Perception of Affordances for Stepping Over an Expanse With Crutches.

Perception of possibilities for behavior reflects the task-specific fit between action capabilities and environmental properties. We investigated whether this is so for a behavior that requires spontaneously and temporarily coordinating anatomical components and inert objects into a person-plus-object action system-stepping over an expanse with crutches. We found that perception of this affordance (a) scaled to an anthropometric property of primary relevance to performing this behavior (leg length), (b) reflected the ability to perform this behavior, and that (c) variability in perception decreased with practice perceiving this affordance. The results are consistent with the proposal that perceiving affordances for a given behavior requires assembling a task-specific perceptual instrument.

Nesting in perception of affordances for stepping and leaping.

Perception of affordances for a given behavior typically reflects the task-specific action capabilities of the perceiver. However, many experiments have shown a discrepancy between the perceptual and behavioral boundaries for a given behavior. One possibility for such a discrepancy is that the context of many experimental tasks transformed what is typically a dynamic perception-action task into an analytical or reflective judgment. We investigated this hypothesis with respect to perception of maximum stepping and leaping distance. For both behaviors, perception of these affordances more closely reflected action capabilities when the perceptual task was nested within a superordinate task than when it was not (regardless of whether the behavior itself was performed). Additionally, verbal reports of perception of maximum leaping distance more closely reflected action capabilities when there was an explicit time limit on such reports. The results are discussed in the context of the ecological principle of nesting and in attentional focus during motor control tasks.

Attentional Focus Effects in Standing Long Jump Performance: Influence of a Broad and Narrow Internal Focus.

The content of instructions that strength coaches give can have a significant impact on how an athlete or client performs. Research on motor learning has shown an advantage of instructions focusing on the effects of movements (external focus) over those focusing on the movements themselves (internal focus) in the performance of motor skills. Internally focused cues are abundant in coaching, therefore the purpose of this study was to test whether some internally focused cues might be more helpful than others. Participants (68) were randomly assigned to either an external focus (EX), broad internal focus (B-IN), narrow internal focus (N-IN), or a control group (CON), and performed 5 standing long jumps. All groups were instructed that the goal was to jump as far as possible. In addition, the EX group was told to "jump as far past the start line as possible." The B-IN group was told to "use your legs." The N-IN group was told to "extend your knees as rapidly as possible," and the CON group received no additional instruction. An analysis of covariance showed that the EX group (198.09 ± 31.89 cm) jumped significantly farther than both the B-IN group (173.74 ± 35.36 cm), p = 0.010 and the N-IN group (178.53 ± 31.17 cm), p = 0.049, with no group different from the CON group. The results suggest that a broad internal focus is no more effective than a narrow internal focus, and that an external focus leads to the greatest jump distance. Strength and conditioning professionals should carefully word their instructions to induce an external focus of attention whenever possible.

Perception of maximum stepping and leaping distance: Stepping affordances as a special case of leaping affordances.

Successfully performing everyday behaviors requires perceiving affordances-possibilities for behavior that depend on the fit between environmental properties and action capabilities. Whereas affordances for some behaviors are primarily constrained by relatively static geometric properties of the perceiver (non-launching behaviors such as stepping), others are additionally constrained by dynamic force production capabilities of the perceiver (launching behaviors such as leaping). This experiment used a transfer of calibration paradigm to investigate whether visual perception of launching and non-launching behaviors represent independent perception-action tasks. In particular, we investigated whether calibration of visual perception of maximum leaping distance transferred to visual perception of maximum stepping distance, and/or vice versa. The results showed that calibration of perception of maximum leaping distance transferred to perception of maximum stepping distance, suggesting that perception of launching and non-launching are not independent. Rather, perception of stepping affordances may be a special case of perception of leaping affordances.

Relationship between socioeconomic status and physical fitness in junior high school students.

