The limits of aerial and contact techniques for producing twist in reverse 1½ somersault dives

An angle-driven computer simulation model of aerial movement was used to determine the maximum amount of twist that can be produced in a reverse 1½ somersault dive from a three-metre springboard using various aerial and contact twisting techniques. The segmental inertia parameters of an elite springboard diver were used in the simulations and lower bounds were placed on the durations of arm and hip angle changes based on recorded performances of twisting somersaults. A limiting dive was identified as that producing the largest possible odd number of half twists. Simulations of the limiting dives were found using simulated annealing optimisation to produce the required amounts of somersault, tilt and twist after a flight time of 1.5 s. Additional optimisations were then run to seek solutions with the arms less adducted during the twisting phase. It was found that the upper limits ranged from 3½ to 5½ twists with arm abduction ranges lying between 8° and 23°. Similar results were obtained when the inertia parameters of two other springboard divers were used. It may be concluded that a reverse 1½ somersault dive using aerial asymmetrical arm and hip movements to produce 5½ twists is a realistic possibility. To accomplish this limiting dive the diver needs to be able to coordinate the timing of configurational changes with the progress of the twist with a precision of 10 ms or better.     

Orientation versus motion visual cues to control sensorimotor skills in some acrobatic leaps

Eight healthy male sportsmen, trained to compete at national level, were asked to perform three types of acrobatic leaps on the trampoline: twisting from stand to stand, backward somersault, and full backward twisting, with three different visual conditions: darkness, stroboscopic lighting (12 flashes per second), and normal lighting. Performances were assessed using the standardized marking system of the international gymnastic federation. All the acrobatic figures were carried out without any error in the normal lighting. However, imbalance on landing was often observed in stroboscopic lighting or in darkness, making the standard deviation significantly higher than in normal conditions. In the case of backward somersault, results were significantly better in strobe lighting than in darkness. Backward somersault was also the only case where the rotation of the body was significantly underestimated in darkness (backward imbalance). We conclude that visual cues are very important in all cases. Visual motion cues mainly seem to control the imbalance on landing, whereas visual orientation cues (the only ones to be available in strobe lighting) are used in the backward somersault to estimate the orientation of the body. In the case of a more complex leap (full backward twisting), visual orientation cues are less easily used, and probably replaced by vestibular equivalent cues.     

Use of electronic games by young children and fundamental movement skills?

This study investigated associations between pre-school children's time spent playing electronic games and their fundamental movement skills. In 2009, 53 children had physical activity (Actigraph accelerometer counts per minute), parent proxy-report of child's time in interactive and non-interactive electronic games (min./week), and movement skill (Test of Gross Motor Development-2) assessed. Hierarchical linear regression, adjusting for age (range = 3-6 years), sex (Step 1), and physical activity (cpm; M=687, SD=175.42; Step 2), examined the relationship between time in (a) non-interactive and (b) interactive electronic games and locomotor and object control skill. More than half (59%, n=31) of the children were female. Adjusted time in interactive game use was associated with object control but not locomotor skill. Adjusted time in non-interactive game use had no association with object control or locomotor skill. Greater time spent playing interactive electronic games is associated with higher object control skill proficiency in these young children. Longitudinal and experimental research is required to determine if playing these games improves object control skills or if children with greater object control skill proficiency prefer and play these games.     

Mechanical invariants are implicated in dynamic touch as a function of their salience in the stimulus flow

The authors investigated the mechanical basis of length perception through dynamic touch using specially designed rods in which the various moments of mass distribution (mass, static moment, and rotational inertia) were varied independently. In a series of 4 experiments, exploration style and rod orientation were manipulated such that the relative salience of moments of mass distribution varied markedly. Results showed that perceived length was based on the most salient moments. The authors concluded that the notion of salience is crucial for understanding the implication of moments of mass distribution in length perception and that it should play a pivotal role in developing an encompassing theory of dynamic touch.     

