Fitting correlated residual error structures in nonlinear mixed-effects models using SAS PROC NLMIXED

Nonlinear mixed-effects (NLME) models remain popular among practitioners for analyzing continuous repeated measures data taken on each of a number of individuals when interest centers on characterizing individual-specific change. Within this framework, variation and correlation among the repeated measurements may be partitioned into interindividual variation and intraindividual variation components. The covariance structure of the residuals are, in many applications, consigned to be independent with homogeneous variances, $ {\sigma}^2{\mathbf{I}}_{n_i} $ , not because it is believed that intraindividual variation adheres to this structure, but because many software programs that estimate parameters of such models are not well-equipped to handle other, possibly more realistic, patterns. In this article, we describe how the programmatic environment within SAS may be utilized to model residual structures for serial correlation and variance heterogeneity. An empirical example is used to illustrate the capabilities of the module.     

Use of internal consistency coefficients for estimating reliability of experimental task scores

Reliabilities of scores for experimental tasks are likely to differ from one study to another to the extent that the task stimuli change, the number of trials varies, the type of individuals taking the task changes, the administration conditions are altered, or the focal task variable differs. Given that reliabilities vary as a function of the design of these tasks and the characteristics of the individuals taking them, making inferences about the reliability of scores in an ongoing study based on reliability estimates from prior studies is precarious. Thus, it would be advantageous to estimate reliability based on data from the ongoing study. We argue that internal consistency estimates of reliability are underutilized for experimental task data and in many applications could provide this information using a single administration of a task. We discuss different methods for computing internal consistency estimates with a generalized coefficient alpha and the conditions under which these estimates are accurate. We illustrate use of these coefficients using data for three different tasks.     

Religion and Spirituality among American Indian,South Asian,Black, Hispanic/Latina,and White Women in the Study on Stress,Spirituality, and Health

Social scientists have increasingly recognized the lack of diversity in survey research on American religion, resulting in a dearth of data on religion and spirituality (R/S) in understudied racial and ethnic groups. At the same time, epidemiological studies have increasingly diversified their racial and ethnic representation, but have collected few R/S measures to date. With a particular focus on American Indian and South Asian women (in addition to Blacks, Hispanic/Latinas, and white women), this study introduces a new effort among religion and epidemiology researchers, the Study on Stress, Spirituality, and Health. This multicohort study provides some of the first estimates of R/S beliefs and practices among American Indians and U.S. South Asians, and offers new insight into salient beliefs and practices of diverse racial/ethnic and religious communities.     

Consistency of handedness, regardless of direction, predicts baseline memory accuracy and potential for memory enhancement

Research has shown that consistently right-handed individuals have poorer memory than do inconsistently right- or left-handed individuals under baseline conditions but more reliably exhibit enhanced memory retrieval after making a series of saccadic eye movements. From this it could be that consistent versus inconsistent handedness, regardless of left/right direction, is an important individual difference factor in memory. Or, more specifically, it could be the presence or absence of consistent right-handedness that matters for memory. To resolve this ambiguity, we compared consistent and inconsistent left- and right-handers on associative recognition tests taken after saccades or a no-saccades control activity. Consistent-handers exhibited poorer memory than did inconsistent-handers following the control activity, and saccades enhanced retrieval for consistent-handers only. Saccades impaired retrieval for inconsistent-handers. None of these effects depended on left/right direction. Hence, this study establishes handedness consistency, regardless of direction, as an important individual difference factor in memory.     

Self-efficacy and social support as predictors of smoking after a quit attempt

Abstract

The current study examined self-efficacy and social support as predictors of maintenance after an attempt to stop smoking. As in previous studies, self-efficacy at the end of treatment was a significant predictor of reported smoking during the follow-up period. At 3 months after treatment the prediction from self-efficacy was weaker than a prediction from the level of post-treatment smoking. However at 10 months self-efficacy was the strongest predictive variable assessed in the study. In contrast, social support for the quit attempt was not a significant predictor of maintenance at any stage. The results provided qualified support for the contention that self-efficacy can often be a more powerful predictor than previous performance attainments, especially under conditions of greater situational change.     

Creep behaviour of ice single crystals loaded in torsion explained by dislocation cross-slip

Torsion creep experiments are carried out in order to understand the physics of ice plasticity. A dislocation spreading mechanism based on double cross-slip of basal dislocations is proposed to explain the strong plastic anisotropy and the power law relationship between stress and strain rates. The scenario is tested using three-dimensional dislocation dynamics simulations. Numerical investigations give a stress exponent n?=?2.3 in agreement with experimental measurements. This dislocation spreading mechanism sheds a new light on the interpretation of former experimental observations.     

