The role of reading span in discourse processing

3.3.3 The role of reading span in discourse processing

  Span and context effects: During reading, inferences must sometimes be drawn; these can be bridging or elaborative (Singer, 1994). The former class are required to make sentences coherent within a passage of text (these inferences were examined by Daneman Carpenter in their seminal 1980 study; see 3.2 Reading Span, p. 55). Elaborative inferences, on the other hand, are those implied by the text but not required for basic understanding. The relative importance of working memory in bridging inferences increases when resources are stretched by the insertion of neutral sentences over which the inference must bridge (Daneman Carpenter, 1980; Guitérrez-Calvo, Castillo Espino, 1996; Singer, Andrusiak, Reisdorf Black, 1992; Singer Ritchot, 1996; Yuill, Oakhill Parkin, 1989). Researchers assume that elaborative inferences are drawn only in the presence of Span and context effects: During reading, inferences must sometimes be drawn; these can be bridging or elaborative (Singer, 1994). The former class are required to make sentences coherent within a passage of text (these inferences were examined by Daneman Carpenter in their seminal 1980 study; see 3.2 Reading Span, p. 55). Elaborative inferences, on the other hand, are those implied by the text but not required for basic understanding. The relative importance of working memory in bridging inferences increases when resources are stretched by the insertion of neutral sentences over which the inference must bridge (Daneman Carpenter, 1980; Guitérrez-Calvo, Castillo Espino, 1996; Singer, Andrusiak, Reisdorf Black, 1992; Singer Ritchot, 1996; Yuill, Oakhill Parkin, 1989). Researchers assume that elaborative inferences are drawn only in the presence of

  Calvo (2001) improved the design and examined predictive inferences 1 , a sub-class

  of elaborative inferences, in an eye-movement tracking study. A Spanish version of the DC RST was used (Guitérrez-Calvo, Jiménez Castillo, 1996). It differed from the original span test in that (i) it was presented on a computer screen and (ii) each participant was required to judge if sentences were factually correct. He confirmed the findings of the Estevez Calvo (2000) study: higher-span readers were faster than lower-span readers in processing sentences that were congruent with their predictive inferences. However, this facilitation did not take place at the target word but further into the target sentence; this suggests that predictive inferences take longer to process (see Calvo, 2001, p. 375 for a detailed interpretation), although it is not accurate to say that processing is truly late because this facilitation represents the end point of building activation. Thus, this provides good evidence that higher-span readers construct inferences to aid on-line sentence processing. As such, it supports the theories of Carpenter and colleagues and MacDonald and colleagues, which postulate (i) DC RST measures general verbal working memory and (ii) it has a role in primary sentence interpretation. SSIR Theory holds that the DC RST does not measure the memory used in on-line processing and, as such, does not predict a difference between higher- and lower-span readers in sentence processing. Furthermore, elaborative inferences may be computed by a nonpsycholinguistic processor.

  Though predictive inferences are mainly associated with higher-span readers, there is some evidence that normal readers (of any capacity) may draw them if context highly constrains their predictability (Calvo Castillo, 1996; Calvo, Castillo Estevez, 1999; Fincher-Kiefer, 1995, 1996; Keefe McDaniel, 1993; Klin, Guzmán Levine, 1999; Klin, Murray, Levine Guzmán, 1999; Murrary, Klin Meyers, 1993; Whitney, Ritchie Crane, 1992). However, some studies have found no evidence of this

  1 For example, given the sentence, She owed a letter to her mother, so she picked up some paper and sat down, a natural predictive inference might be that she wrote a letter (Calvo, 2001, p. 366).

  (Magliano, Baggett, Johnson Graesser, 1993; Millis Graesser, 1994; Potts, Keenan Golding, 1988).

  Van Petten, Weckerly, McIsaac and Kutas (1997) investigated the relationship between reading span and both lexical- and sentential-context effects. The lexical context effect arises from a mutual facilitation between word-pairs such as hot-cold and salt-pepper, as indicated by higher accuracies and shorter reaction times in a number of tasks (e.g. Neely, 1991). The sentential context effect is a similar processing facilitation effect. It is observed when words are presented in coherent rather than incoherent sentences (e.g. Simpson, 1991). For a variety of reasons, theorists have concluded that lexical context effects arise from a fast, automatic route whereas sentence context uses a slow, optional route (e.g. Fodor, 1983; see Van Petten et al., p. 238, for a review). In Van Petten et al.’s ERP study, associated or non-associated words were presented in coherent or non-coherent sentences. Higher-span readers (scoring four or above on the DC RST) showed significantly different processing of sentence-congruent and -incongruent conditions in comparison to lower-span readers (scoring two or below). However, lower-span readers and higher-span readers showed a similar processing difference between associated and non-associated word pairs. Thus, readers with fewer working memory resources are poorer at manipulating sentence-level context information, but may use word-level context to help read a sentence just as well as higher-span readers. The relationship between the DC RST and sentence-level processing is consistent with the theories of Carpenter and colleagues and MacDonald and colleagues; SSIR Theory would predict no such relationship.

