Competition Increases the Effort Put Into a Physical Interaction Task.

Physical interaction can enhance motor learning, but it remains unclear what type of interaction is best suited to increasing the active effort put into a task, which should support learning. Here, we used the same interactive tracking task with different instructions to induce three training conditions: competition, collaboration, and self-improvement, where partners improve their own performance while interacting haptically with each other. The effort was gauged by measuring the total normalized muscle activity. Feedback of task performance and the haptic dynamics were identical in all three training conditions, so the effort needed to complete the task was the same. Only the instructions to 'compete with the partner', 'improve your and your partner's accuracy' and 'improve your accuracy' were different among the competition, collaboration, and self-improvement conditions, respectively. Despite having the same goal of maximizing self-performance during competition and self-improvement, participants exerted significantly more effort during competition, and their tracking accuracy was highest during competitive practice. Least effort was put into collaboration but tracking accuracy during collaboration was comparable to self-improvement. Our results suggest that interactive haptic competition can induce higher active drive or effort than either collaborative training or self-focused practice.

Arm movement adaptation to concurrent pain constraints.

How do humans coordinate their movements in order to avoid pain? This paper investigates a motor task in the presence of concurrent potential pain sources: the arm must be withdrawn to avoid a slap on the hand while avoiding an elbow obstacle with an electrical noxious stimulation. The results show that our subjects learned to control the hand retraction movement in order to avoid the potential pain. Subject-specific motor strategies were used to modify the joint movement coordination to avoid hitting the obstacle with the elbow at the cost of increasing the risk of hand slap. Furthermore, they used a conservative strategy as if assuming an obstacle in 100% of the trials.

Facing the partner influences exchanges in force.

Many studies in psychology have documented how the behaviour of verbally communicating pairs is affected by social factors such as the partner's gaze. However, few studies have examined whether physically interacting pairs are influenced by social factors. Here, we asked two partners to exchange forces with one another, where the goal was to accurately replicate the force back onto the other. We first measured an individual's accuracy in reproducing a force from a robot. We then tested pairs who knowingly exchanged forces whilst separated by a curtain. These separated pairs exchanged forces as two independent individuals would, hence the force reproduction accuracy of partners is not affected by knowingly reproducing a force onto a nonvisible partner. On the other hand, pairs who exchanged forces whilst facing one another consistently under-reproduced the partner's force in comparison to separated partners. Thus, the force reproduction accuracy of subjects is strongly biased by facing a partner.

Artificial nociception and motor responses to pain, for humans and robots.

This concept paper describes nociception and the role of pain in humans. Understanding the mechanisms of pain can give insight into the implementation of artificial pain for robots. Identification of noxious contacts could help robots to elicit reactions in order to avoid or minimize damage to the robot and the environment. The information processing of artificial pain can also be used to optimally regulate incoming sensory information and prevent accidents or real pain to the users of robotic systems and prostheses, improving the performance of robots and their interaction with human users. Besides the applications of artificial nociception for robotic manipulation and intelligent prostheses, the development of computational models of pain mechanisms for the discrimination of noxious stimuli from innocuous touch can find crucial clinical applications, addressing the vulnerable non-verbal population who are unable to report pain.