The Effects of Two Different Reading Acceleration Training Programs on Improving Reading Skills of Second Graders

It has been well established that poor reading skills in the first grades of primary school can lead to poor reading skills in all coming years. A reading acceleration program (RAP) known to improve reading skills in adults and children with and without reading difficulties (RD) was tested for its effect on children in second grade with standard reading skills. The influence of the RAP on improving all reading skills—decoding, fluency, and reading comprehension—was examined. Seventy-nine children in second grade were divided into two study groups and one control group. Each study group received a training program that emphasizes reading skills: decoding, fluency, and comprehension were trained at the levels of words and sentences in Version A and at the levels of words and paragraphs in Version B. Both programs significantly improved reading skills compared with the control group that was not trained: Group A improved word fluency whereas Group B improved accuracy measures (word, pseudo-word, and text). Both training groups showed significantly greater improvement over time than the control group on reading comprehension. We conclude that a RAP training that combines words, sentences, and paragraphs is the most effective for improving reading skills.     

A Population Study of Victimization, Relationships, and Well-Being in Middle Childhood

The paper presents a population-based study on the association of victimization and peer and adult relationships with children’s life satisfaction, self-esteem, anxiety, and depressive symptoms. The study extends previous research by examining 2-, 3-, and 4-way higher-order interaction effects (moderation hypotheses) of adults and peer relationships, victimization, and gender on positive and negative aspects of children’s well-being. The study draws from a representative population-level sample of 2,792 4th graders (M _age = 9.70 years; 48.2 % girls). Data were obtained via student self-report survey on the Middle Years Development Instrument (MDI). Given the nested data (children within classrooms), we employed multi-level regression analyses. Positive relationships with adults and peers were most strongly associated with life satisfaction and self-esteem, whereas victimization was most strongly associated with depressive symptoms and anxiety. No significant 2- or 3-way interactions were identified. The 4-way interaction of gender, adult connectedness, peer connectedness, and victimization was significant for three outcomes; that is, victimization was particularly strongly associated with low life satisfaction, low self-esteem, and high depressive symptoms for girls with low self-reports of peer and adult connectedness. The findings have implications for promoting children’s well-being in school and community contexts, corroborating interventions that foster relationship-building skills and simultaneously reduce victimization.     

Enhancing Athletic Performance Using Digital Video in Consulting

Video has been used successfully in psychosocial interventions to help train communication skills, document behaviors, and as a feedback tool for behavior modification strategies. The need for equipment portability, together with editing expertise, has limited video use in sport psychology. Newer digital video systems help overcome these problems, meaning that sport psychologists can readily use this technology in the field. We discuss and provide experiential observations of how digital video can be used to improve player, coach, and team performance. Also reviewed are new consultation opportunities for sport psychologists with video skills. These new areas center on perceptual skills training and talent identification using perceptual skills testing.     

Family Involvement in a Whole-School Bullying Intervention: Mothers’ and Fathers’ Communication and Influence with Children

Research indicates that involving families in school efforts to prevent and manage bullying behaviour is essential to success. Parents can influence their children's involvement in bullying situations by modelling positive social behaviour, offering advice about appropriate responses to bullying, and encouraging help-seeking. This paper reports family-related findings from the three-year group randomized control trial of the Friendly Schools Friendly Families (FSFF) intervention, which provided training and whole-school, classroom and family resources to build the capacity of schools to prevent bullying victimization and perpetration. Over 1400 parents and carers of Grades 2, 4 and 6 school students completed a survey at baseline and two post-tests. Parents exposed to the FSFF parent component received resources about ways to reduce bullying, build parenting skills and enhance parent–child communication; they also completed home activities with their children; and were encouraged to engage with their children’s school to reduce bullying. Mothers and fathers reported significant increases in the frequency of discussions with their child about bullying. Mothers were more likely than fathers to give pro-social, passive and help-seeking advice compared to fathers, who were more likely to encourage their child to ‘fight back’. The intervention improved fathers’ perceptions of their influence on children’s responses to being bullied. These results highlight the importance of working with both male and female caregivers when addressing children’s bullying behaviour. The findings also demonstrate that a parent intervention can have a positive impact on parent–child communication about bullying when it is an integral part of a whole-school approach.