Different visuomotor processes maturation rates in children support dual visuomotor learning systems

Different processes are involved during visuomotor learning, including an error-based procedural and a strategy based cognitive mechanism. Our objective was to analyze if the changes in the adaptation or the aftereffect components of visuomotor learning measured across development, reflected different maturation rates of the aforementioned mechanisms. Ninety-five healthy children aged 4–12 years and a group of young adults participated in a wedge prism and a dove prism throwing task, which laterally displace or horizontally reverse the visual field respectively. The results show that despite the age-related differences in motor control, all children groups adapted in the error-based wedge prisms condition. However, when removing the prism, small children showed a slower aftereffects extinction rate. On the strategy-based visual reversing task only the older children group reached adult-like levels. These results are consistent with the idea of different mechanisms with asynchronous maturation rates participating during visuomotor learning.     

Kids observing other kids' hands: visuomotor priming in children

We investigated motor resonance in children using a priming paradigm. Participants were asked to judge the weight of an object shortly primed by a hand in an action-related posture (grasp) or a non action-related one (fist). The hand prime could belong to a child or to an adult. We found faster response times when the object was preceded by a grasp hand posture (motor resonance effect). More crucially, participants were faster when the prime was a child's hand, suggesting that it could belong to their body schema, particularly when the child's hand was followed by a light object (motor simulation effect). A control experiment helped us to clarify the role of the hand prime. To our knowledge this is the first behavioral evidence of motor simulation and motor resonance in children. Implications of the results for the development of the sense of body ownership and for conceptual development are discussed.     

Response coding and visuomotor transformation in the Simon task: the role of action goals

Manual responses can be defined by differing response parameters. Any of them may generate a Simon effect. For all those response parameters, the same implementation of the Simon effect (in terms of subserving mechanism) is assumed. In 3 experiments, subjects had to respond with either fingers or sticks. Temporal properties of the Simon effect changed with response parameters relevant in a task. The Simon effect for manual responses decayed. For stick responses, in which the action goal differed from the anatomical mapping of the acting hand, a sustained Simon effect was observed. However, if the action goal for stick responses was not instrumental for selecting the correct response, the Simon effect decayed. The findings are consistent with the notion of different mechanisms involved in generating a Simon effect.     

Practice effects on visuomotor and problem-solving tests by children

Practice effects on a visuomotor test (the Developmental Test of Visuo-Motor Integration), a timed visual discrimination test (the Underlining Test), and two problem-solving tests (the Porteus Mazes Test and the Tower of Hanoi Test) were analyzed. Children of two age groups (Ms: 7.7 and 11.6 yr.) were chosen to study the effect of age on practice effects. The tests were repeated nine times with test-retest intervals of 2 mo. The Developmental Test of Visuo-Motor Integration showed no practice effects, while the Porteus Mazes Test, the Underlining Test, and the Tower of Hanoi Test showed significant practice effects. Practice effects were larger for the older age group on all the tests, except the Developmental Test of Visuo-Motor Integration. The Developmental Test of Visuo-Motor Integration and the Underlining Test showed good reliability, but those of the problem-solving tasks were less satisfactory. The stability of all the tests, except the Tower of Hanoi Test, was good.     

Interlimb differences in visuomotor and dynamic adaptation during targeted reaching in children

While a number of studies have focused on movement (a)symmetries between the arms in adults, less is known about movement asymmetries in typically developing children. The goal of this study was to examine interlimb differences in children when adapting to novel visuomotor and dynamic conditions while performing a center-out reaching task. We tested 13 right-handed children aged 9–11 years old. Prior to movement, one of eight targets arranged radially around the start position was randomly displayed. Movements were made either with the right (dominant) arm or the left (nondominant) arm. The children participated in two experiments separated by at least one week. In one experiment, subjects were exposed to a rotated visual display (30° about the start circle); and in the other, a 1 kg mass (attached eccentrically to the forearm axis). Each experiment consisted of three blocks: pre-exposure, exposure and post-exposure. Three measures of task performance were calculated from hand trajectory data: hand-path deviation from the straight target line, direction error at peak velocity and final position error. Results showed that during visuomotor adaptation, no interlimb differences were observed for any of the three measures. During dynamic adaptation, however, a significant difference between the arms was observed at the first cycle during dynamic adaptation. With regard to the aftereffects observed during the post-exposure block, direction error data indicate considerably large aftereffects for both arms during visuomotor adaptation; and there was a significant difference between the arms, resulting in substantially larger aftereffects for the right arm. Similarly, dynamic adaptation results also showed a significant difference between the arms; and post hoc analyses indicated that aftereffects were present only for the right arm. Collectively, these findings indicate that the dominant arm advantage for developing an internal model associated with a novel visuomotor or dynamic transform, as previously shown in young adults, may already be apparent at 9 to 11-year old children.     

