Tuesday, November 12, 2013

Sentence processing: The role of memory and expectations in understanding relative clauses

Levy, R., Fedorenko, E., & Gibson, E. (2013). The syntactic complexity of Russian relative clauses. Journal of Memory and Language, 69, 461-495.

Human language is unique amongst communication systems because of its expressivity: We can hear a sentence we have never heard before and understand its meaning. But how does this happen? We do not have the memory resources to pursue every possible interpretation of a sentence, so there must be some sort of cognitive constraint that guides our understanding. Possible cognitive constraints have been investigated by examining how long it takes for people to understand or read sentences that present some confusion, that is, syntactic ambiguity resolution.

Research in processing relative clauses is important in understanding syntactic ambiguity resolution because these are one of the most complex sentence forms we encounter, and they offer an avenue to explore language’s rich expressive capacity. There are two types of relative clauses examined in this paper:

1)   Subject-extracted relative clause
The reporter who attacked the senator hoped for a story
            subject                 relative clause verb        object

2)   Object-extracted relative clause
The reporter who the senator attacked hoped for a story
                 object                                      subject  relative clause verb

The finding is that object relative clause sentences are more difficult to process than subject relative clause sentences. The authors distinguish between two theories that explain this difference in processing: Memory Based Theories and Expectation Based Theories. Memory Based Theories state that the comprehender is actively storing, integrating, and retrieving incoming information from the sentence in an online fashion. In these theories, the more material that needs to be processed, the more overloaded the memory system gets and the higher the processing load. Based on this theory, sentence 2 is harder to process because you need to hold more information in memory before you get to the verb attacked, which is the point where the meaning of the sentence becomes clear.
Expectation Based Theories assume that your previous language experience and semantic content shapes your sentence processing abilities. In fact, for Expectation Based Theories, greater semantic information (more words) in the sentence helps sharpen your expectations and guides your processing, whereas Memory Based Theories would predict that this impairs in processing. Based on this theory, sentence 2 is harder to process because it follows an Object-Subject-Word order. We are used to hearing Subject-Verb-Object orders in English, so this violates our expectations.

Even though the theories were difficult to disentangle in this paper, there are two interesting ideas in this paper: Memory limits may constrain language processing, and language processing may be limited by a lack of language knowledge. Considering which of these resources may be impacting language processing may help to understand a particular individual’s language functioning.

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