpretation Implications 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! 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. Example While While Anna While Anna dressed While Anna dressed the While Anna dressed the baby While Anna dressed the baby spit While Anna dressed the baby spit up While Anna dressed the baby spit up on While Anna dressed the baby spit up on the While Anna dressed the baby spit up on the bed. While Anna dressed the baby spit up on the bed. the baby = ambiguous noun phrase (ambiguous region) spit up = disambiguating verb (disambiguating region) 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. 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.) Traditional assumptions (no matter what parsing model) Garden path sentences can be handled one of two ways 1. Mis-parse is recognized by the HSP, revision is undertaken; if not successful, processor gives up and interpretation is not achieved 2. Ambiguity/mis-parse isn’t noticed at all; person just keeps reading 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) “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. 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?) 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? 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? 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 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) How to judge interpretation? Radical: Just ask. Q: Did Bill hunt the deer? Yes=INCORRECT No=CORRECT Results Expt. 1b Also gathered confidence ratings; No diff. in any condition in any expt. VERY confident. 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. Another question, too Did Bill hunt the deer? (subordinate clause question) OR Did the deer run into the woods? (matrix clause question) Expt. 2 results 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 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. Results Expt. 3a-b 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. Older vs. younger readers Christianson, 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. 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? Results Expt. 1 Reading span correlations 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 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. 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. 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…. 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!) Results Expt. 3 (nGP: The baby…spit up…while Anna dressed.) WM correlations with wrong answer rate in Expt. 3 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 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 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. 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. Method Context AFTER garden path sentence (eye-tracking) opening region S1 | ambiguous NP1 region While the man hunted(,) | the deer that was | disambiguation large and brown | ran into the woods. opening region S2 | NP2 region The man was hunting | a deer (bear) in the woods. Results Clear classic GP effects – First pass time ME of struct. on NP1; 72ms longer when non-GP ME of struct. on disambiguation; 56ms longer when GP ME of NP2 on NP2; 158ms longer when mismatched New Results Go Past time (includes re-fixations after leftward regressions) – ME of struct. on disambiguation; 264ms longer when GP – ME of struct. on NP2; 86ms longer when GP – ME of NP2 on NP2; 248ms longer when mismatched – Marg. ME (p = .081) by P of struct. on S2 opening region Summary Robust GP effects in early and late measures Clear indication that readers moved on to S2 before structural work on S1 was completed Lack of interaction suggests that processes related to structural revision and lexical content are separate. S1 ambiguity lingers into S2 & amplified by NP2, irrespective of match. What is “good enough” processing? NOT “shallow” parsing – In other words, not just lack of effort – Confidence ratings; downstream effects of GP structure Results in SOME kind of underspecified representation – Which representation (syntax, semantics, both, other)? Underspecification likely result of Incomplete Processing (=good enough) – Interpretation formed before all sources of information are available (some sources slowed by computational demands) – Processor moves on (even if some processes are still running) Christianson (in preparation) Change detection paradigm (Sanford, et al., 2005) – Memory for text based on representation constructed for it. – Changes to text that are consistent with representation should be harder to detect. The cookout was going well so far. While Tom grilled the hot dog that was long and fatty began to burn. The burgers sure looked good, though. The cookout was going well so far. While Tom grilled the hot dog that was long and fatty it began to burn. The burgers sure looked good, though. Conditions Garden path vs. non-garden path (comma) – While Tom grilled, the hot dog that was long and fatty began to burn. NP-it vs. it-NP – While Tom grilled it the hot dog that was long and fatty began to burn. Results, Expt. 1 Sig. ME of structure & order; Sig. INTERACTION Summary People more sensitive to changes in GP sentences – NOT “shallow” processing; processor notices the ambiguity – Change acts like question in Christianson, et al (in press) and NP2 in Christianson & Slattery Spurs processor to resolve lingering structural problem by some means, because that information becomes critical for interpretive task However, significant interaction (p = .018) suggests that in GP condition, sometimes the partial reanalysis proposed by Christianson et al (2001) DOES take place – Two “hot dogs” in representation, congruent with addition of “it” in DO position of subordinate clause Conclusion Good enough processing results in interpretations not faithful to the content – Not previously noticed by researchers because right questions not asked – Not usually noticed by people because usually not critical for integration of later material (often even incorrect interpretation can be plausibly maintained in context) Good enough, not just shallow – Processor actively tries to resolve, but may move on because resources are limited, and input is not – (The “Life is short!” model of sentence processing) Implications (psycholinguistic) Suggests different mechanisms for parser and processor – Parser worried about getting a licit syntactic structure (but might truncate the parse, too) – Processor worried about getting a plausible, contextually consistent interpretation – Parser might be slowed down by ambiguities – Processor might run ahead and not check final parse unless underspecified representation results in an interpretation that doesn’t fit in context Implications (general) Extent to which parser keeps working or processor can look back at results probably depends on STM capacity STM or other individual differences likely predictive of eventual interpretation accuracy Over-reliance of processor on top-down (semantic, discourse) information (perhaps compensatory) might accentuate misinterpretations (whether it affects syntactic parse or not) – Older readers, L2 readers, struggling readers, young readers Good enough usually good enough, but not always. Misinterpretations informative for theorists – can be predicted and manipulated consistently enough to be exploited in reading research and instruction (e.g., to increase meta- linguistic awareness) Thank you!
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