Gravity constraints in infant motor development

The effect of gravity in determining if and when during infancy movements eventuate and the rate at which they develop is unknown. In accordance with intersegmental relationships (Hof, 1992), a muscle moment during infancy would have to develop more rapidly than the gravitational moment before movement could occur. In this investigation, the effect of growth through the influence of gravity on the joint moments in the axial region when infants were in a prone or supine posture was examined. A mathematical model that considers the body to be composed of transverse elliptical cylinders, 1 cm deep and of known density, was used in estimating the mass of the 16 segments of the body. The gravitational moments about 3 joints within the axial region (C7-T1, T12-L1, and the hip) were determined by summation, using the radii from the joint transverse axis to the center of mass of the segments. Infants (N = 27) aged between 9 and 36 weeks at the beginning of the study were tested monthly 6 times, and the effect of growth on the gravitational moments was represented by first-order polynomials. Age x Joint analysis of variance (ANOVA) of the mean slopes of the regressions for the gravitational moments revealed significant main effects for age and joint. The means increased monotonically with the number of segments and decreased as infants aged. The mean slopes of the neck and trunk joints were significantly smaller than that of the hip joint. With increasing age, the gravitational slope was significantly smaller. The changes in the gravitational moments during infancy are seen as likely control parameters effecting phase shifts in motor patterns during development.     

EVALUATING PROGRESS IN BEHAVIORAL PROGRAMS FOR CHILDREN WITH AUTISM SPECTRUM DISORDERS VIA CONTINUOUS AND DISCONTINUOUS MEASUREMENT

We evaluated the influence of two different frequencies of data collection on skill acquisition and maintenance within behavioral treatment programs for children with autism spectrum disorders. Six children were taught multiple skills in up to four different behavioral programs. Half of the skills were measured continuously (i.e., trial by trial), and the other half were measured discontinuously (i.e., first trial only). When differences were detected, quicker acquisition was typically associated with discontinuous measurement, and stronger maintenance was typically associated with continuous measurement.     

Perceiving extents of rods by wielding: haptic diagonalization and decomposition of the inertia tensor

We report two experiments on the length-perception capabilities of the hand-related haptic subsystem. On each trial, a visually occluded rod was wielded by the subject at a position intermediate between its two ends. The position was either 1/2 or 3/4 of the rod's length. On two-thirds of the trials, a weight was attached to the rod at a point either above or below its center of gravity and not coincident with the hand's position. In Experiment 1, the subject's task was to perceive the distance reachable with the portion of the rod extending beyond the position of the grasp. In the second experiment, the subject's task was to perceive the distance reachable with the entire rod if it were held at its proximal end. In Experiment 1, perceived reaching distance was a function of the moment of inertia of the amount of rod forward of the grasp about an axis through the proximal end of the rod segment. In Experiment 2, perceived reaching distance was a function of the moment of inertia of the entire rod about the given axis of rotation intermediate between the rod's ends. The results are discussed in terms of (a) the notion of smart perceptual instruments capitalizing on invariant properties of the inertia tensor and (b) how the haptic decomposition of moments of inertia follows the principle of equivalence of forces.     

Peripheral vision and back tuck somersaults.

Although vision appears to enhance performance of somersaulting skills, few studies have investigated the source (foveal or ambient) of useful visual cues that can potentially be used by gymnasts during a somersault. Therefore, the primary objectives were to investigate the possible role of peripheral vision in the control of orientation and landing balance in a back tuck somersault. 10 female gymnasts (age = 11.6 +/- 2.7 yr., competitive level = 8 +/- 1.2, training time in gymnastics = 5.9 +/- 1.6 yr.) performed back tuck somersaults under four visual conditions (full visual field, horizontal peripheral vision limited to 100 degrees, horizonal peripheral vision limited to 60 degrees, and no vision) while wearing electromagnetic sensors that allowed automatic digitizing. Analysis yielded no statistically significant difference on any of the kinematic variables among vision conditions. Despite limiting the gymnasts' available horizontal peripheral vision, joint angles, angular velocities, and timing remained very similar. There were no statistically significant differences in landing balance between the conditions of full vision, 100 degrees peripheral vision, and 60 peripheral vision. However, gymnasts were less stable at landing when vision was absent as compared to the three other vision conditions.     

