Panning for the gold in health research: Incorporating studies’ methodological quality in meta-analysis

Background: Systematic reviews now routinely assess methodological quality to gauge the validity of the included studies and of the synthesis as a whole. Although trends from higher quality studies should be clearer, it is uncertain how often meta-analyses incorporate methodological quality in models of study results either as predictors, or, more interestingly, in interactions with theoretical moderators.

Objective and methods: We survey 200 meta-analyses in three health promotion domains to examine when and how meta-analyses incorporate methodological quality.

Results: Although methodological quality assessments commonly appear in contemporary meta-analyses (usually as scales), they are rarely incorporated in analyses, and still more rarely analysed in interaction with theoretical determinants of the success of health promotions. The few meta-analyses (2.5%) that did include such an interaction analysis showed that moderator results remained significant in higher quality studies or were present only among higher quality studies. We describe how to model quality interactively with theoretically derived moderators and discuss strengths and weaknesses of this approach and in relation to current meta-analytic practice.

Conclusions: In large literatures exhibiting heterogeneous effects, meta-analyses can incorporate methodological quality and generate conclusions that enable greater confidence not only about the substantive phenomenon but also about the role that methodological quality itself plays.     

The competition-among-relations-in-nominals theory of conceptual combination: implications for stimulus class formation and class expansion

One way in which new concepts are added to the conceptual system is through conceptual combination. The competition-among-relations-in-nominals (CARIN) theory (Gagné & Shoben, 1997) proposes that conceptual combination involves specifying a thematic relation (e.g., noun MADE OF modifier) to link the constituent concepts (e.g., chocolate and bee). This theory claims that relations have different strengths for various concepts that correspond to how often a modifier and relation have been paired in previous encounters with combined concepts and that this relational knowledge strongly affects the ease with which combined concepts can be formed. A mathematical model that incorporates key claims of the theory is presented, and empirical findings that are relevant to evaluating the CARIN theory are reviewed. The parallels between the CARIN theory and approaches to stimulus class formation are also discussed.     

Shifts in postdiscrimination gradients within a stimulus dimension based on bilateral facial symmetry

A shift in generalization gradients away from S+ and towards stimuli on the opposite end of the stimulus dimension from S- is a well established phenomenon in the laboratory, occurring with humans and nonhumans and with a wide range of stimuli. The phenomenon of gradient shifts has also been observed to have an analogous relationship to a variety of apparent biases in preference observed in the natural environment. One way to examine the validity of such analogies is by examining whether gradient shifts can be observed with complex and naturalistic stimuli. In the present experiment, undergraduates were trained to discriminate between faces that varied in terms of relative bilateral facial symmetry (a stimulus dimension correlated with health and attractiveness). Comparisons were made within subjects, using two sets of images. For both sets, the faces varied from naturally asymmetrical to symmetrical, and S+ was a face equidistant to the two extremes. With one set, S- was the naturally asymmetrical face, and with the other, S- was the symmetrical face. A peak shift was obtained in both conditions, although the effect was clearer in the aggregate than on the level of the individual. Overall, the results are consistent with the view that the processes responsible for gradient shifts in the lab are relevant to judgments made in the natural environment.     

A Test of Order-Constrained Hypotheses for Circular Data With Applications to Human Movement Science

Researchers studying the movements of the human body often encounter data measured in angles (e.g., angular displacements of joints). The evaluation of these circular data requires special statistical methods. The authors introduce a new test for the analysis of order-constrained hypotheses for circular data. Through this test, researchers can evaluate their expectations regarding the outcome of an experiment directly by representing their ideas in the form of a hypothesis containing inequality constraints. The resulting data analysis is generally more powerful than one using standard null hypothesis testing. Two examples of circular data from human movement science are presented to illustrate the use of the test. Results from a simulation study show that the test performs well.     

Strategy instruction for writing composition at school and at home

Abstract

The objectives of this study are 1) to analyze the effectiveness of a writing composition intervention program aimed to increase children's writing performance and other personal variables; 2) to analyze whether implementation in the environment (school and home) or responsible figures (parents and teachers) produced different effects in program effectiveness; and 3) to check whether increasing parental involvement in doing homework was sufficient to improve children's outcomes or whether prior family training is required to enable them to be efficient. The sample consisted of 112 students (5th-6th grade) and their families. 26 of them made up the EFP group (mothers implementing a writing program), 25 of them were assigned to the PAD group (mothers increasing help with writing homework), 35 to the PRO group (teachers applying a writing program) and 26 to the OC group (ordinary curriculum). We analyze the results and present and discuss our conclusions.     

The role of temporal context and expectancy in resource allocation to and perception of rapid serial events

The perception of target events presented in a rapid stream of non-targets is impaired for early target positions, but then gradually improves, a phenomenon known as attentional awakening. This phenomenon has been associated with better resource allocation. It is unclear though whether improved resource allocation and attentional awakening are a consequence of the temporal context, that is, the position of the target event in the stimulus stream, or are due to a simple expectancy or foreperiod effect. Expectancy is an alternative explanation of attentional awakening because it depends on the a posteriori probabilities, which will increase with target position when all target positions are equally likely. To differentiate between the expectancy and the temporal context account the a priori (objective) probability of target position was defined such that the a posteriori probability would be high for early and late, and low for intermediate target positions. EEG was collected and the P3 ERP evoked by target events was derived as an indicator of resource allocation. A robust attentional awakening effect was observed. The relationships between measures of performance and P3 amplitude, and respectively target position, a priori, and a posteriori probability were analyzed. Results showed that in contrast to target position, a posteriori probability had little impact on performance and did not moderate the association between P3 amplitude and performance. Results also indicated that in spite of the evident role of target position on resource allocation and the perception of target events in rapid stimulus streams, target position is likely not the only variable these are affected by. Nevertheless, the findings of the present study suggest that whereas the temporal context of a rapid serial event is a key player for resource allocation to and perception of the event, expectancy seems of very little consequence.