Glenda Andrews

Separating Cognitive Capacity from Knowledge: A New Hypothesis

We propose that working memory and reasoning share related capacity limits. These limits are quantified in terms of the number of items that can be kept active in working memory, and the number of interrelationships between elements that can be kept active in reasoning. The latter defines the complexity of reasoning problems and the processing loads they impose. Principled procedures for measuring, controlling or limiting recoding and other strategies for reducing memory and processing loads have opened up new research opportunities, and yielded orderly quantification of capacity limits in both memory and reasoning. We argue that both types of limit might be based on the limited ability to form and preserve bindings between elements in memory.

Preschool Home Literacy Practices and Children's Literacy Development: A Longitudinal Analysis.

In this 3-year longitudinal study, the authors tested and extended M. Senechal and J. Le Fevres (2002) model of the relationships between preschool home literacy practices and childrens literacy and language development. Parent-child reading (Home Literacy Environment Questionnaire plus a childrens Title Recognition Test) and parental teaching of letters, words, and name writing were assessed 6 months prior to childrens school entry. The 143 children (55% male participants; mean age = 5.36 years, SD = 0.29) attended Gold Coast, Australia government preschools. Parent-child reading and literacy teaching were only weakly correlated (r = .18) and were related to different outcomes consistent with the original model. Age, gender, memory, and nonverbal ability were controlled. Parental teaching was independently related to R. W. Woodcocks (1997) preschool Letter-Word Identification scores (R²change = 4.58%, p = .008). This relationship then mediated the relationships between parental teaching and Grades 1 and 2 letter-word identification, single-word reading and spelling rates, and phonological awareness (rhyme detection and phonological deletion). Parent-child reading was independently related to Grade 1 vocabulary (R²change = 5.6%, p = .005). Thus, both home practices are relevant but to different aspects of literacy and language development.

A Cognitive Complexity Metric Applied to Cognitive Development.

Two experiments tested predictions from a theory in which processing load depends on relational complexity (RC), the number of variables related in a single decision. Tasks from six domains (transitivity, hierarchical classification, class inclusion, cardinality, relative-clause sentence comprehension, and hypothesis testing) were administered to children aged 3-8 years. Complexity analyses indicated that the domains entailed ternary relations (three variables). Simpler binary-relation (two variables) items were included for each domain. Thus RC was manipulated with other factors tightly controlled. Results indicated that (i) ternary-relation items were more difficult than comparable binary-relation items, (ii) the RC manipulation was sensitive to age-related changes, (iii) ternary relations were processed at a median age of 5 years, (iv) cross-task correlations were positive, with all tasks loading on a single factor (RC), (v) RC factor scores accounted for 80% (88%) of age-related variance in fluid intelligence (compositionality of sets), (vi) binary- and ternary-relation items formed separate complexity classes, and (vii) the RC approach to defining cognitive complexity is applicable to different content domains.

Theory of mind and relational complexity.

Cognitive complexity and control theory and relational complexity theory attribute developmental changes in theory of mind (TOM) to complexity. In 3 studies, 3-, 4-, and 5-year-olds performed TOM tasks (false belief, appearance-reality), less complex connections (Level 1 perspective-taking) tasks, and transformations tasks (understanding the effects of location changes and colored filters) with content similar to TOM. There were also predictor tasks at binary-relational and ternary-relational complexity levels, with different content. Consistent with complexity theories: (a) connections and transformations were easier and mastered earlier than TOM; (b) predictor tasks accounted for more than 80% of age-related variance in TOM; and (c) ternary-relational items accounted for TOM variance, before and after controlling for age and binary-relational items. Prediction did not require hierarchically structured predictor tasks.

Measuring the Influence of Complexity on Relational Reasoning: The Development of the Latin Square Task

Relational complexity (RC) theory conceptualizes an individual’s processing capacity and a task’s complexity along a common ordinal metric. The authors describe the development of the Latin Square Task (LST) that assesses the influence of RC on reasoning. The LST minimizes the role of knowledge and storage capacity and thus refines the identification of a processing-capacity-related complexity effect in task performance. The LST is novel with one explicit rule that is easily understood by adults and children. In two studies, a test of 18 items encompassing three RC levels was administered to university (N = 73; 16-33 years) and school (N = 204; 8-19 years) students. Rasch analyses indicate that the LST scores were psychometrically stable across age groups and provides important diagnostic clues for task development. Consistent with RC theory, the LST is sensitive to parallel and serial (via segmentation) processing demands. The LST provides a strong basis for research on working memory and related constructs (fluid intelligence).

