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Little Empirical Support (little + empirical_support)
Selected AbstractsThe effects of adolescent cannabis use on educational attainment: a reviewADDICTION, Issue 11 2000Michael Lynskey This paper reviews research examining the link between cannabis use and educational attainment among youth. Cross-sectional studies have revealed significant associations between cannabis use and a range of measures of educational performance including lower grade point average, less satisfaction with school, negative attitudes to school, increased rates of school absenteeism and poor school performance. However, results of cross-sectional studies cannot be used to determine whether cannabis use causes poor educational performance, poor educational performance is a cause of cannabis use or whether both outcomes are a reflection of common risk factors. Nonetheless, a number of prospective longitudinal studies have indicated that early cannabis use may significantly increase risks of subsequent poor school performance and, in particular, early school leaving. This association has remained after control for a wide range of prospectively assessed covariates. Possible mechanisms underlying an association between early cannabis use and educational attainment include the possibility that cannabis use induces an 'amotivational syndrome' or that cannabis use causes cognitive impairment. However, there appears to be relatively little empirical support for these hypotheses. It is proposed that the link between early cannabis use and educational attainment arises because of the social context within which cannabis is used. In particular, early cannabis use appears to be associated with the adoption of an anti-conventional lifestyle characterized by affiliations with delinquent and substance using peers, and the precocious adoption of adult roles including early school leaving, leaving the parental home and early parenthood. [source] CAN INTRASPECIFIC COMPETITION DRIVE DISRUPTIVE SELECTION?EVOLUTION, Issue 3 2004AN EXPERIMENTAL TEST IN NATURAL POPULATIONS OF STICKLEBACKS Abstract Theory suggests that frequency-dependent resource competition will disproportionately impact the most common phenotypes in a population. The resulting disruptive selection forms the driving force behind evolutionary models of niche diversification, character release, ecological sexual dimorphism, resource polymorphism, and sympatric speciation. However, there is little empirical support for the idea that intraspecific competition generates disruptive selection. This paper presents a test of this theory, using natural populations of the three-spine stickleback, Gasterosteus aculeatus. Sticklebacks exhibit substantial individual specialization associated with phenotypic variation and so are likely to experience frequency-dependent competition and hence disruptive selection. Using body size and relative gonad mass as indirect measures of potential fecundity and hence fitness, I show that an important aspect of trophic morphology, gill raker length, is subject to disruptive selection in one of two natural lake populations. To test whether this apparent disruptive selection could have been caused by competition, I manipulated population densities in pairs of large enclosures in each of five lakes. In each lake I removed fish from one enclosure and added them to the other to create paired low- and high-population-density treatments with natural phenotype distributions. Again using indirect measures of fitness, disruptive selection was consistently stronger in high-density than low-density enclosures. These results support long-standing theoretical arguments that intraspecific competition drives disruptive selection and thus may be an important causal agent in the evolution of ecological variation. [source] Content Validation Is Useful for Many Things, but Validity Isn't One of ThemINDUSTRIAL AND ORGANIZATIONAL PSYCHOLOGY, Issue 4 2009KEVIN R. MURPHY Content-oriented validation strategies establish the validity of selection tests as predictors of performance by comparing the content of the tests with the content of the job. These comparisons turn out to have little if any bearing on the predictive validity of selection tests. There is little empirical support for the hypothesis that the match between job content and test content influences validity, and there are often structural factors in selection (e.g., positive correlations among selection tests) that strongly limit the possible influence of test content on validity. Comparisons between test content and job content have important implications for the acceptability of testing, the defensibility of tests in legal proceedings, and the transparency of test development and validation, but these comparisons have little if any bearing on validity. [source] Posttraumatic play in young children exposed to terrorism: An empirical study,INFANT MENTAL HEALTH JOURNAL, Issue 2 2010Esther Cohen Dr. The phenomenon of "posttraumatic play" (PTP) has received much clinical recognition and little empirical support. The objective of this study was to examine various aspects of PTP in young children exposed to terror events and their relation to posttraumatic stress disorder (PTSD). Individual play sessions, conducted with 29 young Israeli children directly exposed to terrorism (M age = 5.47, SD = 1.34) and 25 matched unexposed children (M age = 5.62, SD = 0.87), were coded using the Children's Play Therapy Instrument,Adaptation for Terror Research (CPTI-ATR; S.E. Chazan & E. Cohen, 2003). Analyses using these ratings showed (a) significant differences between the two groups, (b) significant associations with the caregiver's reports on child's exposure, and (c) significant associations with the caregiver's reports on the child's PTSD symptoms. Play activity ratings of predominant negative affects, frequent acting-out/morbid themes, lowered developmental level, and reduced awareness of the child of him- or herself as a player significantly predicted more PTSD symptoms. PTP which included more coping strategies classified as "overwhelmed reexperiencing" and less "reenactment with soothing" was associated with a higher level of PTSD. Play analysis with the CPTI-ATR may be helpful in identifying PTSD in children and also guide the selection of therapeutic techniques. [source] The psychophysiology of the maternal,fetal relationshipPSYCHOPHYSIOLOGY, Issue 4 2004Janet A. Dipietro Abstract The enigmatic quality of the maternal,fetal relationship has been extolled throughout history with little empirical support. We apply time series analysis to data for 137 maternal,fetal pairs collected at 20, 24, 28, 32, 36, and 38 weeks gestation. Maternal heart rate and skin conductance data were digitized in tandem with fetal heart rate and motor activity. No temporal relations between fetal heart rate and either maternal variable were found, although averaged maternal and fetal heart rates were correlated from 32 weeks. Consistent temporal associations between fetal movement and maternal heart rate and skin conductance were detected. Fetal movement stimulated rises in each parameter, peaking at 2 and 3 s, respectively. Associations did not change over gestation, were unaffected by a maternal stressor, and showed within-pair stability. The bidirectional nature of the maternal,fetal relationship is considered. [source] Research review: Goals, intentions and mental states: challenges for theories of autismTHE JOURNAL OF CHILD PSYCHOLOGY AND PSYCHIATRY AND ALLIED DISCIPLINES, Issue 8 2009Antonia F. de C. Hamilton The ability to understand the goals and intentions behind other people's actions is central to many social interactions. Given the profound social difficulties seen in autism, we might expect goal understanding to be impaired in these individuals. Two influential theories, the ,broken mirror' theory and the mentalising theory, can both predict this result. However, a review of the current data provides little empirical support for goal understanding difficulties; several studies demonstrate normal performance by autistic children on tasks requiring the understanding of goals or intentions. I suggest that this conclusion forces us to reject the basic broken mirror theory and to re-evaluate the breadth of the mentalising theory. More subtle theories which distinguish between different types of mirroring and different types of mentalising may be able to account for the present data, and further research is required to test and refine these theories. [source] | ||||||||||