STACKING THE DECK: TEACHING SOCIAL SKILLS TO RETARDED ADULTS WITH A MODIFIED TABLE GAME

This study developed and evaluated a social skills training program for institutionalized mildly or moderately retarded and dually diagnosed individuals. Social skills were conceptualized as requiring an action or reaction within six skill areas: compliments, social interactions, politeness, criticism, social confrontation, and questions/answers. The program taught social skills using a commercially available table game, Sorry, and a specially designed card deck. Each card represented one of the skill areas and was designed to train either an actor or reactor response. The program featured response specific feedback, self-monitoring, individualized reinforcers, and individualized performance criterion levels. A multiple baseline across two groups (N = 3 per group) revealed that the game contingencies increased social skills in all targeted areas. After training, the subjects displayed their newly learned skills at or above their trained levels in two different settings with novel persons present. Although untargeted, the complexity of the subjects' responses increased across conditions, since there was a steady increase in the number of words they used per response. The program appears to be a viable means of training social skills since it uses standardized training procedures, requires only one facilitator, and is in itself a social situation that may encourage interactions with peers, cooperation, competition, and politeness.     

Assume a Spherical Chicken: Analytic Constraints,Inertia Tensor Information,and Wielded Rod Length Perception

Information associated with the inertia tensor is the preeminent explanation for haptic perception of object properties, notably wielded rod length. Critics counter that tensorial-based information requires non-tensorial supplementation (mass, torque). However, those critiques omit important constraints. With relevant constraints included, the inertia tensor alone completely specifies rod length. I list constraints inherent (but tacit) in haptic rod length perception, and show that object properties associated with the inertia tensor are invariant, even with constraints removed, by involving (a) longitudinal moment equivalents for rod mass and (b) derivatives of moments with respect to varying rotation axes. Analytic outcomes show tensorial-based information is a robust basis for wielded rod length perception, and suggest open questions for empirical exploration.     

Corrigendum to “From Poisson shot noise to the integrated Ornstein-Uhlenbeck process: Neurally principled models of information accumulation in decision-making and response time” [J. Math. Psychol. 54 (2010) 266-283]

The Corrigendum reports an error in the derivation by Smith (2010) of the moment generating function for a random-amplitude, time-inhomogeneous, Poisson shot noise process. The correct derivation of the moment generating function is given, together with corrected expressions for the moments.     

Modelling the parallel bars in men's artistic gymnastics

The modelling of the parallel bars-gymnast system is considered. A 2D frontal plane model for the parallel bars apparatus is developed, enabling technique and injury analysis to be undertaken when combined with an interacting gymnast body model. We also demonstrate how such a gymnast body model may be combined with the parallel bars model by use of a simplifying symmetry consideration about the gymnast's sagittal plane. This symmetry consideration implies that just half the gymnast body and one of the two bars, are needed in the total model. We found that midpoint vertical parallel bars dynamics may be modelled by three parameters, using a single damped spring-mass model with linear force-displacement characteristics. Horizontally, as opposed to the vertical direction, bar endpoints accounted for a substantial part (35%) of the midpoint movement, demanding two serially connected springs for this direction. One spring represented the absolute horizontal movement of the bar endpoints, while the other spring represented the superimposed horizontal movement of bar midpoint relative to the endpoints. Both horizontal springs had the same characteristics as the vertical spring, giving a total of nine parameters for the three-spring bar model. Bar parameters were estimated by fitting the modelled bar movements to corresponding measured movements caused by a 140 kg lateral pendulum below the bar midpoint. Validation was then undertaken by comparing model-predicted bar movements to corresponding measurements using lateral pendulums of 100 kg and 60 kg, respectively. Finally, a gymnast handstand position was modelled and used to compare model-predicted and measured bar oscillations following a somersault backwards to a handstand position. The model gave convincing predictions of bar movements both for the 100 kg (1 period, RMS error of 7.0 mm) and 60 kg (1 period, RMS error of 3.7 mm) pendulums, as well as for the somersault landing (2 periods, RMS error of 8.1 mm).     

