Common functional principal components analysis: a new approach to analyzing human movement data

In many human movement studies angle-time series data on several groups of individuals are measured. Current methods to compare groups include comparisons of the mean value in each group or use multivariate techniques such as principal components analysis and perform tests on the principal component scores. Such methods have been useful, though discard a large amount of information. Functional data analysis (FDA) is an emerging statistical analysis technique in human movement research which treats the angle-time series data as a function rather than a series of discrete measurements. This approach retains all of the information in the data. Functional principal components analysis (FPCA) is an extension of multivariate principal components analysis which examines the variability of a sample of curves and has been used to examine differences in movement patterns of several groups of individuals. Currently the functional principal components (FPCs) for each group are either determined separately (yielding components that are group-specific), or by combining the data for all groups and determining the FPCs of the combined data (yielding components that summarize the entire data set). The group-specific FPCs contain both within and between group variation and issues arise when comparing FPCs across groups when the order of the FPCs alter in each group. The FPCs of the combined data may not adequately describe all groups of individuals and comparisons between groups typically use t-tests of the mean FPC scores in each group. When these differences are statistically non-significant it can be difficult to determine how a particular intervention is affecting movement patterns or how injured subjects differ from controls. In this paper we aim to perform FPCA in a manner allowing sensible comparisons between groups of curves. A statistical technique called common functional principal components analysis (CFPCA) is implemented. CFPCA identifies the common sources of variation evident across groups but allows the order of each component to change for a particular group. This allows for the direct comparison of components across groups. We use our method to analyze a biomechanical data set examining the mechanisms of chronic Achilles tendon injury and the functional effects of orthoses.     

Generalized others and imaginary audiences: A neo-Meadian approach to adolescent egocentrism

Piaget’s conception of adolescent egocentrism, as interpreted and extended by Elkind (1967) is discussed, and research that has related Elkind’s egocentric ideations of personal fable and imaginary audience to age and intellectual development is considered. Alternative theories of adolescent egocentrism and its decentration are examined, and a neo-Meadian framework is discussed that understands the imaginary audience ideation of adolescents as a possibly functional, highly variable response to the complex task of coordinating individual and social perspectives as part of the adolescent’s search for identity.     

Associations between types of combat violence and the acquired capability for suicide

Research suggests that combat exposure might increase risk for suicide. The interpersonal-psychological theory of suicide (IPTS) proposes that exposure to painful and provocative experiences such as combat contribute to fearlessness about death and increased pain tolerance, which serve to enhance the individual's capability to attempt suicide. Violent and aggressive combat experiences, in particular, should demonstrate relatively stronger associations to this capability. The current study tests this proposition in a sample of deployed active duty combatants. Results indicate that all types of combat exposure independently contribute to capability for suicide. Consistent with the IPTS, when considering all types of combat simultaneously, combat characterized by violence and high levels of injury and death are associated with relatively stronger associations to this capability.     

The Predictive Validity of Injury Proxies: Predicting Early Adolescent Injuries with Assessments of Minor Injuries

This study offers an initial step in establishing the predictive validity of injury proxies. Proxies are utilized frequently by injury researchers to overcome various methodological and ethical issues inherent in injury research, although psychometric data on proxies are limited. Using data from the NICHD Study of Early Child Care and Youth Development we found that minor injuries predicted adolescent injuries longitudinally, even in the context of well-established predictors of injury risk. This study is the first to demonstrate the predictive validity of minor injuries, a common proxy of pediatric injury risk. Findings are discussed with respect to implications for conceptual understanding of injury risk, future research, and prevention efforts.     

