Issues and Further Studies

8.1.2 Issues and Further Studies

  This thesis has been concerned with individual differences. The potential for a design to capture these differences will depend on its treatment of variability. With regards to the reading span measure, this means (i) measure reading span and many other variables, then look for correlations (e.g. Daneman Merikle, 1996), (ii) break the sample in half by span and compare the halves (e.g. Mendelsohn Pearlmutter, 1999), (iii) compare the extremes of the span distribution and ignore those data towards the centre (e.g. MacDonald, Just Carpenter, 1992).

  The methodology proposed by (i), the correlational approach, requires a large number of participants in order to obtain the necessary variation. In this way, researchers can determine the relationships between a large number of variables. This The methodology proposed by (i), the correlational approach, requires a large number of participants in order to obtain the necessary variation. In this way, researchers can determine the relationships between a large number of variables. This

  The second methodology, which, like the third, is a true individual differences approach, risks becoming arbitrary. The dividing line between higher- and lower-span readers may be moved and, with this, the pattern of results may change. At present there is no standard threshold (though Mendelsohn Pearlmutter’s, 1999, span level of four is typical). This also invites the problem of unequal group sizes because lower-span readers constitute a majority in most populations (Daneman Merikle, 1996).

  The third approach is to examine the extremes of the reading span population. Participants are divided into three groups: low, medium and high. The membership criteria vary somewhat (e.g. King Just, 1991, classified higher-spans as ≥ 4.5 and lower-spans as ≤ 2.5, while van Petten, Weckerly, McIsaac Kutas, 1997, classified them as ≥ 4 and ≤ 2). Without a scatterplot that suggests a grouping of the data, the criteria can risk being arbitrary. Furthermore, (i) an examination of the extremes can artificially inflate differences, and (ii) ignoring the medium-span group will abandon a significant proportion of the sample’s natural variability. Additionally, if a researcher wishes to accrue two equally-sized higher- and lower-span groups (e.g. Calvo, 2001),

  the time investment will quickly spiral 1 . In this thesis, the view was taken that the two individual differences approach suffer problems that the correlational approach does not. It may be suggested that participants were not tested in sufficient quantity for the correlation approach to work. While this criticism cannot be countered directly, we can be sure that strong individual differences in attachment preference were consistently found for the RC-attachment ambiguity; enough material for the reading span test to work on.

  What may underlie individual differences? Reliable individual differences in attachment preference were found in two of the three

  studies in this thesis (see pp. 105 and 131). The question remains, therefore, as to the cause of these differences. On the basis of these data, the answer must be that reading

  1 The studies in this thesis are a reported for an undergraduate population but the lower-span readers still greatly outnumbered the higher-span readers (see pp. 105, 128, and 179).

  span (as measured by the DC RST and the WC RST) is unlikely to be a component of RC-attachment. The other hypotheses that have been suggested remain: notably Tuning (Cuetos, Mitchell Corley, 1996) and Multiple Constraint Satisfaction (MacDonald, Pearlmutter Seidenberg, 1994).

  However, both hypotheses would accommodate memory variation with ease. For Tuning, this would involve varying the breadth and depth (‘grain’, see p. 43) of its statistical database. For MCS, this would stem from the Frequency by Regularity interaction, where greater experience breeds irregular mapping strategies for different structures. Bearing in mind previous comments, though the failures to demonstrate reading span and attachment interactions make a role for verbal working memory unlikely, it is possible that the reading span tests may be improved to the extent that the relationship becomes identifiable. For this reason, future research should concentrate on refining all aspects of the reading span tests.

  Examining a different ambiguity As discussed, a crucial Span by Clause Type by Region interaction had been found for

  the MVRR ambiguity (MacDonald, Just Carpenter, 1992; Pearlmutter MacDonald, 1995). This interaction is explicitly predicted by the single resource theories of Carpenter and colleagues and MacDonald and colleagues. While the interaction may yet be the result of readers who are mysteriously ‘better’ or ‘worse’ than one another, it is possible that the TA MVRR elicited a span effect because it is more difficult to process than a GA RC (the latter was selected because of the individual differences already documented for the ambiguity); as processing load increases, differences in span should be exaggerated. For this reason, a further study that combines the more refined WC RST and the MVRR is indicated.

  The reading span task in theory The existence of a relationship between reading span and parsing is still not certain. I

  would like to argue that the modifications (both of design and analysis) of the studies in this thesis make the existence of this relationship less likely. It may not speak directly to the question of memory and its relation to parsing because this thesis (and current research) rests heavily on the reading span test. Though many studies have investigated the relationship between reading span and various cognitive abilities, evidence is sufficiently various to support the position of the Single Resource Theory, Separate

  Sentence Integration Resource Theory or the Connectionist Account; on balance it should be concluded that the evidence is suggestive but weak.

  One aim for research should, therefore, be the refinement of what we mean by ‘reading span’ and the extent to which it is synonymous with verbal working memory. This will require the selection and test of hypotheses that are as specific as possible, such as those in the final, on-line study in this thesis. Correlational studies that chart covariance are not specific enough. However, since it must be said that there is already

  a wealth of literature on reading span (e.g. Daneman Merikle, 1996) and it must equally be said that we still don’t know exactly what reading span measures, this aim may only be achieved through creative theorizing as to its basis: theories must be specific enough to falsified (to the extent permitted by resource accounts, which can be inherently vacuous; Navon, 1984). More specifically, studies that examine span and parsing will need to demonstrate statistical interactions that exhaust all criticisms (as King Just’s 1991 findings do not).

  Additionally, future research should converge on a standard division between high span reader and low span readers. This will aid comparison.

  The reading span task in practice Comments have already been made on the most common reading span test, the DC RST

  (see 5.1.2 Methodological issues, p. 120): (i) it yields a measure of storage alone, where storage and processing are of equal interest; it fails to control for (ii) lexical variables or (iii) depth processing during the reading component; (iv) it employs a ‘hurdle’ method of marking, where a concentration lapse at an early level may result in an incorrect, low span score. In the same passage, in Chapter Five, it was noted that the WC RST significantly improves upon the DC RST. However, the DC RST remains the standard test even in very recent papers (e.g. Vos et al., 2001; and cf. the meta-analysis by Daneman Merikle, 1996). The improvements on the DC RST by the WC RST make theoretical sense and the empirical improvements have been quantified thoroughly (see Waters Caplan, 1996b). Further research may be best served by capitalizing on these improvements.

  On a more informal note, it became clear to me that participants developed ad hoc strategies during the reading span test (both versions). The test is stressful, lengthy, and participants are aware that it will only get harder. For some, the challenge is relished; for others, the reaction is horror. While extreme reactions were rare, it can argued that On a more informal note, it became clear to me that participants developed ad hoc strategies during the reading span test (both versions). The test is stressful, lengthy, and participants are aware that it will only get harder. For some, the challenge is relished; for others, the reaction is horror. While extreme reactions were rare, it can argued that

  But the difficulties remain: What is verbal working memory? What information does it store? Does it process and hold its own representations, or are they harvested from other processes? Critics would argue that one cannot measure reading span without at first defining it. There is no straight answer to this. An intelligence test is another example of such pragmatic assessment. The DC RST is psychometrics in reverse: it survived and propagated in the literature because it correlated with measures of comprehension. But its eminence in the literature and, particularly, its role in the parsing of the MVRR ambiguity (Just Carpenter, 1992), suggests that the reading span test should not be dismissed, blunt instrument though it may be.