On discontinuities in motor learning: a longitudinal study of complex skill acquisition on a ski-simulator

The qualitative behavioral reorganizations that occurred during the acquisition of a complex motor skill were examined. Five novice participants practiced for 39 sessions of ten 1-min trials on a modified version of the ski-simulator. Analyses focused on the motion of the apparatus platform, modeled as a self-sustained oscillator. At the beginning of the experiment, all participants adopted a behavior that could be modeled with a highly nonlinear stiffness function and a Rayleigh damping function. The behavior in the final part of the experiment was captured by a qualitatively different model, with a linear stiffness function and a van der Pol damping behavior. The transition from the initial to the final model was gradual and was marked in most cases by an abrupt increase of oscillation frequency. During the transition stage, the 2 damping behaviors seemed alternately exploited within each trial. The results are discussed in the framework of the dynamical systems approach to motor coordination and learning, considering motor skill acquisition as a phase transition.     

An approach for practice administration and interpretation of the MMPI-2

This paper discusses one teaching approach for practice administration and interpretation of the MMPI-2 in a graduate course on personality assessment. After graduate students practice scoring and interpreting the MMPI-2 inventory completed with specific response sets and practice interpreting MMPI-2 profiles of cases prepared for teaching and practice in interpretation, students practice administering and interpreting the MMPI-2 for volunteer test-takers who complete the inventory with a simulated stress response set. The simulated stress response set approach may be helpful in providing skill-building practice in the early phases of learning the MMPI-2 with volunteer test-takers, while minimizing some of the ethical concerns raised regarding actual administrations with nonclient volunteers in the early phases of training in assessment.     

Pragmatic communication skills in patients with Parkinson's disease

BACKGROUND: Pragmatic communication abilities may depend on intact frontal lobe systems. Independent evidence suggests that some persons with Parkinson's disease (PD) are impaired on measures of frontal lobe function. HYPOTHESIS: We therefore hypothesized in Study 1 that pragmatic communication skills would be impaired in some persons with PD and would be linked to frontal dysfunction in these patients. In Study 2 we hypothesized that PD patients would be unaware of their pragmatic communication deficits. METHODS: In Study 1 we administered tests of pragmatic abilities and frontal lobe functioning to twenty-two persons with Parkinson's disease (PD) and 10 healthy controls. In Study 2 we obtained self-ratings of pragmatic abilities from 11 PD patients and then checked these self-ratings against ratings of these same abilities by the patient's spouses. RESULTS: We found in Study 1 that patients with PD were: (a) significantly impaired on measures of pragmatic communication abilities, especially in the areas of conversational appropriateness, turn-taking, prosodics and proxemics, and that this impairment was significantly related to measures of frontal lobe function. In study 2 we found that PD patients overestimated their own abilities relative to spousal ratings of those abilities and thus were unaware of the extent of their problems with pragmatic social communication skills. CONCLUSION: We conclude that pragmatic social communication skills are impaired in PD and that this impairment may be related to frontal lobe dysfunction.     

Experimental tests of an attitudinal theory of the gender gap in voting

This research examined the hypothesis that gender gaps in voting stem from differences in the extent to which men and women agree with candidates' issue stances. Two initial experiments portraying candidates by their sex and attitudes and a third experiment that also included information about political party produced the predicted attitudinal gender-congeniality effect: Participants of each sex reported greater likelihood, compared with participants of the other sex, of voting for the candidate who endorsed positions typically favored more by their own sex than the other sex. In addition, this gender-congeniality effect was present among Republican and independent participants but absent among Democratic participants because Democratic men as well as women favored candidates who advocated the positions typically favored by women. Interpretation invoked the importance of group interest based on gender as an influence on women's voting.     

Modulation of tremor amplitude during deep brain stimulation at different frequencies

Rest tremor was quantified in the index finger tip of 16 patients with Parkinson's disease (PD) receiving deep brain stimulation (DBS) of the ventro-intermediate nucleus (Vim) of the thalamus, the subthalamic nucleus (STN), or the internal part of the globus pallidus (GPi) while being off L-dopa for 12h. Clinically, without DBS, tremor amplitude varied from absent to high. Tremor was recorded continuously for about 5 min under three conditions of DBS repeated twice, namely, effective frequency (E), ineffective frequency (I), and no DBS (O). No changes in tremor were observed across conditions in subjects with little or no tremor. However, in subjects with moderate to large amplitude tremor, DBS decreased tremor amplitude to near normal values within a few seconds. Generally, transitions were progressive and occurred with a varying time delay. Occasionally, tremor escaped from control regardless of the stimulation condition considered. In some cases tremor amplitude in one condition appeared to depend on the preceding condition. Finally, the results were reproducible on two consecutive days. We conclude that tremor control with DBS follows specific dynamical rules, which must be compatible with the hypotheses proposed regarding the underlying mechanisms of DBS.     

Uncertainty in pigeons

Pigeons classified a display of illuminated pixels on a touchscreen as sparse or dense. Correct responses were reinforced with six food pellets; incorrect responses were unreinforced. On some trials an uncertain response option was available. Pecking it was always reinforced with an intermediate number of pellets. Like monkeys and people in related experiments, the birds chose the uncertain response most often when the stimulus presented was difficult to classify correctly, but in other respects their behavior was not functionally similar to human behavior based on conscious uncertainty or to the behavior of monkeys in comparable experiments. Our data were well described by a signal detection model that assumed that the birds were maximizing perceived reward in a consistent way across all the experimental conditions.     

A cross-modal interference effect in grasping objects

The aim of the present paper was to investigate how the kinematics of a hand reaching toward a visual target would be influenced by haptic and proprioceptive input from an unseen distractor actively grasped in the other, nonreaching hand. The main results were that the amplitude of maximum grip aperture was smaller and the time to maximum grip aperture was earlier when the distractor was smaller than the target. The interference effect from the distractor was similar for both hands as they reached. Furthermore, results from a vibrating-distractor condition for passive tactile input revealed that the interference effects were evident only when the distractor was actively grasped. We suggest that neural processing of proprioceptive and tactile information relevant to distractor size produced the observed interference effects. We also emphasize the importance of active manipulation of the distractor stimulus in eliciting such interference effects.     

Strategic aspects of numerosity judgment: the effect of task characteristics

In previous investigations we documented that people use several strategies to determine different numerosities of blocks that are presented in a square grid. One of these strategies is the clever subtraction strategy, wherein the number of empty squares in the grid is subtracted from the total number of squares in the grid. In the present study we investigated participants' flexibility in strategy use when varying the shape of the grid. Analysis of the results in terms of the theoretical framework of Lemaire and Siegler (1995) regarding strategic change shows that this contextual variable affected the frequency, execution time, and accuracy of subjects' use of the subtraction strategy. The usefulness of this framework for analyzing the nature of the adaptation to contextual variations is discussed. From a methodological point of view, this study documents the potential of Beem's (1993, 1999) segmented linear regression models for assessing subjects' strategy use in cognitive tasks.