BACKGROUND: Research on physical fitness often regards socioeconomic status (SES) as a confounding factor. However, few studies investigate the impact of SES on fitness. This study investigated the impact of SES on physical fitness in both males and females, with an economic-based construct of SES. METHODS: The sample consisted of 954 6th, 7th, and 8th graders from a public, urban, Illinois middle school. The students participated in the FITNESSGRAM battery of fitness assessments as part of physical education. Descriptive statistics were calculated for height, weight, age, and sex. Students were grouped as high or low SES depending on whether they qualified for the federal free lunch program. A multivariate analysis of variance controlled for age and stratified by sex compared the raw scores from the fitness test for low and high SES students. Odds ratios stratified by sex were calculated for the likelihood of not achieving the FITNESSGRAM Healthy Fitness Zone standards among SES groups. RESULTS: Girls of the low SES group had significantly lower scores on the FITNESSGRAM assessments and were significantly less likely to achieve Healthy Fitness Zone status than the girls from the high SES groups. For boys, SES was a significant main effect for body composition but not for the other fitness tests conducted. CONCLUSION: SES is related to physical fitness in girls but not in boys. A potential explanation for this is that boys are more likely to engage in vigorous leisure time activity regardless of SES than girls.

Age, task complexity, and sex as potential moderators of attentional focus effects.

The study tested whether age, sex, or task complexity moderate the effect of attentional focus on motor learning. Children (24 boys, 24 girls) and adults (24 men, 24 women) were assigned to an internal or external attentional focus, and were timed while riding either a Double Pedalo with handles (simple task) or without handles (complex task) over a distance of 7 meters. A Double Pedalo is a four-wheeled device that involves standing on two connected platforms, and alternately pushing them forward to make it move. Participants completed 20 acquisition trials, followed by a 24-hour retention test. For the simpler task, no time differences due to attentional focus emerged. With the complex task, an external focus resulted in faster times in retention than an internal focus, but only for males. These findings suggest that attentional focus affects children and adults similarly, but task complexity and sex moderate these effects.

Alternating versus blocked practice in learning a cartwheel.

This investigation examined the generalizability of contextual interference to learning the cartwheel in gymnastics. 32 participants ages 17 to 26 years completed five stages of practice of two versions of the skill, one in which the left hand led and one in which the right hand led, providing a total of 192 practice trials. Practice of these two versions of the task was completed in either a blocked or alternating order. Tests of retention and transfer were completed 20 min. and 1 wk. after acquisition. Outcome (errors) and form scores were derived from participants' performance. Alternating practice resulted in poorer acquisition, retention, and transfer per-generalize to this task, a finding which is attributed to task complexity and the interference associated with practicing the two tasks together.

Applying contextual interference to snowboarding skills.

This investigation was designed to apply contextual interference to acquisition of snowboarding skills. 20 participants completed several acquisition stages lasting about 2 hours while either alternating the direction of the turn within each stage or completing the whole stage while attempting turns in one direction, then repeating the stage for the other direction of turn. Following acquisition, all participants returned 1 wk. later for a retention test. Alternating practice yielded better performance during acquisition and retention as measured by the arc and form attained within the turns. Because this differs from typical contextual interference effects, it is suggested that the relation between the skills may have affected the results. Negative transfer operating within blocked practice and increased between-task comparisons within alternating practice may be related to the similarity between the tasks.

Task duration in contextual interference.

Duration of practice trial on a pursuit rotor task in contextual interference was investigated. Participants practiced at each of 4 angular velocities, with 24 participants completing 28 trials lasting 20 sec., and 24 participants completing 112 trials of 5 sec. Half of the participants in each trial-duration condition practiced in a blocked format and half practiced in a random format. After random practice posttest performance was better than blocked practice when practice-trial duration was 20 sec., but worse when practice-trial duration was 5 sec. This result is not consistent with theoretical explanations of the contextual interference effect and is discussed with reference to the task characteristics and demands of the pursuit rotor.