The Interface Between Core Affects and the Challenge–Skill Relationship

Different models have been developed to describe human experiences. One of these models is the core affect model, which states that the core of emotional experience is a simple state of feeling good or bad, energized or drowsy. Another model is the experience fluctuation model (EFM), which has been developed to map how emotions and other experiences fluctuate along with the relationship between challenges and skills. In this study, we first mathematically refined the EFM. Second, we tested if fluctuations in core affect could be modeled with a continuous wave-like sine function (Study 1). Third, we applied the sine function to our own experience-sampling data, which we collected via mobile phones from 55 university students, and located each challenge–skill relationship in a two-dimensional core affect space (Study 2). The results were consistent in both studies and showed that fluctuations in core affect dimensions, measured as a function of the relationship between challenges and skills, can be modeled with the sine function. The results also indicated that there is a systematic link between challenge–skill relationships and core affect: High challenge–high skill situations were connected to a very active and pleasant core affect, whereas high challenge–low skill situations were connected to a quite active but unpleasant core affect, low challenge–low skill situations to a very passive and unpleasant core affect, and low challenge–high skill situations to a quite passive and pleasant core affect. Compared to previous studies, this study presents a more fine-grained and comprehensive level of information on the relationship between core affect and challenges and skills.     

Performance Indicators in Math: Implications for Brief Experimental Analysis of Academic Performance

Brief experimental analysis (BEA) can be used to specify intervention characteristics that produce positive learning gains for individual students. A key challenge to the use of BEA for intervention planning is the identification of performance indicators (including topography of the skill, measurement characteristics, and decision criteria) that meaningfully relate to longer term success in the learning environment. This study investigates the utility of various curriculum-based assessment and measurement estimates of mathematics performance for predicting functional outcomes (i.e., retention of learned skills over time and faster learning of related content in the future). All children in grades 2–5 at the participating school participated in protocol-based computational fluency-building intervention 4 days per week for an entire school year. Specific criteria were applied each week to systematically increase intervention difficulty classwide according to a pre-established sequence of computational skill objectives. Three measurements were routinely obtained. Each week children completed a timed probe of the skill for which intervention was currently occurring and a timed probe of previously mastered skills from the sequence of computational skill objectives. Each month, all children completed a timed probe of mathematics skills representing computational skills that students were expected to master by year’s end at each grade level. At all grade levels, learning a skill that appeared early in the hierarchy or sequence of skills related positively to learning of future related and more complex computational skills. Fluency criteria were specified that predicted retention of the skill over several months.     

Teamwork makes the dream work: Testing for shared perceptions on psycho-behavioural skills between athletes,coaches and parents

Psycho-behavioural skills play a key role in optimising progression through talent development, and this study investigated to what extent athlete’s self-perceptions align with those of their coaches and parents. Firstly, we examined if levels of alignment between these three raters differ across age of the athlete. To this end, 122 athletes between 9 and 18 years old (12.17 ± 2.41 years old; 47 gymnasts, 13 cyclists and 62 badminton players) completed a psycho-behavioural questionnaire. The ANOVA’s indicated low levels of correspondence between the ratings of the athlete, the coach and the parents during childhood, while better levels of shared perceptions were found in adolescence. Secondly, we investigated to what extent coaches and parents believed their own perception of the athlete’s and the perception of the athlete’s psycho-behavioural skills were accurate. Parents appeared to be more confident in accurately perceiving the psycho-behavioural skills of the athlete than coaches. Parents and coaches also believed that older athletes would be more honest on their psycho-behavioural shortcomings than younger athletes. Altogether, these findings highlight that athletes and other stakeholders in the talent development environment should strive for better alignment in perceptions on psycho-behavioural skills during the talent development pathway. With better integrated perceptions, a more functional and efficient talent development system for the athlete targeting the psycho-behavioural skills can be created.     

