Children’s solutions of logical versus empirical problems: What’s missing and what develops?

This research examined the development of the ability to differentiate logical from empirical problems and the different ways in which children solve these problems. Thirty-two 4- and 5-year-olds, thirty-four 8- and 9-year-olds, and thirty-five 11- and 12-year-olds were given five questions regarding an imaginary character’s predictions as to where a ball would land after being dropped through a ‘tautology machine’. The questions examined encoding and recall of problems, children’s understanding of when evidence was necessary, and children’s evaluation of form and evidence. Data were analyzed in two ways: (1) by comparing differences across participants on component questions and (2) an individual analysis examining the consistency of responses to component questions across the problem set. Overall, the results indicated that: (1) sixth graders tended to differentiate logical from empirical problems while preschool and third grade children rarely did; (2) young children tend to ignore both the logical connective and the second half of problems-termed a ‘cut;’ (3) these cuts are less frequent when a problem is compatible with one empirical possibility; (4) cuts do not stem from encoding or recall errors, but seem to be the product of incomplete problem processing and (5) from third to sixth grade, children’s understanding of logical form increased as the rate of cuts decreased.     

Reproducibility and variability of the cost functions reconstructed from experimental recordings in multifinger prehension

The study examines whether the cost functions reconstructed from experimental recordings are reproducible over time. Participants repeated the trials on three days. By following Analytical Inverse Optimization procedures, the cost functions of finger forces were reconstructed for each day. The cost functions were found to be reproducible over time: application of a cost function C(i) to the data of Day j (i≠j) resulted in smaller deviations from the experimental observations than using other commonly used cost functions. Other findings are: (a) the 2nd order coefficients of the cost function showed negative linear relations with finger force magnitudes; (b) the finger forces were distributed on a 2-dimensional plane in the 4-dimensional finger force space for all subjects and all testing sessions; (c) the data agreed well with the principle of superposition, i.e. the action of object prehension can be decoupled into the control of rotational equilibrium and slipping prevention.     

Carrot eaters or moving heads: inductive inference is better supported by salient features than by category labels

How do words affect generalization, and how do these effects change during development? One theory posits that even early in development, linguistic labels function as category markers and thus are different from the features of the stimuli they represent. Another theory holds that early in development, labels are akin to other features, but that they may become category markers in the course of development. We addressed this issue in two experiments with 4- to 5-year-olds and adults. In both experiments, participants performed a categorization task (in which they predicted a category label) and an induction task (in which they predicted a missing feature). In the latter task, the category label was pitted against a highly salient feature, such that reliance on the label and reliance on the salient feature would result in different patterns of responses. Results indicated that children relied on the salient feature when performing induction, whereas many adults relied on the category label. These results suggest that early in development, labels are no more than features, but that they may become category markers in the course of development.     

Directional variability of the isometric force vector produced by the human hand in multijoint planar tasks

Numerous studies have examined control of force magnitude, but relatively little research has considered force direction control. The subjects applied isometric forces to a handle and the authors compared within-trial variability when force is produced in different directions. The standard deviation of the force parallel to the prescribed direction of force production increased linearly with the targeted force level, as did the standard deviation of the force perpendicular to the instructed direction. In contrast, the standard deviation of the angle of force production decreased with increased force level. In the 4 (of 8) instructed force directions where the endpoint force was generated due to a joint torque in only 1 joint (either the shoulder or elbow) the principal component axes in force space were well aligned with the prescribed direction of force production. In the other directions, the variance was approximately equal along the 2 force axes. The variance explained by the first principal component was significantly larger in torque space compared to the force space, and mostly corresponded to positive correlation between the joint torques. Such coordinated changes suggest that the torque variability was mainly due to the variability of the common drive to the muscles serving 2 joints, although this statement needs to be supported by direct studies of muscle activation in the future.     

Physical health and social network characteristics as determinants of mental health across cultures

This study examines cross-cultural differences in the etiology of depression and anxiety, two common indicators of mental health problems. Using an ethnically diverse sample of 162 college students, we found that chronic physical symptoms and social network characteristics, particularly network quality, were predictive of both depression and anxiety, yet their effects were mediated by ethnicity. Multiple regression analyses showed that social network quality, compared to physical health, was a much stronger predictor of mental health in Caucasian students, whereas among students of Asian/Pacific descent, physical health was a much stronger predictor of mental health than the social network characteristics. The observed differences were particularly strong for anxiety, which was not significantly associated with physical health in Caucasian students or social network size and quality in the Asian/Pacific group. Theoretical and clinical implications of the results are discussed.     

Physical health and social network characteristics as determinants of mental health across cultures

This study examines cross-cultural differences in the etiology of depression and anxiety, two common indicators of mental health problems. Using an ethnically diverse sample of 162 college students, we found that chronic physical symptoms and social network characteristics, particularly network quality, were predictive of both depression and anxiety, yet their effects were mediated by ethnicity. Multiple regression analyses showed that social network quality, compared to physical health, was a much stronger predictor of mental health in Caucasian students, whereas among students of Asian/Pacific descent, physical health was a much stronger predictor of mental health than the social network characteristics. The observed differences were particularly strong for anxiety, which was not significantly associated with physical health in Caucasian students or social network size and quality in the Asian/Pacific group. Theoretical and clinical implications of the results are discussed.     

Effects of joint immobilization on standing balance

We investigated the effect of joint immobilization on the postural sway during quiet standing. We hypothesized that the center of pressure (COP), rambling, and trembling trajectories would be affected by joint immobilization. Ten young adults stood on a force plate during 60 s without and with immobilized joints (only knees constrained, CK; knees and hips, CH; and knees, hips, and trunk, CT), with their eyes open (OE) or closed (CE). The root mean square deviation (RMS, the standard deviation from the mean) and mean speed of COP, rambling, and trembling trajectories in the anterior–posterior and medial–lateral directions were analyzed. Similar effects of vision were observed for both directions: larger amplitudes for all variables were observed in the CE condition. In the anterior–posterior direction, postural sway increased only when the knees, hips, and trunk were immobilized. For the medial–lateral direction, the RMS and the mean speed of the COP, rambling, and trembling displacements decreased after immobilization of knees and hips and knees, hips, and trunk. These findings indicate that the single inverted pendulum model is unable to completely explain the processes involved in the control of the quiet upright stance in the anterior–posterior and medial–lateral directions.