Simulating the impact during human jumping by means of a 4-degrees-of-freedom model with time-dependent properties

The authors simulated the vertical movements of a jumper and the force time courses by means of a 4-degrees-of-freedom model consisting of 4 masses, springs, and dampers. Of the motions simulated, only that of the mass imitating the trunk corresponded to the measured data. The best fit to the measured force curves were obtained in the simulation in which time-dependent model parameters were used. From the results, the authors concluded that at the beginning of the landing, a jumper behaves like a 2-mass model in which the leg segments (thighs, shanks, and feet) effectively combine into 1 mass. After approximately 60 ms, the connections between the leg segments become more compliant and the jumper behaves like a 4-mass model with a soft coupling between the leg segments. The process is equivalent to an increase of the degrees of freedom of the movements. At the end of the ground contact phase during hopping, the jumper has to contract the muscles in order to reach the envisaged jump height. In the model, that contraction could not be satisfactorily simulated.     

Breast and Chest Size: Ideals and Stereotypes Through the 1990s

This study investigated differences in ideals and stereotypes associated with breast and chest size through the 1990s. Five cohorts of primarily Caucasian participants between 1990 and 1998 completed the Breast/Chest Rating Scale that consists of figures of men and women of varying upper torso sizes and a series of questions related to ideal size, perceptions of others' ideals, and characteristics associated with different sizes. Although the breast size women perceive as preferred by others has increased, the ideal breast size has remained stable for men and women. Men's ideal breast size was consistently larger than the breast size women prefer, and men also preferred a significantly larger chest size. Despite an increasing cultural emphasis on large chest size, there was a significant decrease in the chest size preferred by women across cohort groups. The chest size men think women prefer, however, has increased. Although there was little evidence of changes in stereotypes associated with chest size, the breast size associated with a variety of positive characteristics was significantly larger in 1998 than in 1992. These results are discussed in relation to body image and social implications.     

Erroneous knowledge of results affects decision and memory processes on timing tasks

On mental timing tasks, erroneous knowledge of results (KR) leads to incorrect performance accompanied by the subjective judgment of accurate performance. Using the start-stop technique (an analogue of the peak interval procedure) with both reproduction and production timing tasks, the authors analyze what processes erroneous KR alters. KR provides guidance (performance error information) that lowers decision thresholds. Erroneous KR also provides targeting information that alters response durations proportionately to the magnitude of the feedback error. On the production task, this shift results from changes in the reference memory, whereas on the reproduction task this shift results from changes in the decision threshold for responding. The idea that erroneous KR can alter different cognitive processes on related tasks is supported by the authors' demonstration that the learned strategies can transfer from the reproduction task to the production task but not visa versa. Thus effects of KR are both task and context dependent.     

Looking at the sunny side of life: age-related change in an event-related potential measure of the negativity bias

Studies of the negativity bias have demonstrated that negative information has a stronger influence than positive information in a wide range of cognitive domains. At odds with this literature is extensive work now documenting emotional and motivational shifts that result in a positivity effect in older adults. It remains unclear, however, whether this age-related positivity effect results from increases in processing of positive information or from decreases in processing of negative information. Also unknown is the specific time course of development from a negative bias to an apparently positive one. The present study was designed to investigate the negativity bias across the life span using an event-related potential measure of responding to emotionally valenced images. The results suggest that neural reactivity to negative images declines linearly with age, but responding to positive images is surprisingly age invariant across most of the adult life span.     

Using a computer simulation of three slot machines to investigate a gambler’s preference among varying densities of near-miss alternatives

The present article describes a software program in Visual Basic .NET designed to simulate three slot machines on a computer screen. This software is described in detail regarding utility, downloading, and usage; and data are presented illustrating the software’s potential for researchers interested in gambling behavior. A simulation of multiple slot machines such as this enables researchers to evaluate players’ preferences across various machines. In the highlighted experiment, 18 recreational slot machine players played the software for extra course credit and a chance at cash prizes. All participants played a version of the simulation in which every 5th response on average was a win, whereas the remaining trials were a loss. However, on those loss trials, a varying distribution of almost wins or near misses (i.e., two winning symbols on the payoff line and the final winning symbol directly above or below the payoff line) were presented in percentages of 15, 30, or 45. While no preferences across the three options could be predicted on the basis of reinforcement history alone, deviations from equal choices across the games were noted and appeared to be the result of the presentations of near-miss losing trials. Implications for a greater understanding of pathological gambling are presented.     

Expanding retrieval practice: an effective aid to preschool children's learning

The benefits of expanding retrieval practice for preschool children were explored in two experiments. In Experiment 1, three groups learned names for six plush toy pigs using expanding retrieval practice, a reward incentive, or a control condition. Reward did not significantly improve learning but retrieval practice doubled recall. In Experiment 2, three groups learned names to soft toys, comparing recall following massed elaborative study with either expanding retrieval practice or expanding re-presentation. Recall was tested after 1 minute, 1 day, and 2 days. A very large effect size (d = 1.9) indicated the very considerable benefit from expanding retrieval practice over the elaboration condition. Comparison with the re-presentation condition suggested that half of the benefit of expanding retrieval practice came from spaced scheduling and half from retrieval practice. Expanding retrieval practice provides an effective method to improve learning by young children.     

Determinants of Depression Severity and Duration in Canadian Adults: The Moderating Effects of Gender and Social Support

This study examined the effects of 4 subtypes of social support (tangible, affective, positive social interaction, and emotional/informational) and gender on the severity and duration of depressive symptoms within the general adult Canadian population. Data were collected from the Canadian Community Health Survey (CCHS; Statistics Canada, 2002 ). Upon meeting predetermined criteria, 6,316 participants were included in the study. The findings suggest that, overall, positive social interaction was significantly associated with decreases in depression severity; while emotional/informational support was significantly associated with increases in depression severity. Positive social interaction and emotional/informational support appeared to significantly decrease the duration of depression. Interesting gender differences also emerged among the 4 subtypes of social support. Implications of the findings are discussed.