Individual differences in parsing

2.4.2 Individual differences in parsing

  Evidence for individual variability in parsing is difficult to disregard. Cross-linguistic difference data paves the way for such variability. Evidence in support of the Linguistic Tuning Hypothesis (e.g. Cuetos, Mitchell, Brysbaert Corley, 1996; Mitchell, 1994; Garcia-Orza and Santos, 1999; Desmet, Brysbaert and De Baecke, 2002) supports exposure as a basis for variability. Evidence comes from other domains. For example, handedness can affect the efficiency of sentence processing: dextral (right-handed) adults have been shown to be faster at syntactic processing than sinistral (left-handed) adults, who tend to focus more on words and meaning (Townsend, Carrithers Bever, 2001). Children show individual differences in syntactic awareness (Plaza Touzin, 2002) and verb use (Thordardottir Weismer, 2001). Kemper (1987) analyzed the occurrence of different types of embedded clauses in both a longitudinal and cohort- sequential sample of adult writing taken from diaries. She found that overall complexity of writing declined across the life-span. Adults aged 70 and above produced few sentences with embedded clauses, especially left-branching embeddings. Other studies provide support for the influence of age on verbal fluency (Hultsch, Hertzog, Small, McDonald-Miszczak Dixon, 1992; Lindenberger, Mayr Kliegl, 1993; McCrae, Arenberg Costa, 1987; Salthouse, 1993). Working memory constraints associated with Alzheimer’s disease impair the ability to process discourse in on-line tasks (Almor, MacDonald, Kempler, Andersen Tyler, 2001).

  With the exception of one illustrative example (below), we will examine individual differences further in the third chapter, once we have discussed a mechanism that may account for individual differences: memory.

  Individual Preferences for a Structure in Adults One of the clearest indications of individual variation comes from Corley (1995).

  Participants were administered an off-line questionnaire with items counterbalanced for order (of NPs 1 and 2) and word number. Sentences were initial fragments and took the form:

  (20) The court heard about the investigator(s) of the murder(s)

  WH_____ W_____

  Following each item, participants were required to complete the sentence using either of the two relative pronouns who or which, followed by was or were. The choice of pronoun or verb indicated attachment preference. Overall, there was great variability in choice of attachment site (0-100 for each). More interestingly, participants were tested again three weeks later. Items appeared thus:

  (21) The court head about the murder(s) of the investigator(s)

  WH_____ W_____

  Item (21) is a follow-up variant of (20). The correlation between site preference in

  the first and second matched questionnaires was very high (r 50 = 0.799, p < 0.001).

  This individual structural preference provides evidence against Construal Theory because, even with the inherent variability of non-primary RC computations, this variability is language-wide. Equally, it raises problems for any theory that does not posit an additional factor that might vary between individuals. This includes all theories so far, with the exception of MCS accounts, which explicitly hypothesize variability in the processing of probabilistic information (e.g. MacDonald, Just Carpenter, 1992; Just Carpenter, 1992; Pearlmutter MacDonald, 1995).

  However, this conclusion has shortcomings. Using an off-line questionnaire is problematic in terms of its sensitivity to initial parsing preferences. Another aspect of concern is the production element of the study (see 2.3.2 Delayed Access Techniques, p. 29). Participants were required to produce their responses, making the questionnaire a measurement of production biases rather than comprehension. Of course, it is reasonable to assume that the comprehending parser and its companion in production will operate in substantially similar ways regarding their treatment of syntax. But it may still be the case that individual preferences (and variation) in this assignment result from However, this conclusion has shortcomings. Using an off-line questionnaire is problematic in terms of its sensitivity to initial parsing preferences. Another aspect of concern is the production element of the study (see 2.3.2 Delayed Access Techniques, p. 29). Participants were required to produce their responses, making the questionnaire a measurement of production biases rather than comprehension. Of course, it is reasonable to assume that the comprehending parser and its companion in production will operate in substantially similar ways regarding their treatment of syntax. But it may still be the case that individual preferences (and variation) in this assignment result from

  Chapter Summary

  We began this chapter with an outline of the thesis as a whole: an investigation of parsing theories from the standpoint of individual variation. The thesis is particularly concerned with theoretical ideas that might underlie this variation. A pragmatic definition of language was proposed along with a rudimentary parser in 2.2.2 What is Parsing?, p. 18. The chapter went on to justify, for the purposes of experimental work, the separation of syntax and semantics (2.2.3 Separating Syntax and Semantics, p. 19), comprehension and production (2.2.4 Separating Production and Comprehension, p. 20), and writing and speaking (2.2.5 Separating Writing and Speaking, p. 21). We then turned to examine the use of ambiguous sentences with several methodologies: ERP studies, eye-movement tracking and self-paced reading (2.3.1 Immediate Access Techniques, p. 26), and tick-box and sentence completion questionnaires (2.3.2 Delayed Access Techniques, p. 29).

  The next section was concerned with types of parser. These are: serial parsers that may proceed deterministically or probabilistically; delayed attachment parsers; parallel parsers that develop unweighted, ranked or weighted representations (2.3 Classes of Parsing Models, p. 32). Our review of the evidence, which included the results of cross- linguistic studies, concluded, tentatively, that weighted parallel models find the most empirical support, though both types of serial parser have yet to be falsified conclusively (2.3.5 Evidence, p. 38).

  The chapter concluded with the introduction of some individual differences in RC attachment and suggested that a MCS-based theory, coupled with a working memory component, is the parsing theory most compatible with such individual differences (2.4.2 Individual differences in parsing, p. 49).