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Motor coordination: when two have to act as one.

Braun DA, Ortega PA, Wolpert DM - Exp Brain Res (2011)

Bottom Line: In these tasks, subjects made reaching movements reflecting their continuously evolving "decisions" while they received a continuous payoff in the form of a resistive force counteracting their movements.Successful coordination required two subjects to "choose" the same Nash equilibrium in this force-payoff landscape within a single reach.Our results suggest that two-person coordination arises naturally in motor interactions and is facilitated by favorable initial positions, stereotypical motor pattern, and differences in response times.

View Article: PubMed Central - PubMed

Affiliation: Department of Engineering, Computational and Biological Learning Laboratory, University of Cambridge, Cambridge, UK. dab54@cam.ac.uk

ABSTRACT
Trying to pass someone walking toward you in a narrow corridor is a familiar example of a two-person motor game that requires coordination. In this study, we investigate coordination in sensorimotor tasks that correspond to classic coordination games with multiple Nash equilibria, such as "choosing sides," "stag hunt," "chicken," and "battle of sexes". In these tasks, subjects made reaching movements reflecting their continuously evolving "decisions" while they received a continuous payoff in the form of a resistive force counteracting their movements. Successful coordination required two subjects to "choose" the same Nash equilibrium in this force-payoff landscape within a single reach. We found that on the majority of trials coordination was achieved. Compared to the proportion of trials in which miscoordination occurred, successful coordination was characterized by several distinct features: an increased mutual information between the players' movement endpoints, an increased joint entropy during the movements, and by differences in the timing of the players' responses. Moreover, we found that the probability of successful coordination depends on the players' initial distance from the Nash equilibria. Our results suggest that two-person coordination arises naturally in motor interactions and is facilitated by favorable initial positions, stereotypical motor pattern, and differences in response times.

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Related in: MedlinePlus

Experimental setup. Player 1 and Player 2 each control a cursor from a start bar to a target bar. The movement can be chosen anywhere along the x-axes. However, the forces that resist the players’ forward movement are given by spring constants whose stiffness depend both on the x-position of Player 1 and on the x-position of Player 2
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Fig1: Experimental setup. Player 1 and Player 2 each control a cursor from a start bar to a target bar. The movement can be chosen anywhere along the x-axes. However, the forces that resist the players’ forward movement are given by spring constants whose stiffness depend both on the x-position of Player 1 and on the x-position of Player 2

Mentions: The experiment was conducted using two vBOTs which are planar robotic interfaces. The custom-built device consists of a parallelogram constructed mainly from carbon fiber tubes that are driven by rare earth motors via low-friction timing belts. High-resolution incremental encoders are attached to the drive motors to permit accurate computation of the robot’s position. Care was taken with the design to ensure it was capable of exerting large end-point forces while still exhibiting high stiffness, low friction, and also low inertia. The robot’s motors were run from a pair of switching torque control amplifiers that were interfaced, along with the encoders, to a multifunctional I/O card on a PC using some simple logic to implement safety features. Software control of the robot was achieved by means of a control loop running at 1,000 Hz, in which position and force were measured and desired output force was set. For further technical details, see (Howard et al. 2009). Participants held the handle of the vBOT that constrained hand movements to the horizontal plane. Using a projection system, we overlaid virtual visual feedback into the plane of the movement. Each of the vBOT handles controlled the position of a circular cursor (gray color, radius 1.25 cm) in one half of the workspace (Fig. 1). The position of the cursor was updated continuously throughout the trial.Fig. 1


Motor coordination: when two have to act as one.

Braun DA, Ortega PA, Wolpert DM - Exp Brain Res (2011)

Experimental setup. Player 1 and Player 2 each control a cursor from a start bar to a target bar. The movement can be chosen anywhere along the x-axes. However, the forces that resist the players’ forward movement are given by spring constants whose stiffness depend both on the x-position of Player 1 and on the x-position of Player 2
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3102209&req=5

Fig1: Experimental setup. Player 1 and Player 2 each control a cursor from a start bar to a target bar. The movement can be chosen anywhere along the x-axes. However, the forces that resist the players’ forward movement are given by spring constants whose stiffness depend both on the x-position of Player 1 and on the x-position of Player 2
Mentions: The experiment was conducted using two vBOTs which are planar robotic interfaces. The custom-built device consists of a parallelogram constructed mainly from carbon fiber tubes that are driven by rare earth motors via low-friction timing belts. High-resolution incremental encoders are attached to the drive motors to permit accurate computation of the robot’s position. Care was taken with the design to ensure it was capable of exerting large end-point forces while still exhibiting high stiffness, low friction, and also low inertia. The robot’s motors were run from a pair of switching torque control amplifiers that were interfaced, along with the encoders, to a multifunctional I/O card on a PC using some simple logic to implement safety features. Software control of the robot was achieved by means of a control loop running at 1,000 Hz, in which position and force were measured and desired output force was set. For further technical details, see (Howard et al. 2009). Participants held the handle of the vBOT that constrained hand movements to the horizontal plane. Using a projection system, we overlaid virtual visual feedback into the plane of the movement. Each of the vBOT handles controlled the position of a circular cursor (gray color, radius 1.25 cm) in one half of the workspace (Fig. 1). The position of the cursor was updated continuously throughout the trial.Fig. 1

Bottom Line: In these tasks, subjects made reaching movements reflecting their continuously evolving "decisions" while they received a continuous payoff in the form of a resistive force counteracting their movements.Successful coordination required two subjects to "choose" the same Nash equilibrium in this force-payoff landscape within a single reach.Our results suggest that two-person coordination arises naturally in motor interactions and is facilitated by favorable initial positions, stereotypical motor pattern, and differences in response times.

View Article: PubMed Central - PubMed

Affiliation: Department of Engineering, Computational and Biological Learning Laboratory, University of Cambridge, Cambridge, UK. dab54@cam.ac.uk

ABSTRACT
Trying to pass someone walking toward you in a narrow corridor is a familiar example of a two-person motor game that requires coordination. In this study, we investigate coordination in sensorimotor tasks that correspond to classic coordination games with multiple Nash equilibria, such as "choosing sides," "stag hunt," "chicken," and "battle of sexes". In these tasks, subjects made reaching movements reflecting their continuously evolving "decisions" while they received a continuous payoff in the form of a resistive force counteracting their movements. Successful coordination required two subjects to "choose" the same Nash equilibrium in this force-payoff landscape within a single reach. We found that on the majority of trials coordination was achieved. Compared to the proportion of trials in which miscoordination occurred, successful coordination was characterized by several distinct features: an increased mutual information between the players' movement endpoints, an increased joint entropy during the movements, and by differences in the timing of the players' responses. Moreover, we found that the probability of successful coordination depends on the players' initial distance from the Nash equilibria. Our results suggest that two-person coordination arises naturally in motor interactions and is facilitated by favorable initial positions, stereotypical motor pattern, and differences in response times.

Show MeSH
Related in: MedlinePlus