Catching sight of children with internalizing symptoms in upper elementary classrooms

Teachers play a crucial role in the assessment of children's internalizing symptoms but may not always succeed in accurately identifying such symptoms in class. Using a multilevel structural equation modeling (MSEM) approach, this study aimed to explore teacher and child characteristics that may explain measurement bias in teachers' ratings of internalizing symptoms at the between- and within-teacher level. Upper elementary school teachers (N = 92, 74.9% female) filled out the Strengths and Difficulties Questionnaire, Student-Teacher Relationship Scale, and Student-Specific Teacher Self-Efficacy Scale for randomly selected children (N = 690, 50.5% girls, Grades 3–6) from their classrooms. Participating teachers and children also responded to several background questions. Multilevel SEMs suggested that teachers' self-efficacy beliefs toward, relationship experiences with, and externalizing symptom ratings of individual children affected their ratings of these children's internalizing symptoms at the within-teacher level. Specifically, given equal levels of internalizing behavior, teachers were likely to systematically under-identify symptoms of anxiety and over-identify bullying for children with more externalizing behavior and conflictual relationships, or in circumstances where teachers had lower self-efficacy. Children with high levels of closeness received systematically higher ratings on somatic complaints and lower ratings on solitary behavior and peer problems. At the between-teacher level, less experienced teachers were more likely to over-identify symptoms of worries than were more experienced teachers, given equal levels of internalizing symptoms. As such, these findings extend the limited body of evidence on children's internalizing symptoms in upper elementary school.     

Nonlinear visuomotor transformations: Locus and modularity

Participants in two experiments moved a mouse-like device to the right to move a cursor on a computer screen to a target position. The cursor was invisible during motion but reappeared at the end of each movement. The relationship between the amplitudes of the cursor movement and the mouse movement was exponential in Experiment 1 and logarithmic in Experiment 2 for two groups of participants, while it was linear for the control groups in both experiments. The results of both experiments indicate that participants adjusted well to the external transformation by developing an internal model that approximated the inverse of the external transformation. We introduce a method to determine the locus of the internal model. It indicates that the internal model works at a processing level that either preceded specification of movement amplitude, or had become part of movement amplitude specification. Limited awareness of the nonlinear mouse–cursor relationship and the fact that a working-memory task had little effect on performance suggest that the internal model is modular and not dependent on high-level cognitive processes.     

Catching skills in infancy

Infants were induced to reach for fast moving objects whose velocity and starting position varied. Altogether, 144 reaches were analyzed by a technique that took into consideration the three-dimensional properties of reaches. It was found that reaches in all conditions were aimed close to the meeting point with the object. The precision in timing of a reach was about a twentieth of a second, and the systematic timing errors were close to zero. The results suggest that the infant reaches in reference to a coordinate system fixed to the moving object instead of to the static background, that is, the infant's hand is moved with the object at the same time as it is moved toward the object. It is concluded that the capacity to time and coordinate one's movements in the catching of a moving object is a very basic and early developed skill.     

Nonlinear visuomotor transformations: locus and modularity

Participants in two experiments moved a mouse-like device to the right to move a cursor on a computer screen to a target position. The cursor was invisible during motion but reappeared at the end of each movement. The relationship between the amplitudes of the cursor movement and the mouse movement was exponential in Experiment 1 and logarithmic in Experiment 2 for two groups of participants, while it was linear for the control groups in both experiments. The results of both experiments indicate that participants adjusted well to the external transformation by developing an internal model that approximated the inverse of the external transformation. We introduce a method to determine the locus of the internal model. It indicates that the internal model works at a processing level that either preceded specification of movement amplitude, or had become part of movement amplitude specification. Limited awareness of the nonlinear mouse-cursor relationship and the fact that a working-memory task had little effect on performance suggest that the internal model is modular and not dependent on high-level cognitive processes.     

