Resampling and Distribution of the Product Methods for Testing Indirect Effects in Complex Models

Recent advances in testing mediation have found that certain resampling methods and tests based on the mathematical distribution of 2 normal random variables substantially outperform the traditional z test. However, these studies have primarily focused only on models with a single mediator and 2 component paths. To address this limitation, a simulation was conducted to evaluate these alternative methods in a more complex path model with multiple mediators and indirect paths with 2 and 3 paths. Methods for testing contrasts of 2 effects were evaluated also. The simulation included 1 exogenous independent variable, 3 mediators and 2 outcomes and varied sample size, number of paths in the mediated effects, test used to evaluate effects, effect sizes for each path, and the value of the contrast. Confidence intervals were used to evaluate the power and Type I error rate of each method, and were examined for coverage and bias. The bias-corrected bootstrap had the least biased confidence intervals, greatest power to detect nonzero effects and contrasts, and the most accurate overall Type I error. All tests had less power to detect 3-path effects and more inaccurate Type I error compared to 2-path effects. Confidence intervals were biased for mediated effects, as found in previous studies. Results for contrasts did not vary greatly by test, although resampling approaches had somewhat greater power and might be preferable because of ease of use and flexibility.     

Making it happen: Possibilities and pitfalls of Cunningham's educational semiotic

In fundamental agreement with Cunningham's overall thesis, we attempt in this paper to articulate what an educational semiotic might look like on a practical level. For educational psychologists, it should mean an increased awareness of the limited, localized world views offered by current models of cognition and an increased attentiveness to alternate models. For teachers, an educational semiotic offers integration of cognition and affect and instructional strategies that depend upon and facilitate many ways of knowing. For an educational semiotic to be realized, however, there must be much greater attention paid to the roles of motivation and metacognition in semiotic pedagogy.     

Classically conditioned heart rate and respiratory-motor activity in newborn and neonatal pygmy goats

Classical discrimination conditioning of heart rate (HR) and respiratory-motor (RM) activity was examined in 16 newborn (average age = 1 day) and 8 neonatal (average age = 2 weeks) pygmy goats over 4 days of conditioning involving an electric shock US and auditory CSs. On the 4th day, one-half of the animals in each group received a low to moderate dose of ethanol to test the resistance of the CRs to drug effects. Discriminated conditioning of RM activity but not HR occurred in the newborn group, indicating an absence of close coupling between skeletal-motor activity and HR at this early age. While the newborn group failed to show recognizable HR reactions to the CSs during the 4 days of testing, it did show a long-latency brady-cardia UR beginning at 2 days of age that may have been secondary to baroreceptor reflex actions. The neonatal group displayed conditioning of both HR and RM activity. The similar latencies of the two types of CRs during the CS suggested that they may have been related to each other. However, the fact that the RM CR developed a day before the HR CR, combined with the observation that ethanol modified the HR CR but not the RM CR, supports the view that there was considerable independence between the two types of CRs.     

Integrating Free Computer Software in Chemistry and Biochemistry Instruction: An International Collaboration

At the Universidad de Caldas, Manizales, Colombia, we used their new computer facilities to introduce chemistry graduate students to biochemical database mining and quantum chemistry calculations using freeware. These hands-on workshops allowed the students a strong introduction to easily accessible software and how to use this software to begin to explore computer modeling. Each workshop was scheduled for 2 h and each included a tutorial exercise to familiarize the students with the main menus and features of the software. In addition, accompanying lectures and practical laboratory sections were provided. Both courses were taught in Spanish although the written instructions were in English. This was not a problem since these students have a comfort level with reading English. Student feedback following these workshops was highly enthusiastic and positive. This international collaborative will impact both the teaching and research goals for this cohort of graduate students.     

What Preschool Classroom Experiences Are Associated With Whether Children Improve in Visuomotor Integration?

Research Findings: This study examined the contribution of several class-room experience measures (classroom characteristics, teacher characteristics, and teacher–child interactions) to preschoolers’ improvement in visuomotor integration. Children (N = 467) ranged in age from 3 to 5 years old and were enrolled in 115 classrooms in 5 U.S. states. Children’s visuomotor integration was measured twice (on average 5.2 months apart) using the Beery-Buktenica Developmental Test of Visual-Motor Integration (visuomotor integration subtest). Hierarchical linear models controlling for background characteristics and inhibitory control showed that children improved more in visuomotor integration when they were in classrooms with fewer 3-year-olds, when their teacher had at least a bachelor’s degree, and when teachers demonstrated high quality in their interactions. Practice or Policy: Visuomotor integration, and specifically the ability to copy designs with a writing utensil, is a robust indicator of children’s school readiness and longitudinal achievement. U.S. preschoolers gained more on visuomotor integration in classrooms with fewer 3-year-old children that were taught by a college-educated teacher and when such classrooms provided high-quality organizational and instructional interactions. These results expand the outcomes linked to early childhood education experiences and emphasize the need for well-prepared early childhood teachers who interact with children effectively.