Measuring Relationships between Personality,Knowledge, and Performance using Single‐response Situational Judgment Tests

We report two studies that investigate single‐response situational judgment tests (SJTs) as measures of job knowledge. Study 1 examines relationships between job knowledge measured by a single‐response SJT, personality, and performance for museum tour guides. Study 2 extends Study 1's findings with a sample of volunteers using a single‐response SJT about volunteerism. In both studies, personality was related to knowledge, and knowledge predicted performance. In Study 2, knowledge accounted for incremental variance in performance beyond personality, but personality added no incremental variance beyond knowledge. Results suggest that knowledge of effective behavior and knowledge of ineffective behavior are separate constructs. These studies demonstrate the validity of single‐response SJTs and provide evidence that knowing what to do and what not to do are separate domains.     

Preliminary Evidence for Associations of CHRM2 with Substance Use and Disinhibition in Adolescence

Evidence for shared heritable influences across domains of substance use suggests that some genetic variants influence broad risk for externalizing behaviors. Theories of externalizing psychopathology also suggest that genetic liability for substance use manifests as temperamental risk factors, particularly those related to behavioral disinhibition, during adolescence. The cholinergic muscarinic receptor 2 gene (CHRM2) is a promising candidate for studying genetic influences on broad-based risk for externalizing traits. This study examined a candidate CHRM2 polymorphism (rs1455858) in relation to substance use and personality measures of disinhibition in a sample of high-risk adolescents (n?=?124). Bivariate analyses and structural equation modeling (SEM) evaluated associations of rs1455858 with measures of drug involvement (alcohol, tobacco and marijuana) and disinhibition (indexed by impulsivity and sensation seeking scores). Bivariate analyses showed significant associations of CHRM2 with several behavioral phenotypes. In SEM analyses CHRM2 related significantly to latent measures of substance use and disinhibition; additionally, disinhibition mediated the association of CHRM2 with substance use. These results suggest that CHRM2 variants are potentially relevant for adolescent substance use and that temperamental risk factors could contribute to these associations.     

Assessing within-person personality variability via frequency estimation: More evidence for a new measurement approach

Variability in personality has been recognized in recent years as an important aspect of personality both conceptually and empirically. A relatively new and efficient method of obtaining variability information is frequency-based personality assessment (Edwards & Woehr, 2007). The purpose of the present research is to further examine the viability of frequency-based personality measurement as an alternative to traditional (Likert-type) measurement and to assess the usefulness of the variance-based parameters. Toward this end, three studies are presented. Specifically, Study 1 examined relationships between a frequency-based measure of the Big Five personality traits and several motivational variables. Study 2 examined the moderating role of temporal consistency information (provided by frequency-based measurement) on relationships between personality and peer ratings of task performance. Study 3 compared the frequency-based measure to a Likert-type measure with respect to each measure’s susceptibility to deliberate response distortion. Results indicated that consistency information increases the predictive validity of agreeableness and conscientiousness and that a frequency-based format is less susceptible to faking than a Likert-type format for conscientiousness, emotional stability, and openness to experience.     

Calling and work-related outcomes: Career commitment as a mediator

The current study tested the hypothesis that experiencing a calling to a particular career would relate positively to work-related outcomes, and that these relations would be mediated by career commitment. Using a sample of 370 employees representing diverse occupations at a Western research university, results supported these hypotheses as calling moderately correlated with career commitment, job satisfaction, and organizational commitment and weakly correlated with withdrawal intentions. Career commitment was found to fully mediate the calling–job satisfaction relation, partially mediate the calling–organizational commitment relation, and act as a suppressor in the relation between calling and withdrawal intentions; calling was associated with somewhat greater withdrawal intentions once a person's level of career commitment was taken into consideration. These results suggest that career commitment may represent a critical link between calling and work-related well-being. Implications for research and practice are explored.     

Interteaching: the impact of lectures on student performance

Several studies suggest that interteaching improves student learning more than traditional lectures, but few have examined which components of interteaching contribute to its efficacy. We examined whether the lecture component of interteaching affected students' exam grades and cumulative point totals in a research methods course. Although students who received lectures had consistently higher exam scores than students who did not, the differences were statistically significant on only 2 of 5 exams. Students who received lectures, however, earned significantly more points during the semester.