Relational processing and working memory capacity in comprehension of relative clause sentences

Previous research has indicated that the cognitive load imposed by tasks in various content domains increases with the complexity of the relational information processed. Sentence comprehension entails processing noun-verb relations to determinewho did what to whom. The difficulty of object-extracted relative clause sentences might stem from the complex noun-verb relations they entail. Across three studies, participants read 16 types of object- and subject-extracted relative clause sentences at their own pace and then responded to a comprehension question for each sentence. Relational processing was assessed using a premise integration task or a Latin square task. These tasks predicted comprehension of object-relatives before and after controlling for subject-relatives. Working memory (WM) capacity was assessed using reading span or forward and backward digit span tests. WM tasks predicted comprehension of object-relatives before but not after controlling for subject-relatives. Comprehension of object-relatives relied more heavily on a domain-general capacity to process complex relations than on WM capacity.

Using postoperative cardiac Troponin-I (cTi) levels to detect myocardial ischaemia in patients undergoing vascular surgery

BACKGROUND Cardiac complications occur commonly in vascular surgery patients. Diagnosis of cardiac complications is difficult because of the inaccuracies associated with traditional cardiac enzyme measurements. CTi, a highly sensitive and specific marker of myocardial injury, may be able to detect cardiac complications with greater ease and accuracy. METHODS The study prospectively examined 100 consecutive patients who underwent major vascular surgery between 6/7/98 and 31/12/98 at the Royal Brisbane Hospital. Daily measurements of cTi, creatine kinase (CK), creatine kinase MB (CKMB), CKMB index, renal function and haemoglobin were taken for three postoperative days. One postoperative electrocardiograph (ECG) was taken. An extensive cardiac history was taken. Intraoperative and postoperative events were recorded. FINDINGS There were 100 patients. 18 patients (18%) had a cTi elevation. On the basis of classical diagnostic criteria, 15 patients (15%) suffered one or more cardiac complication (either myocardial infarction, congestive cardiac failure, unstable angina or atrial fibrillation). One patient (1%) who had a cTi elevation died. CTi elevation occurred in five patients (5%) who were not diagnosed with cardiac complications based on traditional criteria. Despite not meeting specific diagnostic criteria for cardiac complications, all patients showed signs and symptoms that could be attributed to myocardial ischaemia. Every patient who developed congestive cardiac failure or atrial fibrillation had a cTi elevation. A Chi-square analysis revealed a significant association between cTi elevation and postoperative cardiac complications. Four variables contributed small but significant amounts of unique variance to the prediction of peak cTi on linear regression analysis. These were peak CKMB index, postoperative congestive cardiac failure, postoperative chest pain and postoperative cardiac complications. CONCLUSIONS Routine cTi monitoring of postoperative vascular patients would be an effective and inexpensive way to detect patients with cardiac complications. The relationship between postoperative cTi elevation and significant coronary artery disease remains to be shown.

: The development of deductive reasoning: How important is complexity?

Current conceptions of the nature of human reasoning make it no longer tenable to assess childrens inference by reference to the norms of logical inference. Alternatively, the complexity of the mental models employed in childrens inferences can be analysed. This approach is applied to transitive inference, class inclusion, categorical induction, theory of mind, oddity, categorical syllogisms, analogy, and reasoning deficits. It is argued that a coherent account of childrens reasoning emerges in that there is correspondence between tasks at the same level of complexity across different domains, and that the inferences of younger children, while impressive and important, are consistently simpler than those of older children.

Genetic Basis of a Cognitive Complexity Metric

Relational complexity (RC) is a metric reflecting capacity limitation in relational processing. It plays a crucial role in higher cognitive processes and is an endophenotype for several disorders. However, the genetic underpinnings of complex relational processing have not been investigated. Using the classical twin model, we estimated the heritability of RC and genetic overlap with intelligence (IQ), reasoning, and working memory in a twin and sibling sample aged 15-29 years (N = 787). Further, in an exploratory search for genetic loci contributing to RC, we examined associated genetic markers and genes in our Discovery sample and selected loci for replication in four independent samples (ALSPAC, LBC1936, NTR, NCNG), followed by meta-analysis (N>6500) at the single marker level. Twin modelling showed RC is highly heritable (67%), has considerable genetic overlap with IQ (59%), and is a major component of genetic covariation between reasoning and working memory (72%). At the molecular level, we found preliminary support for four single-marker loci (one in the gene DGKB), and at a gene-based level for the NPS gene, having influence on cognition. These results indicate that genetic sources influencing relational processing are a key component of the genetic architecture of broader cognitive abilities. Further, they suggest a genetic cascade, whereby genetic factors influencing capacity limitation in relational processing have a flow-on effect to more complex cognitive traits, including reasoning and working memory, and ultimately, IQ.

Development of Relational Processing in Hot and Cool Tasks

The research investigated the role of complexity and the hot–cool distinction in cognitive development. The 120, 3- to 6-year-old children completed four hot tasks, which involved an affective component and three cool tasks, which did not. All tasks included binary- and ternary-relational items. Complexity was a major source of difficulty on all tasks, especially for younger children. Consistent with a hot–cool distinction, ternary-relational processing emerged earlier and more 4- and 5-year-olds mastered ternary-relational items in hot than cool tasks. Overall performance was better in hot than cool tasks at 4 years but this pattern was reversed at 6 years.