  Finally, in a study by Whitney, Ritchie and Clark (1991), participants read passages with vaguely specified referents and actions (e.g. things, do). The overall topic of the passage was obscure (cf. the ‘washing clothes’ passage developed by Bransford Johnson, 1973). Participants provided thinking-out-loud commentaries as they read (see Olson, Duffy Mack, 1984). Lower-span readers tended to provide more elaborations than higher-span readers. Their comments were evenly distributed throughout the passage. Lower-span readers committed to an early interpretation (often incorrect) and tried to force the remaining text to fit this idea. Higher-span readers, on the other hand, tended to save their elaborations for the final moments of the passage. They maintained more cues and delayed their commitment.

  In summary, there is empirical support for the idea that the DC RST taps the same limited resources as on-line elaborative inferential processes. However, it is not clear In summary, there is empirical support for the idea that the DC RST taps the same limited resources as on-line elaborative inferential processes. However, it is not clear

  Text Distance Effects Text distance has been found to affect processing in a number of constructions and

  relations. For example, when a passage contains pronouns, reading time increases in a linear fashion as the number of clauses or sentences intervening between the antecedent and the pronoun increase (Clark Sengul, 1979). Similar effects have been found when entities must be linked according to causality (Keenan, Bailet Brown, 1984), as well as pronominal reference, adverbial reference and connectives (Fischer Glanzer, 1986; Glanzer, Dorfman Kaplan, 1981; Glanzer, Fischer Dorfman, 1984). Such studies are typically interpreted as evidence for the key role of linkages between entities in comprehension (e.g. Just Carpenter, 1980). (The observation that linkage performance varies monotonically with the DC RST (Just Carpenter, 1992) casts doubt on the suggestion that higher-span readers are simply more skilled at marking referents for storage.)

  Though such text distance effects index a working memory capacity, they involve non-initial parsing processes, and they do not in themselves differentiate between the three theories under discussion: for the theory of Carpenter and colleagues, general working memory resources vary; for SSIR Theory, postinterpretive resources can vary; for the connectionist account, distant relations are seen as an ‘irregular’ structure, and, for reasons already outlined, subject to variation due to exposure.

  Lexical ambiguity Another capacity-demanding operation is the processing of ambiguous material. If the

  parser does indeed maintain multiple representations, one would expect lower-span readers to process such ambiguities in a manner different to higher-span readers. Miyake, Just and Carpenter (1994) examined this differential. They presented participants with sentences that contained an ambiguous lexical item (a homograph). Previous studies indicated that both meanings of a homograph are activated immediately, even when the preceding context strongly favours one interpretation (e.g. Seidenberg, Tanenhaus, Leiman Bienkowski, 1982; Swinney, 1979; Tannenhaus, Leiman Seidenberg, 1979). Miyake et al. were interested to observe how readers deal parser does indeed maintain multiple representations, one would expect lower-span readers to process such ambiguities in a manner different to higher-span readers. Miyake, Just and Carpenter (1994) examined this differential. They presented participants with sentences that contained an ambiguous lexical item (a homograph). Previous studies indicated that both meanings of a homograph are activated immediately, even when the preceding context strongly favours one interpretation (e.g. Seidenberg, Tanenhaus, Leiman Bienkowski, 1982; Swinney, 1979; Tannenhaus, Leiman Seidenberg, 1979). Miyake et al. were interested to observe how readers deal

  (22) Since Ken really liked the boxer, he took a bus to the nearest

  sports arena to see the match.

  (23) Since Ken really liked the boxer, he took a bus to the nearest pet

  store to buy the animal.

  In both (22) and (23) the homograph boxer can be interpreted as a pugilist (the

  dominant meaning) or a smooth-coated bulldog (the subordinate meaning) 1 . The reader

  cannot be sure how to resolve the ambiguity until the disambiguating region is encountered (sports arena or pet store). Lower-span readers, with their reduced resources, were expected to ‘lose’ the subordinate meaning quicker because its initial activation level would be lower in the absence of preceding contextual cues (Carpenter Daneman, 1981; Gorfein Bubka, 1989). Thus, the disambiguation that favoured the dominant meaning of boxer would be processed more quickly than the disambiguation that favoured the subordinate meaning. Higher-span readers, on the other hand, should have more resources available for the maintenance of the dominant meaning. They should integrate the disambiguating information with greater facility. The results supported this prediction. Whereas lower- and medium-span readers demonstrate a processing cost upon entering the disambiguating region, higher-span readers do not. This supports the view that the resources measured by the DC RST are involved in the maintenance of multiple lexical representations, which is predicted by the accounts of Carpenter and colleagues and MacDonald and colleagues, but not the SSIR Theory, which holds that the DC RST should not be able to tap the interpretive resource.

  1 Other meanings are: ‘one who puts things in boxes’, ‘a member of a Chinese secret society organized in the late 19th century, whose primary aim was to save the Chinese empire’, ‘a boxwood pegtop’ and ‘a

  tall hat’ (Oxford English Dictionary, 2003).

  Summary

  There is evidence for a relationship between the DC RST and the processing of contextual information in reading. However, conclusions are hampered by two aspects of this evidence: (i) the relationship may be due to simple task overlap, which makes it difficult to evaluate the role of resources, and (ii) the language processes may not reflect initial parsing, which makes it difficult to demarcate between the various resource theories.