Abrupt, but not gradual visuomotor distortion facilitates adaptation in children with developmental coordination disorder

A previous experiment investigating visuomotor adaptation in typically developing children and children with Developmental Coordination Disorder (DCD) suggested poor adaptation to an abruptly induced visuomotor perturbation. In the current study, using a similar center-out drawing task, but administering either an abrupt or a gradual perturbation, and twice as many adaptation trials, we show that typically developing children are well able to successfully update an existing internal model in response to a 60 degrees rotation of the visual feedback, independent of the perturbation condition. Children with DCD, however, updated their internal map more effectively during exposure to an abrupt visuomotor perturbation than to a gradual one. This may suggest that the adaptation process in children with DCD responds differently to small vs. large steps of visuomotor discrepancies. Given the known role of the cerebellum in providing an error signal necessary for updating the internal model in response to a gradual visuomotor distortion, the results of our study add to the growing body of evidence implicating compromised cerebellar function in DCD.     

The visuomotor mental rotation task: visuomotor transformation times are reduced for small and perceptually familiar angles

In the visuomotor mental rotation (VMR) task, participants point to a location that deviates from a visual cue by a predetermined angle. This task elicits longer reaction times (RT) relative to tasks wherein the visual cue is spatially compatible with the movement goal. The authors previously reported that visuomotor transformations are faster and more efficient when VMR responses elicit a degree of dimensional overlap (i.e., 0° and 5°) or when the transformation involves a perceptually familiar angle (i.e., 90° or 180°; K. A. Neely & M. Heath, 2010b). One caveat to this finding is that standard and VMR responses were completed in separate blocks of trials. Thus, between-task differences not only reflect the temporal demands of the visuomotor transformations, but also reflect the temporal cost of response inhibition. The goal of this study was to isolate the time cost of visuomotor transformations in the VMR task. The results demonstrated that visuomotor transformations are more efficient and effective when the response entails a degree of dimensional overlap between target and response (i.e., when the angular disparity between the responses is small) or when the transformation angle is perceptually familiar.     

Dynamic visuomotor synchronization: Quantification of predictive timing

When a moving target is tracked visually, spatial and temporal predictions are used to circumvent the neural delay required for the visuomotor processing. In particular, the internally generated predictions must be synchronized with the external stimulus during continuous tracking. We examined the utility of a circular visual-tracking paradigm for assessment of predictive timing, using normal human subjects. Disruptions of gaze–target synchronization were associated with anticipatory saccades that caused the gaze to be temporarily ahead of the target along the circular trajectory. These anticipatory saccades indicated preserved spatial prediction but suggested impaired predictive timing. We quantified gaze–target synchronization with several indices, whose distributions across subjects were such that instances of extremely poor performance were identifiable outside the margin of error determined by test–retest measures. Because predictive timing is an important element of attention functioning, the visual-tracking paradigm and dynamic synchronization indices described here may be useful for attention assessment.     

Dynamic action in virtual environments: Constraints on the accessibility of action knowledge in children and adults

In a series of three experiments, we probed the accessibility of action knowledge in different versions of a virtual environment (VE) with 7-year-old children and adults. Using a PHANToM^TM haptic interface, participants performed a virtual throwing task in which they tried to propel a ball from a table to hit a target on the ground. In Experiments 1 and 2, the virtual scene was presented on a computer monitor, and, in Experiment 3, it was projected by using a video projector so that the vertical and horizontal dimensions and the spatial location of the VE corresponded to the real-world dimensions. Results indicate that action knowledge is accessible even in a nonimmersive VE, but also suggest that the need to recalibrate perceptual-motor mappings constrains the accessibility of this kind of intuitive knowledge.     

Interventions for children of divorce: toward greater integration of research and action.

A number of child-, family-, and system-focused interventions have been designed to prevent or reduce the negative effects of divorce on children. This article critically evaluates these intervention efforts by examining (a) their relation to basic research on the processes proposed to mediate children's postdivorce adjustment and (b) evaluation studies assessing the effectiveness of various programs. Although interventions address some of the factors proposed to mediate children's adaptation to divorce, the interplay between interventions and basic research on children's postdivorce adaptation is limited. Moreover, some intervention efforts appear to be beneficial, but most lack empirical documentation of their efficacy. This analysis leads to several recommendations for basic and applied research and for improving the response of the mental health field to the problems experienced by many children from divorcing families.     

Dynamic action in virtual environments: constraints on the accessibility of action knowledge in children and adults

In a series of three experiments, we probed the accessibility of action knowledge in different versions of a virtual environment (VE) with 7-year-old children and adults. Using a PHANToM haptic interface, participants performed a virtual throwing task in which they tried to propel a ball from a table to hit a target on the ground. In Experiments 1 and 2, the virtual scene was presented on a computer monitor, and, in Experiment 3, it was projected by using a video projector so that the vertical and horizontal dimensions and the spatial location of the VE corresponded to the real-world dimensions. Results indicate that action knowledge is accessible even in a nonimmersive VE, but also suggest that the need to recalibrate perceptual-motor mappings constrains the accessibility of this kind of intuitive knowledge.     

