The acquisition of bimanual coordination is mediated by anisotropic coupling between the hands

The present study was designed to test two predictions from the coupled oscillator model of multifrequency coordination. First, it was predicted that multifrequency tasks that match the inherent manual asymmetry (i.e., the preferred hand assigned to the faster tempo) would be easier to learn than tasks that do not match the inherent dynamics (i.e., the non-preferred hand assigned to the faster tempo). Second, in the latter case acquisition of the multifrequency coordination would involve a reorganisation of the coupling dynamics such that the faster hand would exert a greater influence on the slower hand than vice versa. Sixteen right-handed volunteers received extensive training on a 2:1 coordination pattern involving a bimanual forearm pronation-supination task. Participants were randomly assigned to one of two groups: 1L:2R in which the preferred right hand performed the higher frequency, or 2L:1R in which the non-preferred left hand performed the higher frequency. The dynamic stability of the patterns was assessed by the ability of participants to maintain the coordination pattern as movement frequency was increased. Changes in the directional coupling between the hands was assessed by transition pathways and lead-lag relationship evident in a 1:1 anti-phase frequency-scaled coordination task performed prior to and following three practice sessions of the 2:1 task. The predicted differential stability between the multifrequency patterns was evident in the initial acquisition sessions but by the end of training the two patterns evidenced equivalent stability. Unexpectedly, for both groups the fast hand displayed greater variability in amplitude and movement frequency than the slow hand perhaps reflecting anchoring afforded to the slow hand by synchronising movement endpoints with the auditory pacing metronome. Analysis of pre- to post-training changes to the coupling dynamics in the 1:1 anti-phase task support the hypothesis that acquisition of the 2L:1R pattern involved reorganisation of the inherent dynamics.     

A basis for bias in geographical judgments

To determine why North Americans tend to locate European cities south of North American cities at similar latitudes (Tversky, 1981), we had observers provide bearing estimates between cities in the U.S. and Europe. Earlier research using latitude estimates of these cities has indicated that each continent has several subjective regions (Friedman & Brown, 2000a). Participants judged cities from two subjectively northern regions (Milwaukee-Munich), two subjectively southern regions (Memphis-Lisbon), and the two "crossed" regions (Albuquerque-Geneva; Minneapolis-Rome). Estimates were biased only when cities from the subjectively northern regions of North America were paired with cities from the subjectively southern region of Europe. In contrast to the view that biases are derived from distorted or aligned map-like representations, the data provide evidence that the subjective representation of global geography is principally categorical. Biases in numerical location estimates of individual cities and in bearing estimates between city pairs are derived from plausible reasoning processes operating on the same categorical representations.     

The personal-group discrepancy: Is there a common information basis for personal and group judgment?

In contrast to motivational accounts of the personal-group discrepancy, results from this article suggest that the discrepancy is explained by aggregating different sets of comparison outcomes for either personal or group ratings. Results from a longitudinal study with East German (the minority group) and West German (the majority group) samples confirm the personal-group discrepancy and support our approach. First, social comparisons influenced evaluations of economic situation at both group and personal levels. Second, ratings of group versus personal economic situation were based on different sets of comparisons. Third, the mean structure of both sets of comparison outcomes mirrored the personal-group discrepancy. Fourth, an interaction between personal-group discrepancy and group status supported the authors' suggestions-concerning the direction of the discrepancy.     

Predictors of first onset and recurrence of major depression in young women during the 5 years following high school graduation

Although most depressive episodes in adulthood are recurrences of the disorder, lifetime history of major depression (MD) is often neglected in predictive models. On the basis of research and theory suggesting differential prediction of MD across the course of the disorder, the authors explored whether factors that predict a first MD onset would not predict MD recurrence. Predictors of MD were examined longitudinally in a sample of 128 young women followed for 5 years. Controlling for lifetime MD history, 5-year MD was predicted by the presence before study entry of 3 variables: having witnessed family violence before age 16, having a parent with a psychiatric disorder, and having a nonmood Axis I disorder. During the follow-up period, chronic and episodic stress predicted MD. Prior lifetime MD interacted with both chronic stress and parental psychopathology to predict MD, such that first onsets, but not recurrences, were predicted by these risk variables.     

The fast and the slow of skilled bimanual rhythm production: parallel versus integrated timing

Professional pianists performed 2 bimanual rhythms at a wide range of different tempos. The polyrhythmic task required the combination of 2 isochronous sequences (3 against 4) between the hands; in the syncopated rhythm task successive keystrokes formed intervals of identical (isochronous) durations. At slower tempos, pianists relied on integrated timing control merging successive intervals between the hands into a common reference frame. A timer-motor model is proposed based on the concepts of rate fluctuation and the distinction between target specification and timekeeper execution processes as a quantitative account of performance at slow tempos. At rapid rates expert pianists used hand-independent, parallel timing control. In alternative to a model based on a single central clock, findings support a model of flexible control structures with multiple timekeepers that can work in parallel to accommodate specific task constraints.