Prevention Effects Moderate the Association of 5-HTTLPR and Youth Risk Behavior Initiation: Gene × Environment Hypotheses Tested via a Randomized Prevention Design

A randomized prevention design was used to investigate a moderation effect in the association between a polymorphism in the SCL6A4 ( 5HTT ) gene at 5-HTTLPR and increases in youths' risk behavior initiation. Participation in the Strong African American Families (SAAF) program was hypothesized to attenuate the link between 5-HTTLPR status and risk behavior initiation. Youths ( N  =   641, M age = 11.2 years) were assigned randomly to a SAAF or control condition. Risk behavior initiation across 29 months was linked positively with the 5-HTTLPR genotype and negatively with SAAF participation. Control youths at genetic risk initiated risk behavior at twice the rate of SAAF youths at genetic risk and youths not at genetic risk in either condition.     

Index of mechanical efficiency in competitive and recreational long distance runners

The purpose of this investigation was to compare external work and net energy expenditure during a bout of repetitive stretch-shortening cycles between competitive and recreational long-distance runners. Participants were divided into either competitive or recreational runners based on their maximal oxygen consumption and self-reported 1600 m times. The stretch-shortening cycle involved a repetitive hopping protocol on a force plate while measuring oxygen consumption and lactate accumulation for a total of 10 min. External work and net energy expenditure were calculated for 3 min after steady state was achieved and the ratio between these variables was utilised as an index of mechanical efficiency. Lower extremity stiffness was calculated during this interval as well. Net energy expenditure was significantly lower in competitive runners (152.6 ± 33.3 kJ) in comparison to recreational runners (200.6 ± 41.4 kJ) (P = 0.02) given similar amounts of external work performed in both groups (competitive runners = 65.6 ± 20.1 kJ, recreational runners = 68.8 ± 12.1 kJ) (P = 0.67). Index of mechanical efficiency was significantly different between competitive runners (43.2 ± 9.0%) and recreational runners (34.8 ± 5.3%) (P = 0.03). No significant differences were found in lower extremity stiffness (P = 0.64). Competitive distance runners can perform similar levels of external work with lower net energy expenditure and thus a higher index of mechanical efficiency during repetitive stretch-shortening cycles in comparison to recreational runners with similar values of lower extremity stiffness. This ability could possibly be due differences in muscle–tendon length changes, muscle pre-activation, cross-bridge potentiation and short-latency reflex responses as a result of training which should be considered for future investigation.     

Chinese Children’s Statistical Learning of Orthographic Regularities: Positional Constraints and Character Structure

This study examined how Chinese children acquire the untaught positional constraints of stroke patterns that are embedded in left–right structured and top–bottom structured characters. Using an orthographic regularity pattern elicitation paradigm, 536 Hong Kong Chinese children at different levels of reading (kindergarten, 2nd, and 5th grades) were asked to produce invented characters with left–right and top–bottom stroke pattern pairs. Even kindergartners were aware of the positional constraints of stroke patterns and were able to produce orthographically legal pseudocharacters with different stroke pattern pairs. This ability improved across grade level. Moreover, there was a production asymmetry in which children produced more top–bottom structured pseudocharacters than left–right structured pseudocharacters. The error pattern analysis further revealed that more positional errors were observed in producing left–right structured noncharacters than in the top–bottom structured noncharacters. This production asymmetry seemed to reflect children’s experience with a distribution asymmetry observed between left–right (59.19%) and top–bottom structured characters (23.46%) in a corpus of school Chinese. These results are discussed within the framework of statistical learning of orthographic regularity in Chinese.     

Response Time Differences Between Computers and Tablets

Item response time data were used in investigating the differences in student test-taking behavior between two device conditions: computer and tablet. Analyses were conducted to address the questions of whether or not the device condition had a differential impact on rapid guessing and solution behaviors (with response time effort used as an indicator) as well as on the time that students spent on the test (reading, mathematics, and science) or a given item type (such as drag-and-drop and fill in blank). Further analyses were conducted to examine if the potential impact of device conditions varied by gender and ethnicity groups. Overall there were no significant differences in response time effort related to device, although some differences related to item type and test sequence were noted. Students tended to spend slightly more time when taking the tests and certain types of items on the tablet than on the computer. No interactions of device with gender or ethnicity were observed. Follow-up research on the item time thresholds is discussed.