Collaborative Research: Coordination of Multi-Digit Forces During Grasping

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How does the brain work with the human body to control behavior? This question holds many deep issues that are central to the behavioral and cognitive sciences. Some of them are more philosophical in nature (like the famous mind/body problem of Cartesian dualism), while others are more mechanical. One of the most general mechanical issues with behavioral control is often referred to as the "degrees of freedom" problem. The problem is that action goals may very often be reached by many different paths of action. To illustrate, imagine the act of picking up a cup of coffee. Healthy adults take this act for granted as trivially easy, but from the perspective of the human brain and body, there is non-trivial problem to be solved. The problem is that there is a vast number of distinct trajectories of the torso, arms, and fingers that may all suffice to accomplish the task of lifting the cup. How does the system choose among the vast array of possibilities so efficiently and effortlessly?With support of the National Science Foundation, Dr. Santello and Dr. Gordon will conduct a series of experiments on human grasp behaviors to better understand the nature of behavioral control. The experiments will focus on the coordination of the fingers in response to the forces that are imposed upon them while maintaining the goal of holding an object and not allowing it to slip or tilt. Prior research suggests that grasping behaviors are governed in part by a tendency to simplify the control of the fingers, which helps to alleviate the degrees of freedom problem. However, there is also reason to believe that this tendency is itself a complex phenomenon because what is simple may depend on the particularities of the grasping task. The primary aim of this collaborative research project is to investigate the task-dependency of grasp control. Grasping serves as a simple laboratory task for more generally investigating the remarkably flexible and adaptive nature of human behavior. The knowledge to be gained in this research project may also inform the development of more dexterous robotic manipulators, as well as remotely operated machinery that is capable of handling fragile or dangerous objects.