“…Shared control, especially when an input controller (e.g., a joystick) limits the number of input degrees of freedom (Aronson et al, 2018), can also be made easier for user's by providing assistance that alters the user's mental state. A robot arm can assist its user by maintaining more easily controllable state configurations (Javdani et al, 2015;Till et al, 2015;Vu et al, 2017;Aronson et al, 2018;Newman et al, 2018) or by optimizing which degrees of freedom the user can control at any given time (Herlant et al, 2016). This idea can be extended to supernumerary arms that provide users with an additional appendage but are difficult to control (Nakabayashi et al, 2018;Vatsal and Hoffman, 2018), teleoperating robotic arms through electromyography (Noda et al, 2013;Pham et al, 2017) or similar sensing devices (Muratore et al, 2019), or humanoid robots (Lin et al, 2019;Zhou et al, 2019).…”