The baton exchange during the 4×100 m relay: a mathematical analysis

Using mathematical analysis, we examined the three baton exchanges that occur during a 4×100 m relay. Identical representative 100 m running performances were assumed for each of four elite male athletes, and the calculations were made for optimal or near-optimal positions of the baton exchanges and starting positions of the athletes running the second, third and fourth legs as determined by Ward-Smith and Radford (2002). In this paper, we focus on the calculation of the checkmark position and demonstrate the complexity of the baton exchange process. The results of the mathematical analysis show that, for optimal performance, the checkmark should be located differently for each of the three exchanges in a single race, and is further affected by lane draw and free distance (the distance between the runners at the baton exchange). For a representative free distance of 1 m at each exchange, the checkmark distance ranges from a minimum of 11.04 m at the third exchange in Lane 1 to 12.20 m for the first exchange in Lane 8. Failure by teams and their coaches to consider adequately the complexities of the baton exchanges may help explain why 25.5% of teams in recent World Championships were disqualified or did not finish.     

A Unified Theory of Development: A Dialectic Integration of Nature and Nurture

The understanding of nature and nurture within developmental science has evolved with alternating ascendance of one or the other as primary explanations for individual differences in life course trajectories of success or failure. A dialectical perspective emphasizing the interconnectedness of individual and context is suggested to interpret the evolution of developmental science in similar terms to those necessary to explain the development of individual children. A unified theory of development is proposed to integrate personal change, context, regulation, and representational models of development.     

Parents' roles in shaping early adolescents' occupational aspirations

Relations among dimensions of parenting and adolescents' occupational aspirations were examined in two specific domains: academics and sports. The sample consisted of 444 seventh graders, with approximately equal numbers of African American and European American males and females, from two-parent nondivorced families. Multiple measures were used as indicators of parents' values and behaviors, youths' values and beliefs, positive identification with parents, and adolescents' occupational aspirations. In the academic domain, parents' values predicted youths' values directly rather than indirectly through their behaviors. In contrast, fathers' behaviors mediated the relation between parents' and youths' values in the sports domain. Positive identification was directly related to adolescents' values (especially about academics); however, positive identification did not moderate the transmission of values from parent to child in either domain. Parents' values predicted adolescents' occupational aspirations via both direct and indirect pathways. Similar results were obtained for African American and European American males and females. These findings highlight the potential role of parents as socializers of achievement-related values, and, ultimately, adolescents' occupational visions of themselves in the future.     

Learning of Core Disciplinary Ideas: Efficacy Comparison of Two Contrasting Modes of Science Instruction

Science curricula and teaching methods vary greatly, depending in part on which facets of science are emphasized, e.g., core disciplinary ideas or science practices and process skills, and perspectives differ considerably on desirable pedagogies. Given the multi-faceted nature of science and the variety of teaching methods found in practice, it is no simple task to determine what teaching approaches might be most effective and for what purposes. Research into relative efficacy faces considerable challenges, with confounding factors, ambiguities, conflations, and lack of controls being threats to validity. We provide a conceptual framework characterizing the many teaching strategies found in practice as being variants of two fundamental contrasting epistemic modes, and we disentangle conflations of terms and confusions of constructs in both teaching practice and research. Instructional units for two science topics were developed in parallel in the alternative epistemic modes, differing in concept learning paths but otherwise equivalent. We conducted a randomized controlled study of the comparative efficacy of the two modes for learning core disciplinary ideas, using operationally defined active-direct and guided-inquiry teaching methods. Five middle school teachers taught each unit in both modes over 4 years of classroom trials in an 8-day summer program for eighth grade students. Student understanding of core ideas was assessed using pre- and post-tests, and learning gains were analyzed by mode, teacher, topic, and trial year. Although routes to concept understanding were very different in the two modes, eventual student learning gains were similar, within statistical variation. Efficacy variations between and within teachers were greater than between modes, indicating the importance of teacher effects on student achievement. Findings suggest that teachers need not be bound to one mode throughout and can flexibly decide on the pedagogical approach for each concept and situation, on several grounds other than efficacy of core content acquisition alone.     

Familial risk and child competence

Components of familial risk are examined in the context of a 4-year longitudinal study of children with mentally ill mothers. The risk factors examined are parental mental health, social status, parental perspectives, and family stress. The interactions among the risk factors were found to be complex in nature and different for child cognitive and social-emotional competence. These findings are discussed in the context of a systems approach to development in general, and to the development of children at risk in particular. Parental beliefs, attitudes, and coping abilities are hypothesized to be important mediators between environmental stress and child competencies.     

Infant Temperament Measured by Multiple Observations and Mother Report

Observers and mothers rated infant behavior ( n = 50) in the home on dimensions of temperament once a week for 8 weeks. Although week-to-week correlations were modest (intraclass correlations of .14–.36), aggregates of the 8 observations had high reliability for both observers and mothers. Mother reports were tied to our observation sessions by having mothers ( a ) rate their infants' behavior during the period when our observations were made and ( b ) use a questionnaire that mirrored the scoring system used for scoring the videotaped observation sessions. When direct observations were compared with mother reports (on the aggregated weekly reports and on 4 widely used questionnaires), little evidence of mother-observer correspondence was found. The interpretation of the large literature that has used maternal report is discussed, as well as the importance of direct observation of infant behavior when temperament is assessed.     

Determinants of Complexity in Mexican-American and Anglo-American Mothers' Conceptions of Child Development

Complexity of parental reasoning about child development was studied in mothers who varied in ethnic background and biculturalism. Middle-class mothers from Mexican-American and Anglo-American backgrounds were compared on their level of concepts of development on a scale from categorical to perspectivistic reasoning. Categorical mothers interpreted child development as being caused by single constitutional or environmental factors. Perspectivistic mothers interpreted development as the result of the dynamic interplay between constitution and environment over time and accepted that the same developmental outcome could have multiple determinants. In a comparison among moderately acculturated Mexican-Americans, highly acculturated Mexican Americans, and Anglo Americans, the highly acculturated Mexican-American group scored as more perspectivistic than the other two groups, despite the fact that the Anglo-Americans were the most acculturated. When the 2 Mexican-American groups were subdivided into monocultural (Mexican or American) and bicultural subgroups and compared with the Anglo-American group, the bicultural subgroup of the highly acculturated Mexican-American mothers was the most perspectivistic. These results suggest a complex picture of diversity in Mexican-American mothers who retain values and beliefs from their own culture, as well as taking on values and beliefs of the American culture. Maternal intelligence and adherence to traditional cultural values were not found to correlate significantly with level of developmental reasoning.     

Do We Have a Trust Problem? Exploring Undergraduate Student Views on the Tentativeness and Trustworthiness of Science

Science & Education - Science includes the fundamental attributes of durability and uncertainty; hence, we teach about the “tentative yet durable” nature of science. Public...