Error and Performance in Human Motor Control

Research Areas: 

How humans control fine-coordinated movements or why they fail to do so is still not completely understood. By investigating a wide spread systematic coordination error in golf putting, we hope to gain a better understanding of human motor-control. We developed an  measurement procedure that allows the quantification of the error. Subsequently, we investigate the role of online motor-control in producing the error. The results will promote our understanding about the effect of controlled vs. automatic movement execution on fine-coordinated task performance.


Methods and Research Questions: 

How humans control fine-coordinated movements is still not completely understood. A better understanding of human motor control, however, will contribute to improvements in various areas such as robotics or rehabilitation after injuries. As history has shown, we often learn what is right from looking at what is wrong. Thus, to learn more about coordination, we investigate a movement that is systematically flawed by a disruption of its coordination.

One such movement is the yips in golf, which is defined as an involuntary muscle contraction of a planned movement and usually resulting in an interruption of the putting movement by a rotation of the wrist prior to impact with the ball. Currently, there are no comprehensive biomechanical analysis, including kinematic, neuromuscular, and behavioral measurements of the putting yips. Such an analysis, however, could reveal factors on a functional level that are responsible for the systematic error. Moreover, such an analysis makes it possible to measure and quantify the error. The latter is especially relevant for future studies in which we wish to investigate potential influencing factors such as the role of online motor-control (e.g., visual attention and proprioceptive feedback) and the role of the ball during impact.

In phase 1 we generate a clearer picture of the yips from a biomechanical perspective and lay the necessary foundation for further investigation. To this end, we use a 12-camera VICON NEXUS system that allows the 3D motion capturing of the whole body and the golf club. The system is synchronized with a wireless EMG system that allows the additional recording of muscle activity throughout the movement. Utilizing the system, we analyze the putting movement of high-level experts and develop a reference structure with which we compare the kinematic and physiological characteristics of the systematic error. Moreover, we employ a within-subject design to distinguish error prone circumstances from circumstances with errorless movement execution. Phase 1 provides a measurement and the possibility to quantify the error, which is necessary to test the influence of other factors. In phase 2 of the project we plan to manipulate the available information sources required for online control of the movement by means of occlusion paradigms. Additionally, we plan to investigate which role the ball has in provoking the error before impact.



Currently, it seems that the typical yips can be measured by the wrist rotation before the impact with the ball. The rotation resembles an oscillation around the square impact with the ball. It seems to occur reliable in the dominant arm whenever the affected participant attempts to hit the ball. In the non-dominant hand or when there is no ball present the oscillating movement usually does not occur. Future results on the role of online motor-control and the role of the anticipated impact with ball might shed more light on (a) the effect of intentionally controlled execution (i.e., focus on the process) versus (b) the effect of rather automatic execution (i.e., focus on the goal) on the performance of fine-coordinated movements.