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.

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.

This paper presents a simple device for the investigation of the human somatosensory system with functional magnetic imaging (fMRI). PC-controlled pneumatic actuation is employed to produce innocuous or noxious mechanical stimulation of the skin. Stimulation patterns are synchronized with fMRI and other relevant physiological measurements like electroencephalographic activity and vital physiological parameters. The system allows adjustable regulation of stimulation parameters and provides consistent patterns of stimulation. A validation experiment demonstrates that the system safely and reliably identifies clusters of functional activity in brain regions involved in the processing of pain. This new device is inexpensive, portable, easy-to-assemble and customizable to suit different experimental requirements. It provides robust and consistent somatosensory stimulation, which is of crucial importance to investigating the mechanisms of pain and its strong connection with the sense of touch.

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.

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