# Leader-Follower Role Allocation for Physical Collaboration in Human Dyads
## 1 Introduction  
In our day-to-day lives, we often find ourselves in situations where collaborating with other people is necessary to achieve a certain task. A social behaviour that innately occurs in group collaboration is the leader-follower dynamic, where in order to perform a collaborative task effectively, one of the partners in collaboration must assume the role of a leader whether coordination is done through verbal [1] or non-verbal communication--through physical interaction. This dynamic has been thoroughly researched from a psychological and sociological perspective as seen in [2, 3], however has yet to be addressed in the same amount from a physical or kinematic standpoint. [PERSON] et al. [4] reviewed aspects ofdevelopmental psychology, cognitive psychology, and cognitive neuroscience that contribute to understanding human collaboration. It turned out that role allocation is one of the important areas that has yet to be sufficiently researched. Since the publication of the review, more progress in the research area of physical human collaboration has been made. A study by [PERSON] et al. found that the partners were able to improve their task performance when collaborating with each other without verbal communication or even knowing that they were collaborating. Furthermore, the study presented evidence that the task performance of both partners improved to some degree, even when the partner of the subject displayed lower task performance as an individual. This was further studied in papers by [PERSON] et al. [5; 6; 7]. Similarly, a study by [PERSON] et al. [8] showed that the experiment group where participants were coupled together outperformed the control group in solo trials, meaning collaborating with a partner also improved future solo performance. However, there is no real consensus on whether coupled partners always outperform solo performance, as studies by [PERSON] et al. [9] contradict the findings from the aforementioned studies. Furthermore, a study by [PERSON] et al. [10] displayed that although task performance improved when the subjects were in collaboration, there was no improvement in task learning due to collaborating with a partner. This indicates that the task at hand and coupling dynamics are important factors in human collaboration. In [11; 12] a study on pushing or pulling on opposite ends of a crank was performed. Here they noted improved task performance during collaboration, despite the subjects reporting that their partner was a hindrance. Similarly, evidence of the existence of a haptic channel that improves the collaborative performance, either through direct contact or interactive forces over a mutually manipulated object, was reported in [13]. Their work indicated that haptic information may be the key component to solve the leader-follower role allocation problem. In [14] they even proposed that one partner is responsible for the plan and the other is responsible for executing the actions. On the other hand, in [15] researchers found that rigidly coupled pairs perform tasks based on pre-programmed motion plans, independent of their partner's behaviour, which could explain the sense of hindrance observed in [11; 12]. The existence of an unequal control in human collaboration was further observed in [16] and more recently investigated in [17]. In this study we would like to build upon the aforementioned findings on human collaboration and leader-follower role allocation by investigating whether the leader-follower dynamics, or in other words the dominance of one partner in a physical collaborative task, can be predicted through the observation of the partners' individual task performance. Based on the results of the study by [PERSON] et al.