Network representations of knowledge about chemical equilibrium: Variations with achievement

This study examined variation in the organization of domain-specific knowledge by 50 Year-12 chemistry students and 4 chemistry teachers. The study used nonmetric multidimensional scaling (MDS) and the Pathfinder network-generating algorithm to investigate individual and group differences in student concepts maps about chemical equilibrium. MDS was used to represent the individual maps in two-dimensional space, based on the presence or absence of paired propositional links. The resulting separation between maps reflected degree of hierarchical structure, but also reflected independent measures of student achievement. Pathfinder was then used to produce semantic networks from pooled data from high and low achievement groups using proximity matrices derived from the frequencies of paired concepts. The network constructed from maps of higher achievers (coherence measure = 0.18, linked pairs = 294, and number of subjects = 32) showed greater coherence, more concordance in specific paired links, more important specific conceptual relationships, and greater hierarchical organization than did the network constructed from maps of lower achievers (coherence measure = 0.12, linked pairs = 552, and number of subjects = 22). These differences are interpreted in terms of qualitative variation in knowledge organization by two groups of individuals with different levels of relative expertise (as reflected in achievement scores) concerning the topic of chemical equilibrium. The results suggest that the technique of transforming paired links in concept maps into proximity matrices for input to multivariate analyses provides a suitable methodology for comparing and documenting changes in the organization and structure of conceptual knowledge within and between individual students.     

POLARIZED PRIORITIES OR FLEXIBLE ALTERNATIVES? DIMENSIONALITY IN INGLEHART'S MATERIALISM--POSTMATERIALISM SCALE

Ronald Inglehart's Postmaterialism thesis has undoubtedly beenone of the most influential ideas in cross-national and cross-temporalresearch on political behavior over the past two decades. Thewide-ranging debate and criticism generated by the Inglehartthesis has focused both on theoretical issues concerning thenature of values and on methodological issues concerning themeasurement of Materialism and Postmaterialism, particularlythe method for ranking individual responses. Using a data setthat employed both the original ranking method for measuringvalues and an alternative rating method, we explore the dimensionalstructure of these values and discuss the implications of differencesbetween the two measurement strategies. The two-dimensionalsolution provided by the rating method is, we argue, a moretheoretically appropriate way of understanding Materialist andPostmaterialist values than the notion of a single conflictdimension, since it allows for a more flexible and realisticaccount of the choices made by most social actors—choiceswhich may represent both Materialism and Postmaterialism.     

Memory for Relevant and Irrelevant Information: Evidence for Deficient Inhibitory Processes in Language/ Learning Disabled Children

The present study examined whether language/learning disabled children have greater difficulty than nondisabled children suppressing information that becomes irrelevant during a sentence processing and memory task. During study trials, children were asked to predict and remember the terminal nouns for a series of sentences that highly constrained a terminal noun. For half of the study trials (fillers) the child's prediction was confirmed by presenting the child with the expected ending (e.g., “Butterflies fly by flapping their . . .wings.”). For the remaining study trials (critical trials), however, the sentence ending expected by the child was disconfirmed with a low-probability ending (target noun). Thus, when presented with the sentence, “We made a sandwich with peanut butter and . . . ,” the child's prediction (“jelly”) was disconfirmed with a different ending (“bananas”). Memory for the disconfirmed and target nouns of critical study trials were subsequently tested implicitly with a new sentence-completion task. In this case, memory for disconfirmed and target nouns that had been associated with individual study sentences were measured in terms of priming effects. The analysis of priming effects indicated that language/learning disabled children experienced greater difficulty than nondisabled children inhibiting the activation of irrelevant information (disconfirmed nouns) and sustaining the activation of relevant information (target nouns) during a verbal memory task. These results were discussed in terms of their implications for some of the memory and language difficulties of language/learning disabled children.