The selective impact of question form and input mode on the symbolic distance effect in children

Five experiments are reported on the symbolic distance effect (SDE) and related phenomena with 6- and 9-year-old children. In the first of these, children were asked to judge the relative sizes of animals in verbal and pictorial tests featuring the comparatives "bigger" and "smaller." A perceptual condition with actual objects was included by way of comparison. A Symbolic Distance Effect was obtained for both lexical and pictorial input. Mode differences were also observed. Pictures produced faster responses than words, and congruity effects occurred only in the pictorial condition. Although performance was similar in tests with either comparative, our subsequent experiments on both 6- and 9-year-olds reveal a significant asymmetry in the child's capacity to verify statements of relation as a function of the direction along the (size) continuum implied by the question. However, important differences between age groups also apparent in the data lead us to conclude that the older subjects develop strategies to overcome this asymmetry by translating certain statements of relation into a form more congruent with their natural modes of encoding.     

Group aggregates and individual reliability: The case of verbal short-term memory

Two experiments examined the generalizability of the effects of word length and phonological similarity with visual and auditory presentation in immediate verbal serial ordered recall. In Experiment 1, data were collected from 251 adult volunteers drawn from a broad cross-section of the normal population. Word length and phonological similarity in both presentation modes significantly influenced the group means. However, 43% of the subjects failed to show at least one of the effects, and the likelihood that effects appeared was highly correlated with verbal memory span. In Experiment 2, 40 subjects of the original sample were retested, 20 of whom had failed to show one or more effects in Experiment 1. Whether or not an effect had appeared for individual subjects on the first test session was a poor predictor of whether the effect would appear on retest. Finally, an analysis of subject reports demonstrated that the patterns of experimental data could be accounted for in part by the strategies that subjects reported using, and the effect of strategy was independent of the effect of span. The implications of these findings for theories of verbal short-term memory are discussed.     

Stressful life events: Their past and present status

The present paper reviews some of the major fields of interest in current life event research. Some theoretical issues are examined: for example, generality versus specificity of life event effects, the time span encompassed by life event research, development of life change scales, and perceptual concensus concerning the severity of life changes. Methodological problems concerned with causal or correlational conclusions and illness behaviour are also discussed. Models of the life event stress process are mentioned with reference to ‘resistance resources’. Finally the field of life event research has been integrated into McGrath’s conceptualization of stress research.     

A note on computing Louis’ observed information matrix identity for IRT and cognitive diagnostic models

Using Louis’ formula, it is possible to obtain the observed information matrix and the corresponding large-sample standard error estimates after the expectation–maximization (EM) algorithm has converged. However, Louis’ formula is commonly de-emphasized due to its relatively complex integration representation, particularly when studying latent variable models. This paper provides a holistic overview that demonstrates how Louis’ formula can be applied efficiently to item response theory (IRT) models and other popular latent variable models, such as cognitive diagnostic models (CDMs). After presenting the algebraic components required for Louis’ formula, two real data analyses, with accompanying numerical illustrations, are presented. Next, a Monte Carlo simulation is presented to compare the computational efficiency of Louis’ formula with previously existing methods. Results from these presentations suggest that Louis’ formula should be adopted as a standard method when computing the observed information matrix for IRT models and CDMs fitted with the EM algorithm due to its computational efficiency and flexibility.     

Dual processes in recognition: Does a focus on measurement operations provide a sufficient foundation?

Current theoretical thinking about dual processes in recognition relies heavily on the measurement operations embodied within the process dissociation procedure. We critically evaluate the ability of this procedure to support this theoretical enterprise. We show that there are alternative processes that would produce a rough invariance in familiarity (a key prediction of the dual-processing approach) and that the process dissociation procedure does not have the power to differentiate between these alternative possibilities. We also show that attempts to relate parameters estimated by the process dissociation procedure to subjective reports (remember-know judgments) cannot differentiate between alternative dual-processing models and that there are problems with some of the historical evidence and with obtaining converging evidence. Our conclusion is that more specific theories incorporating ideas about representation and process are required.     

A Comparison of Single and Multi-Test Working Memory Assessments in Predicting Academic Achievement in Children

Children assessed as having low working memory capacity have also been shown to perform more poorly than their same-aged peers in measures of academic achievement. Early detection of working memory problems is, therefore, an important first step in reducing the impact of a working memory deficit on the development of academic skills. In this study, we compared a single-test assessment, the Working Memory Power Test for Children (WMPT) and a multi-test assessment, the Automated Working Memory Assessment (AWMA), in their ability to predict academic achievement in reading, numeracy, and spelling. A total of 132 Australian school children (mean age 9 years, 9 months) participated in the research. Strong positive correlations between the WMPT and AWMA total scores were found, indicating good convergent validity of the single and multi-test measures. WMPT scores correlated with each of the four AWMA subtests designed to assess verbal and visuospatial short-term and working memory. WMPT and AWMA scores separately predicted performance on Word Reading, Numerical Operations, and Spelling. Compared with either measure alone, the WMPT and the AWMA in combination predicted more of the variance in Word Reading and Numerical Operations, but not in Spelling. Theoretical and practical implications of these findings are discussed.