Contraction intensity and velocity on vastus lateralis SEMG power spectrum and amplitude

Effect of contraction intensity [100%, 75%, 50%, and 25% maximum voluntary contraction (MVC)] and movement velocity [0 degrees (isometric)], 50 degrees, 100 degrees, 200 degrees, and 400 degrees/sec. [isovelocities]) on root mean square amplitude (SEMG-RMS) and median frequency power spectrum (SEMG-MNF) of vastus lateralis (VL) surface electromyography was investigated with ten healthy female university students. Peak torque (PT), mean torque (MT), SEMG-MNF, and SEMG-RMS, analyzed using separate repeated-measures analyses of variance (p < or = .05), indicated: (1) an inverse relation between PT and MT and movement velocity, (2) greater SEMG-MNF values during all isovelocity conditions compared with isometric conditions, with highest values occurring at 50 degrees /sec. and at 100% and 75% MVC, and (3) at all contraction intensities SEMG-RMS values were higher during dynamic movements than isometric movements and highest at 200 degrees /sec. Isovelocity contractions were inferred to facilitate a greater recruitment of fast-twitch fibers (via increased SEMG-MNF), which was intensified at 50 degrees /sec., whereas greater overall muscle activation was found at 200 degrees /sec.     

The Heterogeneous P-Median Problem for Categorization Based Clustering

The p-median offers an alternative to centroid-based clustering algorithms for identifying unobserved categories. However, existing p-median formulations typically require data aggregation into a single proximity matrix, resulting in masked respondent heterogeneity. A proposed three-way formulation of the p-median problem explicitly considers heterogeneity by identifying groups of individual respondents that perceive similar category structures. Three proposed heuristics for the heterogeneous p-median (HPM) are developed and then illustrated in a consumer psychology context using a sample of undergraduate students who performed a sorting task of major U.S. retailers, as well as a through Monte Carlo analysis.     

It has been said that, “There are three degrees of falsehoods: Lies,damn lies,and statistics”

Applied behavior analysis (ABA) researchers have historically eschewed population-based, inferential statistics, preferring to conduct and analyze repeated observations of each participant's responding under carefully controlled and manipulated experimental conditions using single-case designs (SCDs). In addition, early attempts to adapt traditional statistical procedures for use with SCDs often involved trade-offs between experimental and statistical control that most ABA researchers have found undesirable. The statistical methods recommended for use with SCDs in the current special issue represent a welcome departure from such prior suggestions in that the current authors are proposing that SCD researchers add statistical methods to their current practices in ways that do not alter traditional SCD practices. Further refinement and use of such methods would (a) facilitate the inclusion of research using SCDs in meta-analyses and (b) aid in the development and planning of grant-funded research using SCD methods. Collaboration between SCD researchers and statisticians, particularly on research that demonstrates the benefit of these methods, may help promote their acceptance and use in ABA.     

Looking back and falling further behind: The moderating role of rumination on the relationship between organizational politics and employee attitudes,well-being,and performance

The current study tested the theoretically relevant, yet previously unexamined, role of rumination on the relationship between politics perceptions and a variety of threat responses. Drawing from Response Styles Theory, it was argued that rumination amplifies the effects of politics by enhancing the influence of negative information on cognition, interfering with problem-solving, and undermining sources of social support. The work stress literature, along with extant politics research, served to identify four variables – job satisfaction, tension, depressed work mood, and employee effort/performance – that served as study outcomes. Across three unique samples, hypothesized relationships were strongly supported, indicating that politics perceptions negatively affected work outcomes of high ruminators, but demonstrate little influence on those who engage in less rumination. Moreover, the nonlinear influences of the focal constructs were considered and the results confirmed atypical relational forms. Contributions, implications for theory and practice, strengths and limitations, and future research directions are described.     

Teacher and Parent Perceptions of Relational and Physical Aggression During Early Childhood

Although links have been found between parents’ and teachers’ (caregivers’) attitudes about aggressive behavior, their responses to aggressive behaviour in children, and those children’s own use of aggressive behaviour, most research has focused on primary and secondary school contexts and has examined the influence of parents and teachers separately. The current study explored both parents’ and teachers’ beliefs and intervention strategies for relational and physical aggression in early childhood settings. Teachers (N?=?18; Mage?=?34.8 years) and parents (N?=?68; Mage?=?32.2 years) were presented with vignettes portraying relational and physical aggression. Following each vignette, their perceptions of the seriousness of the act, empathy for the victim, likelihood to intervene, and intervention strategies used to respond to each vignette were assessed. Teachers were also interviewed about examples of aggression that have been seen in preschool age children. Results indicated that caregivers viewed relational compared to physical aggression as more normative, and had less empathy for, and were less likely to intervene in instances of relationally aggressive behaviour. They also recommended more passive intervention strategies towards relationally aggressive children and more direct strategies towards physically aggressive children. Interview responses indicated that teachers perceived the primary cause of aggression to be related to developmental characteristics of the child. Implications for how these findings about adult–child interactions impact the development of relational and physical aggression are discussed.