Ecological Task Analysis (ETA; Davis & Burton, 1991) hypothesizes that movement change may emerge from dynamic interaction in given environmental conditions. In other words, task variability provides opportunities for the performer to choose skills suitable to his or her capabilities in order to achieve a task goal. Choi, Hawkins, and Langley (2007) found that children positioned the humerus above the shoulder in order to create the trajectory required when aiming at a high target in both vertical and horizontal orientations.
Purpose
This study extends that research in order to (1) examine four 4 year-old children's changes in humerus positions in response to more complex target variations; and (2) examine their perceptual judgment as reflected in changes in humerus position as correlated with success.
Methods
A single case alternating treatment design was used to evaluate the data. Eight task variations were created by adjusting the height of the target as well as its slope, including 45 degree angles tilted toward and away from the throwers, in addition to vertical and horizontal orientations. Therefore, this study used four orientations (vertical, horizontal, angle toward, angle away) and 2 levels (below and above eye heights) for each orientation. The targets were alternately introduced in a different order for each subject. Four children enrolled in KinderSkills, a movement program at a large state university, participated in this study. Data were collected once a week for a seven-week period and all sessions were videotaped. Inter-observer agreement was assessed.
Analysis/Results
Results were that subjects changed their humerus positions as a different task condition was introduced. Two-thirds of the time, subjects changed patterns based on a target orientation change; an even greater proportion of changes based on orientation took place for the most stable and mature performers, who scored most and used the most consistent throwing patterns. This study confirmed that the lower humerus position was used many more times for low targets than for high targets, and that the high humerus position was used many more times for high targets. It also discovered that the high humerus position was used more for high difficulty targets, and the elbow shoulder position appears to be a transitional form used for both high and low targets.
Conclusions
We concluded that maturity is characterized by consistency in movement pattern and at the same time is responsive to contextual information in terms of task variation, at least within condition.