Opinion

Science

“What's the secret?” A creative way to "watch" as demonstrated by a seasoned kendama player

Hiroyuki Mishima
Associate Professor, Faculty of Human Sciences, Waseda University

At work or away from work, we all experience situations in which we know exactly what to do but for some reason lack in execution. It could be a sporting hobby or driving. You may sometimes ruin the food you are cooking. We can spend hours of frustration with things we cannot do well. On the other hand, however, I am sure we have all experienced a moment where we discovered the secret behind a certain activity. I think is the same with those who master riding a bike after consistent practice. Once you learn the secret, you will quickly improve, and the secret will likely stay with you.

A scientific approach to kendama techniques

We are conducting several studies in our lab, one involving driving automobiles, in order to reveal the mechanism behind "uncovering a secret." One of the studies involves kendama -a traditional Japanese game based on a French ball-and-cup game bilboquet-and is led by my colleague, Mariko Ito, Ph.D. This article will introduce some of this study’s findings.

Figure 1. Ball trajectory demonstrated by a skilled player (seen from the right side of the player). The zero coordinate is set to a spot at the player's foot.

There are over 100 kendama tricks-or thousands of tricks depending on how you count-but our study focuses on furiken (swing in), one of the ten basic techniques used in the grade promotion test. This technique consists of the following steps: (1) holding the grip of the kendama handle with the dominant hand and letting the ball naturally hang from the handle, (2) slightly pulling the ball with the other hand toward the body and pushing it forward as if pushing a swing, (3) pulling the handle towards you to pull the ball, now moving forward in the air, toward the body at the right time, and (4) catching the ball, moving back toward the body as it rises in the air, on the tip. (The Japan Kendama Association website has a video.) This is a relatively difficult technique and beginners may never succeed. To be able to catch the ball on the tip, the hole in the ball must align with the mount where the tip is. To do so, the ball must be flipped midair, which is a difficult maneuver for beginners. Skilled kendama players, however, perform this technique successfully almost 100% of the time. The hypothesis drawn from our study is that learning the secret behind this technique is the key to explaining the different rates of success.

To discover the key to skilled players successfully performing furiken, we recorded and analyzed their performance using a motion capture system that records motion in 3D coordinates. Figure 1 shows the trajectory of the ball seen from the right side of the player. Multiple trials resulted in multiple trajectory lines. In this figure, the tip catches the ball all over the place, and we are unable to find the secret of a skilled player's stable performance. One of our predictions was that the motion of the skilled player was stable and therefore the ball’s trajectory was also stable. The trial results, however, indicated that the trajectory of the ball-simply connected to the handle via a string-fluctuated to some degree even when controlled by a skilled player.

In further studies, while analyzing the players’ movements, we noticed the player’s head following the ball’s movement in a large arc. Figure 2 shows an advantageous effect of such characteristic movement by a skilled player Although the same set of data is used in Figures 1 and 2, the reference point in Figure 2 is the player's head and the curves show the relative ball position. Differing from Figure 1, Figure 2 indicates that the tip catches the ball in a very small controlled area.

So, how about kendama beginners? Figure 3 was created under the same conditions as Figure 2, but for a kendama beginner. It is clear that the place where the tip catches the ball fluctuates for the beginner when compared with the skilled player (Figure 2). This means that the beginner was unable to effectively move their head to match the movement of the moving ball.

Figure 2. Ball trajectory relative to the skilled player's head

Figure 3. Ball trajectory relative to the beginner's head

Uncovering the kendama secret

We found from the study’s results that the movement of the skilled player's head matched the movement of the ball exactly. The major benefit of this skill is that it allows the player to accurately observe the ball by canceling the speed of the fast-moving target (ball) to allow the ball to stay at the center of the visual field and be perceived as a slow-moving target. Imagine yourself on a train platform and a train passes at 80 km per hour. It is impossible to see the face of individual passengers from the platform, but it is easy to do so if you are on a train that runs in the same direction alongside the target train at the same speed. The same logic applies to both cases.

In kendama practice, players are sometimes instructed to skillfully use their knees. This instruction may sound like the secret for improving body movement in order to stabilize the lower body or push out the ball in a stable motion. Using the knees, however, requires one to move the head, located above the knees, in the same way as the ball. We believe, that this means the knees are used to strengthen perception and allow the player to better watch their target.

What's behind the secret?

It is extremely difficult even for expert kendama players to successfully perform in the dark. If they are unable to perceive the necessary information, they cannot perform successfully even if they improve their stamina, speed, and reaction time. We think secrets can be physical or perceptive. If you have difficulty improving yourself in an activity, you might want to think about whether or not you are getting enough information to achieve the target outcome and try to find a way to better "watch" the movements involved.

Reference

Japan Kendama Association website(http://kendama.or.jp/english/)

Ito, M., Mishima, H., & Sasaki, M. (2011). The Dynamical Stability of Visual Coupling and Knee Flexibility in Skilled Kendama Players, Ecological Psychology, 23(4), 308-332.

Hiroyuki Mishima
Associate Professor, Faculty of Human Sciences, Waseda University

[Profile]
Field of study: Ecological psychology
Education: Hiroyuki Mishima is a Ph.D in human sciences. At Waseda University, he completed his Ph.D. in the Graduate School of Human Sciences in 1997 after graduating from the Department of Basic Human Sciences, School of Human Sciences in 1992.
Career: Hiroyuki Mishima has been Associate Professor, Faculty of Human Sciences, Waseda University since 2007. His prior career includes: Associate Professor, Faculty of Education and Regional Studies, University of Fukui (1999); Associate Professor, Faculty of Education, University of Fukui (1998); Research Associate, Department of Basic Human Sciences, School of Human Sciences, Waseda University (1996); and Research Fellow of the Japan Society for the Promotion of Science (1994)
Publication: "Ekorojikaru Maindo: Chisei to Kankyou wo Tsunagu Shinrigaku" ["Ecological Mind: Psychology that Connects Intelligence and Environment"] (NHK Publishing, Inc.)