Unique behavioral strategies in visuomotor learning: Hope for the non-learner

The existence of individual differences in motor learning capability is well known but the behaviors or strategies that contribute to this variability have been vastly understudied. What performance characteristics distinguish an expert level performer from individuals who experience little to no success, those labeled non-learners? We designed a rule-based visuomotor task which requires identification (discovery) and then exploitation of specific explicit and implicit task components that requires a specific movement pattern, the task rule, for goal achievement. When participants first attempt the task, they are informed about the goal, but are naïve to the task rule. Therefore, the purpose of this experiment is to determine how acquisition of both implicit and explicit task components, the inherent elements of the task rule, reveals differing strategies associated with performance and task success. We test the hypothesis that an examination of performance will reveal sub-groups with varying levels of success. Further, for each subgroup, we expect to find a unique relationship between visual Time-in-Target feedback (a measure of success) and subsequent updating of each task component. Out of 32 non-disabled adults, we identified three distinct sub-groups: (Low Performer/Non-Learner (LP, N = 9), Moderate Performer (MP, N = 12) and High Performer (HP, N = 11)). A quantitative analysis of behavioral patterns reveals three findings: First, the LP sub-group demonstrated significantly lower task success which was associated with difficulty identifying the explicit component of the task. Second, the HP sub-group acquired the two task components in parallel over practice. Third, when both explicit and implicit component performance is plotted across sub-groups, a task component continuum emerges that seamlessly progresses from low to moderate to high performer groups. An exploratory analysis reveals that self-reported level of prior lifetime accumulation of video game and physical activity experience is a significant predictor of individual task performance (R² = 0.50). In summary, what appears to be a key distinction between varying levels of human rule-based motor learning is the process by which feedback is used to update performance of inherent elements of the task rule. Evidence of a performance continuum and limited prior experience suggests that Low Performer/Non-Learners are generally inexperienced with these kinds of tasks, although the role of genetics and other innate learning capabilities in visuomotor learning is still largely unknown. These findings provoke new research directions toward probing the differential performance strategies associated with expertise and the development of interventions aimed to convert non-learners into learners.     

Visuoperceptual and visuomotor deficits in developmental stutterers: an exploratory study

Although the cause of stuttering is unknown, there is strong evidence for it being a neuromotor disorder characterised by an abnormality of higher control encompassing not only speech but other motor systems. The aim of this exploratory study was to look for the presence of non-speech/language deficits--in particular, visuomotor and visuoperceptual deficits--in persons who stutter. Twelve moderate to severe developmental stutterers were compared with a group of fluent speakers, matched for age and sex, on a range of computerized sensory-motor tasks. These tasks covered various aspects of visuomotor function--ballistic movement, dynamic steadiness, and several types of tracking--and visuoperceptual function--acuity, static perception, and dynamic perception. A novel technique was used to remove the visuospatial component from tracking performance. Stutterers had slower reaction times, less accurate random tracking, and impaired dynamic visual perception. Severity of stuttering correlated with reaction time and dynamic perception. Removal of the visuoperceptual component from tracking performance indicated that the impaired tracking in the stutterers was predominantly due to reduced dynamic perception. This is the first study to provide preliminary evidence for the presence of non-linguistic visuoperceptual and upper-limb visuomotor tracking deficits in people with moderate to severe stuttering. These findings support a neurogenic aetiology for stuttering and are compatible with evidence of an overactive dopamine system in stutterers.     

Sex differences and effects of aging on visuomotor coordination.

The purpose of this study was to examine the effects of aging on men and women in processing information required to reproduce direction and distance on a visuomotor task. Subjects (45 men and 45 women) selected from three age groups (25-34 yr., 45-54 yr., 65-74 yr.) were required to estimate blindly the exact criterion location of a target-point they had identified under one of the following conditions: visual, kinesthetic, and visuokinesthetic. Errors in direction (degrees) and in distance (cm) were recorded. The analysis of the total variability in responding (E) indicated that the women of the 65- to 74-yr. age group were significantly less accurate in estimating distance than were the men of the two older age groups (45 to 54 yr., 65 to 74 yr.) and less accurate than were the women of the 25- to 34-yr. age group. No significant differences in estimating distance were found among the three age groups of men. No significant differences for direction were found between men and women.