The role of perceptual similarity of the task environments in children’s perseverative responding

Perseverative responding is often seen in children’s performance in a variety of contexts. One such context is symbolic comprehension in which 2- and 2½-year-olds demonstrate difficulty in appreciating the association of symbols (pictures and scale models) and their referents and show a high proportion of perseverative responding. Representational-level explanations of perseveration were explored in the current studies via examination of the impact of perceptual similarity of visual environments across trials. Across two experiments, children saw either a picture (Experiment 1) or a scale model (Experiment 2) of a hiding location of a room and were then encouraged to recover the toy from an identical room. Manipulating the perceptual similarity of the environments across successive trials affected performance and perseverative responding. These results highlight the critical role played by perceptual information not only in symbolic tasks but also in many other tasks and have important implications for theories of perseveration.     

Tests of the Relationship Between Children's Temperament and Asthma and of the Reliability and Validity of the Brief Scale of Temperament

Two studies are reported. One examined the reliability and validity of a brief scale to measure children's temperament; the other tested the relationship of early temperament and the development of asthma. In Study 1, principal caretakers of 46 4- to 7-year-olds, usually the mothers, filled out questionnaires containing the Brief Scale of Temperament (BST) and the Behavioral Style Questionnaire. The caretakers did this twice, about 1 week apart. The first time the children's recent temperament was assessed, and the second time past (> 1 year) temperament was assessed. Internal consistency and correlational analyses revealed substantial reliability and validity for BST assessments of recent and past temperament. Study 2 incorporated the BST in a large-scale survey of 325 families, with parents providing data on their children's asthma and temperament. BST assessments of early (past) temperament were made retrospectively regarding the child's first few years. Comparisons of early temperament revealed no differences between children who developed asthma and those who did not in their overall scores on the BST or for any of the temperament characteristics it measures. In addition, correlational analyses of data for asthmatics showed that early temperament was not related to ratings of the severity of the asthma condition the children developed or the impacts of any of 12 specific asthma triggers, including any involving emotional states, such as stress or worry.     

Individual Differences in Child Kaleidoblock Responses

The relationship between self-esteem and parental identification was investigated. The hypothesis that self-esteem is positively correlated with parental identification was supported for female college students by two out of three self-esteem measures. For male subjects one social self-esteem measure correlated negatively with maternal identification and a self-concept measure correlated positively. No relationship between self-esteem and paternal identification existed for males: hence the hypothesis was refuted. The importance of social self-esteem in the feminine self-concept and its basis in parental identification is emphasized in the discussion.     

Perceptual-Motor Contributions to Static and Dynamic Balance Control in Children

The authors addressed balance control in children from the perspective of skill development and examined the relationship between specific perceptual and motor skills and static and dynamic balance performance. Fifty 11- to 13-year-old children performed a series of 1-legged balance tasks while standing on a force platform. Postural control was reflected in the maximum displacement of the center of mass in anterior-posterior and mediolateral directions. Simple visual, discrimination, and choice reaction times; sustained attention; visuomotor coordination; kinesthesis; and depth perception were also assessed in a series of perceptual and motor tests. The correlation analysis revealed that balancing under static conditions was strongly associated with the ability to perceive and process visual information, which is important for feedback-based control of balance. On the other hand, when greater task demands were imposed on the system under dynamic balancing conditions, the ability to respond to the destabilizing hip abductions-adductions in order to maintain equilibrium was associated with motor response speed, suggesting the use of a descending, feedforward control strategy. Therefore, like adults, 11- to 13-year-old children have the ability to select varying balance strategies (feedback, feedforward, or both), depending on the constraints of a particular task.     

Strategie Calibration and Spatial Alignment: A Model From Prism Adaptation

Two types of adaptive processes involved in prism adaptation have been identified: slower spatial realignment among the several unique sensorimotor coordinate systems (spatial maps) and faster strategic motor control responses (including skill learning and calibration) to spatial misalignment. One measures the 1st process by assessing the aftereffects of prism exposure, whereas direct effects of the prism during exposure are a measure of the 2nd process. A model is described that relates those adaptive processes and distinguishes between extraordinary alignment and ordinary calibration. A conformal translation algorithm that operates on the hypothesized circuitry is proposed. The authors apply the model to explain the advantage of visual calibration when the limb is seen in the starting position prior to movement initiation. Implications of the model for the use of prism adaptation as a tool for investigation of motor control and learning are discussed.     

