Sentence Comprehension
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Human language comprehension takes place whenever a reader or listener processes a language utterance, either in isolation or in the context of a conversation or a text. Many studies of the human language comprehension process have focused on reading of single utterances (sentences) without context. Extensive research has shown, however, that language comprehension is affected also by context preceding a given utterance, as well as many other factors.
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[edit] Ambiguity and Sentence Comprehension Research
Sentence comprehension has to deal with ambiguity in spoken and written utterances, for example lexical, structural, and semantic ambiguities. Ambiguity is ubiquitous, but people usually resolve it so effortlessly that they don't even notice it. For example, the sentence Time flies like an arrow has (at least) the interpretations Time moves as quickly as an arrow, A special kind of fly, called time fly, likes arrows and Measure the speed of flies like you would measure the speed of an arrow. Usually, readers will be only aware of the first interpretation.
Instances of ambiguity can be classified as local or global ambiguities. A sentence is globally ambiguous if it has two distinct interpretations. Examples are sentences like Someone shot the servant of the actress who was on the balcony. (was it the servant or the actress who was on the balcony?) or The cop chased the criminal with a fast car. (did the cop or the criminal have a fast car?). Comprehenders may have a preferential interpretation for either of these cases, but syntactically and semantically, neither of the possible interpretations can be ruled out.
Local ambiguities persist only for a short amount of time as an utterance is heard or writtenand are resolved during the course of the utterance, so that the complete utterance has only one interpretation. Examples include sentences like The critic wrote the interview was enlightening, which is ambiguous when The critic wrote the book has been encountered, but was enlightening remains to be processed. At this point, the sentence could either end, stating that the critic is the author of the book, or it could go on to clarify that the critic wrote something about a book. The ambiguity ends at was enlightening, which determines that the second alternative is correct.
When readers process a local ambiguity, they settle on one of the possible interpretations immediately, without waiting to hear or read more words that might help decide which interpretation is correct (this behaviour is called incremental processing). If they are surprised by the turn the sentence really takes, processing is slowed. This is visible for example in reading times. Locally ambiguous sentences therefore have been used as test cases to investigate the influence of a number of different factors on human sentence processing. If a factor helps readers to avoid difficulty, it is clear that this factor plays a factor in sentence processing.
[edit] Theories about Language Comprehension
Experimental research has spawned a large number of hypotheses about the architecture and mechanisms of sentence comprehension. Issues like modularity versus interactive processing and serial versus parallel computation of analyses have been theoretical divides in the field.
[edit] Architectural Issues
[edit] Modular vs. Interactive
A modular view of sentence processing assumes that each factor involved in sentence processing is computed in its own module, which has limited means of communication with the other modules. For example, syntactic analysis creation takes place without input from semantic analysis or context-dependent information, which are processed separately. A common assumption of modular accounts is a feed-forward architecture, in which the output of one processing step is passed on to the next step without feedback mechanisms that would allow the output of the first module to be corrected. Syntactic processing is usually taken to be the most basic analysis step, which feeds into semantic processing and the inclusion of other information.
Interactive accounts assume that all available information is processed at the same time and can immediately influence the computation of the final analysis.
[edit] Serial vs. Parallel
Serial accounts assume that humans construct only one of the possible interpretations at first, and try another only if the first one turns out to be wrong. Parallel accounts assume the construction of multiple interpretations at the same time. To explain why comprehenders are usually only aware of one possible analysis of what they hear, models can assume that all analyses ranked, and the highest-ranking one is entertained.
[edit] Models
There are a number of influential models of human sentence processing that draw on different combinations of architectural choices.
[edit] Garden Path Model
The Garden Path Model (Frazier 1987) is a serial modular parsing model. It proposes that a single parse is constructed by a syntactic module. Contextual and semantic factors influence processing at a later stage and can induce re-analysis of the syntactic parse. Re-analysis is costly and leads to an observable slowdown in reading. When the parser encounters an ambiguity, it is guided by two principles: Late Closure and Minimal Attachment.
Late Closure causes new words or phrases to be attached to the current clause. For example, "John said he would leave yesterday" would be parsed as John said (he would leave yesterday), and not as John said (he would leave) yesterday (i.e., he spoke yesterday). Minimal Attachment is a strategy of parsimony: The parser builds the simplest syntactic structure possible (that is, the one with the fewest phrasal nodes).
The Garden Path model is no longer a standard explanation for human sentence processing. This is due partly to its strictly serial architecture, while most current models assume at least some degree of early interaction between different factors. Also, its parsing principles have been criticised - for example, the correctness of the predictions made by the Minimal Attachment principle depends on the underlying syntactic representation one assumes. Nonetheless, the Garden Path model has strongly influenced the field for many years.
[edit] Constraint-Based Model
Parallel and interactive
We do generate more than one syntactic analysis, based on evidence provided against Constraint-Based Model:
Garden path sentences seem to refute this: "The florist sent the flowers was very pleased."
Evidence for the Constraint-Based Model: Comprehenders do use their lexical knowledge.
[edit] Findings
[edit] Lexical Preferences
lexical meaning influences sentence comprehension. “she saw her duck and some eggs” is a garden path sentence, makes one think of duck eggs; “She saw her duck and fall down” is different. (Boland 1997). second is slower response time (you have to build two VPs)
[edit] Incomplete or Inaccurate Representations
Christianson et al (2001) asks, Do we construct structural representations of a sentence that are complete and accurate as we parse?
While Anna dressed the baby played in the crib Did the baby play in the crib? (reader response 100%) Did Anna dress the baby? (errors)
Ferreira (2003) People don't immediately read and comprehend a sentence. With active sentences, readers have 100% accuracy. With passive sentences (the man was bitten by the dog, the dog was bitten by the man) had 75% accuracy.
Studies of incomplete representations emphasize the influence of expectations in sentence comprehension.
[edit] References
Carroll, David, The Psychology of Language( Wadsworth Publishing, 2003))
Frazier, Lyn (1987), “Sentence processing: A tutorial review”, in Coltheart, M., Attention and Performance XII: The Psychology of Reading, Lawrence Erlbaum Associates
