Heuristic method for label placement in scatterplots

Kuhfeld (1986) has proposed several alternative scatterplot routines with labeled points. To this list is added a heuristic routine that repositions labels to eliminate overlap while attempting to maximize the number of labels presented in a metric plot.I would like to thank the reviewer of a previous version of this paper for several excellent suggestions for future modifications of both the label positioning routine and the overall plotting package.     

The social-cognitive model of achievement motivation and the 2 x 2 achievement goal framework

Two studies examined hypotheses drawn from a proposed modification of the social-cognitive model of achievement motivation that centered on the 2 x 2 achievement goal framework. Implicit theories of ability were shown to be direct predictors of performance attainment and intrinsic motivation, and the goals of the 2 x 2 framework were shown to account for these direct relations. Perceived competence was shown to be a direct predictor of achievement goals, not a moderator of relations implicit theory or achievement goal effects. The results highlight the utility of attending to the approach-avoidance distinction in conceptual models of achievement motivation and are fully in line with the hierarchical model of achievement motivation.     

The effects of interval duration on temporal tracking and alternation learning

On cyclic-interval reinforcement schedules, animals typically show a postreinforcement pause that is a function of the immediately preceding time interval (temporal tracking). Animals, however, do not track single-alternation schedules-when two different intervals are presented in strict alternation on successive trials. In this experiment, pigeons were first trained with a cyclic schedule consisting of alternating blocks of 12 short intervals (5 s or 30 s) and 12 long intervals (180 s), followed by three different single-alternation interval schedules: (a) 30 s and 180 s, (b) 5 s and 180 s, and (c) 5 s and 30 s. Pigeons tracked both schedules with alternating blocks of 12 intervals. With the single-alternation schedules, when the short interval duration was 5 s, regardless of the duration of the longer interval, pigeons learned the alternation pattern, and their pause anticipated the upcoming interval. When the shorter interval was 30 s, even when the ratio of short to long intervals was kept at 6:1, pigeons did not initially show anticipatory pausing-a violation of the principle of timescale invariance.     

Genetically influenced change in sensation seeking drives the rise of delinquent behavior during adolescence

Sensation seeking is associated with an increased propensity for delinquency, and emerging research on personality change suggests that mean levels of sensation seeking increase substantially from childhood to adolescence. The current study tested whether individual differences in the rate of change of sensation seeking predicted within-person change in delinquent behavior and whether genetically influenced differences in rate of personality change accounted for this association. Sensation seeking and delinquent behavior were assessed biennially between ages 10-11 and 16-17 in a nationally representative sample of 7675 youths from the National Longitudinal Study of Youth: Children and Young Adults (CNLSY). Analyses using latent growth curve modeling found that within-person change in sensation seeking was significantly and positively correlated with within-person change in delinquency from childhood to adolescence. Furthermore, behavioral genetic analyses of a subset of 2562 sibling pairs indicated that there were substantial genetic influences on both initial levels of sensation seeking and change in sensation seeking during early adolescence, with over 80% of individual differences in change due to genetic factors. Finally, these genetically driven increases in sensation seeking were most important for predicting increases in delinquency, whereas environmental paths between sensation seeking and delinquency were not significant. These results suggest that developmental changes in delinquent behaviors during adolescence are driven by a genetically governed process of personality change.     

Barriers and facilitators to public bicycle scheme use: A qualitative approach

The purpose of this study was to explore barriers and facilitators to using CityCycle, a public bicycle share scheme in Brisbane, Australia. Focus groups were conducted with participants belonging to one of three categories. Group one consisted of infrequent and non-cyclists (no bicycle riding over the past month), group two were regular bicycle riders (ridden a bicycle at least once in the past month) and group three was composed of CityCycle members. A thematic analytic method was used to analyse the data. Three main themes were found: Accessibility/spontaneity, safety and weather/topography. The lengthy sign-up process was thought to stifle the spontaneity typically thought to attract people to public bike share. Mandatory helmet legislation was thought to reduce spontaneous use. Safety was a major concern for all groups and this included a perceived lack of suitable bicycle infrastructure, as well as regular riders describing a negative attitude of some car drivers. Interestingly, CityCycle riders unanimously perceived car driver attitudes to improve when on CityCycle bicycles relative to riding on personal bicycles. Conclusions: In order to increase the popularity of the CityCycle scheme, the results of this study suggest that a more accessible, spontaneous sign-up process is required, 24/7 opening hours, and greater incentives to sign up new members and casual users, as seeing people using CityCycle appears critical to further take up.     

Preschools reduce early academic-achievement gaps: a longitudinal twin approach

Preschools may reduce inequalities in early academic achievement by providing children from disadvantaged families with higher-quality learning environments than they would otherwise receive. In this study, longitudinal data from a nationally representative sample of more than 600 twin pairs were used to estimate the contributions of genes, the shared environment, and the nonshared environment to cognition and achievement scores in children enrolled versus not enrolled in preschool. Attending preschool at age 4 was associated with reductions in shared environmental influences on reading and math skills at age 5, but was not associated with the magnitude of shared environmental influences on cognition at age 2. These prospective effects were mediated by reductions in achievement gaps associated with minority status, socioeconomic status, and ratings of parental stimulation of cognitive development. Lower socioeconomic status was associated with lower rates of preschool enrollment, which suggests that the very children who would benefit most from preschools are the least likely to be enrolled in them.     

Remembering the best and worst of times: Memories for extreme outcomes bias risky decisions

When making decisions on the basis of past experiences, people must rely on their memories. Human memory has many well-known biases, including the tendency to better remember highly salient events. We propose an extreme-outcome rule, whereby this memory bias leads people to overweight the largest gains and largest losses, leading to more risk seeking for relative gains than for relative losses. To test this rule, in two experiments, people repeatedly chose between fixed and risky options, where the risky option led equiprobably to more or less than did the fixed option. As was predicted, people were more risk seeking for relative gains than for relative losses. In subsequent memory tests, people tended to recall the extreme outcome first and also judged the extreme outcome as having occurred more frequently. Across individuals, risk preferences in the risky-choice task correlated with these memory biases. This extreme-outcome rule presents a novel mechanism through which memory influences decision making.