Which mechanical invariants are associated with the perception of length and heaviness of a nonvisible handheld rod? Testing the inertia tensor hypothesis

It has been suggested that the inertia tensor governs many instances of haptic perception. However, the evidence is inconclusive because other candidate mechanical parameters (i.e., invariants) were not or were insufficiently controlled for in pertinent experiments. By independently varying all candidate mechanical parameters, the authors were able to test the role of the inertia tensor relative to that of other mechanical parameters. The results showed that length perception during rod wielding is not governed by the inertia tensor alone but also by the static moment. In contrast to previous reports, length perception during rod holding and heaviness perception during rod wielding were found to be unrelated to the inertia tensor and strongly related to the static moment.     

Uncovering the Best Skill Multimap by Constraining the Error Probabilities of the Gain-Loss Model

The Gain-Loss model is a probabilistic skill multimap model for assessing learning processes. In practical applications, more than one skill multimap could be plausible, while none corresponds to the true one. The article investigates whether constraining the error probabilities is a way of uncovering the best skill assignment among a number of alternatives. A simulation study shows that this approach allows the detection of the models that are closest to the correct one. An empirical application shows that it allows the detection of models that are entirely derived from plausible assumptions about the skills required for solving the problems.     

Haptically Perceiving the Length of One Rod by Means of Another

Two experiments examined perception of the extent of a target rod that is contacted and wielded by a second probe rod. The equations that define the dynamics of the probe-target system suggest a higher order moment of inertia as the relevant perceptual variable. The particular inertial term implicates parameters of both the target and probe rod. Experiment 1 manipulated the inertia of the target rod and Experiment 2 manipulated the inertia of the probe rod. In both experiments, perceived length was a function of the complex inertial term. Results were discussed in terms of haptic perception at a distance, the equivalence of inert and neural appendages, and the scaling of perceived to actual variables.     

Waveform moment analysis: An ASYST program for topographical analyses of nonnegative bounded waveforms

The moments of a nonnegative bounded waveform (e.g., bounded probability density functions or responses that can be expressed as bounded probability density functions) provide the basis for characterizing the waveform. Traditionally, only the lower-order moments (k ≤ 4) have been utilized in deriving topographical indices of these waveforms. Recent advances in waveform moment analysis, however, have made it possible to derive comprehensive and interpretable indices of complex nonnegative bounded waveforms by utilizing both lower-order and higher-order moments. Waveform moment analysis is reviewed briefly, and a flexible and efficient computer program is presented for conducting waveform moment analyses.     

Alterations in the thickness of motor cortical subregions after motor-skill learning and exercise

Behavioral manipulations such as housing in an enriched environment have been shown to increase brain weight and visual cortical thickness. The present study was designed to test whether skill learning or repetitive movements can alter the thickness of the motor cortex. One group of 6-mo-old Long-Evans female rats learned motor skills on an obstacle course that increased in difficulty over training and required balance and coordination. A second group ran voluntarily in exercise wheels attached to their home cage but had little opportunity for skill learning. The third group was handled daily but received no opportunity for learning or exercise. Each condition lasted 26–29 d. The skill-learning and exercise conditions had greater heart weight, and the exercise condition had greater adrenal gland weights than controls. The thickness of the motor cortex was measured in four coronal planes between −2.33 mm to −0.3 mm from bregma. Regions of interest that corresponded to published maps of forelimb and hind-limb representations were analyzed together. Rats in the skill-learning condition had significantly thicker medial cortical areas in the two anterior planes (−0.8 and −0.3 mm from bregma). These regions correspond to previously mapped hind-limb representations. The exercise group had greater thickness of the medial region at −0.8 mm from bregma. Cortical thickness in all conditions varied significantly along the medial to lateral axis. For both treatments, the effects were restricted to medial and anterior regions of interest rather than posterior or lateral regions of interest. The results indicate that robust exercise, in addition to skill learning, is capable of altering the thickness of the motor cortex, but that the effects are restricted rather than distributed within the regions studied.