Variability and Determinism in Motor Behavior

In investigations into perception-action systems, variability of observable behavior may be considered to (a) interfere with inquiry, (b) be neither detrimental nor particularly useful to inquiry, or (c) play a crucial role in inquiry. The authors underscore recent suggestions that alternative (c) is a preferred strategy for the study of many motor behaviors. In tutorial fashion, the authors review the concepts of variability and determinism with respect to postural and rhythmic movements. Study of the variability of those behaviors has revealed crucial features suggestive of underlying mechanisms and control, such as particular blends of noise and determinism (piecewise determinism). It has also revealed general lessons (for example, more variable does not mean more random and more controllable does not mean more deterministic) that may extend to other classes of perceptual-motor behavior.     

Effect of Age and Gender in the Control of Elbow Flexion Movements

In previous studies of rapid elbow movements in young healthy men, characteristic task-dependent changes in the patterns of muscle activation when movement speed or distance was varied have been reported. In the present study, the authors investigated whether age or gender is associated with changes in the patterns of muscle activity previously reported in young men. Arm movements of 10 healthy older and 10 healthy younger participants (5 men and 5 women in each group) were studied. Surface electromyograms (EMGs) from agonist (biceps) and antagonist (triceps) muscles, kinematic and kinetic parameters, as well as anthropometric and strength measures were recorded. All 4 groups of participants showed similar task- (distance or speed) dependent changes in biphasic EMG activity. Similar modulation of the initial rate of rise of the EMG, integrated agonist and antagonist EMG activity, as well as their relative timing were observed in all 4 groups. Those results suggest that older individuals of both genders retain the control strategies for elbow movements used by young individuals. Despite the qualitative similarities in the patterns of muscle activation, the men moved more quickly than the women, and younger participants moved more quickly than older participants. Those performance differences could not be explained in terms of differences in body size and strength alone.     

Monocular and Binocular Vision in the Control of Goal-Directed Movement

In the present research the authors examined the time course of binocular integration in goal-directed aiming and grasping. With liquid-crystal goggles, the authors manipulated vision independently to the right and left eyes of 10 students during movement preparation and movement execution. Contrary to earlier findings reported in catching experiments (I. Olivier, D. J. Weeks, K. L. Ricker, J. Lyons, & D. Elliott, 1998), neither a temporal nor a spatial binocular advantage was obtained in 1 grasping and 2 aiming studies. That result suggests that, at least in some circumstances, monocular vision is sufficient for the precise control of limb movements. In a final aiming experiment involving 3-dimen- sional spatial variability and no trial-to-trial visual feedback about performance, binocular vision was associated with greater spatial accuracy. Binocular superiority appeared to be most pronounced when participants were unable to adjust their limb control strategy or procedure on the basis of terminal feedback about performance.     

Development of Postural Adjustment During Gait Initiation: Kinematic and EMG Analysis

The authors studied the development of postural adjustments associated with the initiation of gait in children by using kinematic and electromyographic (EMG) analysis. Participants (N = 28) included infants with 1-4 and 9-17 months of walking experience, children 4-5 years of age, and adults. Anticipatory postural adjustments (APA) were present in the youngest age groups, including a clear anticipatory lateral tilt of the pelvis and the stance leg, which enabled the child to unload the opposite leg shortly before its swing phase. An anticipatory activation of the hip abductor of the leg in stance phase prior to heel-off was found, suggesting pelvis stabilization. APA did not appear consistently until 4-5 years of age. A decrease in segmental oscillations occurred across the ages, indicating better control of intersegmental coordination in the frontal and sagittal planes during the postural phase of gait initiation. Young walkers presented APA involving movements of both the upper and the lower parts of the body, whereas, like adults, 4- to 5-year-olds were able to laterally shift only the pelvis and the stance leg. The oldest children and the adults also showed lower activation levels of hip and knee muscles but higher activation at the ankle level. Those kinematic and EMG results taken together suggest a clear developmental sequence from an en bloc operation of the body through an articulated operation with maturation, walking experience, or both.     

Center of Gravity Motions and Ankle Joint Stiffness Control in Upright Undisturbed Stance Modeled Through a Fractional Brownian Motion Framework

The authors modeled the center of gravity vertical projection (CG_V) and the difference, CP - CG_V, which, combined, constitute the center of pressure (CP) trajectory, as fractional Brownian motion in order to investigate their relative contributions and t heir spatiotemporal articulation. The results demonstrated that CG_V and CP - CG_V motions are both endowed in complementary tashion with strong stochastic and part-deterministic behaviors. In addition, if the temporal coordinates remain similar for all 3 trajectories by definition, the switch between the successive control mechanisms appears for shorter displacements for CP - CG_V and CG_V than for CP trajectories. Results deduced from both input (CG,) and muscular stiffness (CP - CG_V) thus provide insight into the way the central nervous system regulates stance control and in particular how CG and CP - CG are controlled.