Skill Differences in a Discrete Motor Task Emerging From the Environmental Perception Phase

Abstract

Because of the challenges associated with measuring human perception and strategy, the process of human performance from perception to motion to results is not fully understood. Therefore, this study clarifies the phase at which errors occur and how differences in skill level manifest in a motor task requiring an accurate environmental perception and fine movement control. We assigned a golf putting task and comprehensively examined various errors committed in five phases of execution. Twelve tour professionals and twelve intermediate amateur golfers performed the putting task on two surface conditions: flat and a 0.4-degree incline. The participants were instructed to describe the topographical characteristics of the green before starting the trials on each surface (environmental perception phase). Before each attempt, the participants used the reflective markers to indicate their aim point from which the ball would be launched (decision-making phase). We measured the clubface angle and impact velocity to highlight the pre-motion and motion errors (pre-motion and motion phase). In addition, mistakes in the final ball position were analyzed as result errors (post-performance phase). Our results showed that more than half of the amateurs committed visual-somatosensory errors in the perception phase. Moreover, their aiming angles in the decision-making phase differed significantly from the professionals, with no significant differences between slope conditions. In addition, alignment errors, as reported in previous studies, occurred in the pre-motion phase regardless of skill level (i.e., increased in the 0.4-degree condition). In the motion phase, the intermediate-level amateurs could not adjust their clubhead velocity control to the appropriate level, and the clubhead velocity and clubface angle control were less reproducible than those of the professionals. To understand the amateur result errors in those who misperceived the slopes, we checked the individual results focusing on the final ball position. We found that most of these participants had poor performance, especially in the 0.4-degree condition. Our results suggest that the amateurs' pre-motion and strategy errors depended on their visual-somatosensory errors.

Keywords: alignment error; decision-making; golf putting; kinematics; slope perception.

FIGURE 1

Experiment setting: (A) represents the pattern diagram of the experiment setting, while (B) shows a participant wearing shielded goggles for measurement. The experiment area where the putting platform was set was surrounded by curtains, and care was taken not to give the participants reference frames. The area surrounded by the red line indicates where participants could move freely to read the green. Two sensors were placed so that the shutter goggles would be activated when the ball passed the line 40 cm in front of where it was set. APD, anteroposterior direction; MLD, mediolateral direction.

FIGURE 2

Schematic diagram showing the definition of errors in each phase and the study measurements. The golf putting activity was divided into five phases. The error definition and measurement variables in each phase are shown.

FIGURE 3

Participants’ slope perception and average aim point in the 0- and 0.4-degree conditions. The slope perception response was divided into five patterns from (A–E). The red letters indicate answers in the 0.4-degree condition, while the blue letters indicate answers in the 0-degree condition. For example, in (A), the correct answer pattern is shown in which the left is high in the 0.4-degree condition and flat in the 0-degree condition. In (E), Ama 11 stated that the right side was high in both conditions, while Ama 2, 5, and 7 said that the left side was high in the 0-degree condition and flat in the 0.4-degree condition. Besides these slope perception responses, the participants’ aim points are shown. Both the vertical and horizontal axes for each participant show the distance (m). The coordinate (0, 0) ellipse is the ball, and the coordinate (0, 3) ellipse is the hole.

FIGURE 4

Average angles of each phase (A–C) in the 0- and 0.4-degree conditions. The angle 0 refers to the center of the target. Negative values indicate the position to the left of the target’s center, while positive values indicate the position to the right of the target’s center. *p < 0.05 and ***p < 0.001.

FIGURE 5

Average angle SDs for each phase in the 0- and 0.4-degree conditions. These values showed the intraindividual variability of face angles for each phase and were averaged for each group. *p < 0.05 and ***p < 0.001.

FIGURE 6

Average alignment error in the pre-motion phase and average motion error in the motion phase. The address-aim angle (A) indicates the average of each group of values obtained by subtracting the aim angle from the address angle. The launch-address angle (B) indicates the average of each group of values obtained by subtracting the ball launch angle from the address angle. All error bars indicate ±1SD. *p < 0.05.

FIGURE 7

Averages of impact velocity and impact velocity CV. (A) Consists of the average values of the impact velocity for each group. (B) Composed of the average values of the variation coefficient in each group. The error bars indicate ±1SD. *p < 0.05 and **p < 0.01.

FIGURE 8

Relations between the impact velocity and launch angle of all participants’ trials and hole-in trials. (A,B) The plots of all trials (240 trials) involving ball launch angle and impact velocity for the 12 people in each group. The red and blue squares show the average and SD (±1SD) of the hole-in trials in the 0.4- and 0-degree conditions, respectively. The red and blue squares in (A,B) have the same values (see also Table 3 for details regarding the hole-in trials).

FIGURE 9

Average constant errors in final ball position for each group. The circle in coordinate (0, 0) represents the target. Both the vertical and horizontal axes indicate the distance (m). The positive values on the horizontal axis mean that the FBP was to the right of the target’s center, while the negative values indicate that the FBP was to the left of the target’s center. The positive values on the vertical axis signify that the FBP was overshot from the target’s center, while the negative values on the vertical axis indicate that it was undershot. *p < 0.05.