Human-like Robotic Controllers for Enhanced Motor Learning

The participants will be single-blinded and complete a tracking task as either: solo task, collaboration task (both participants work on a common task synchronously to achieve a goal; this is a summative effort to achieve the goal), competition task (each participant has to achieve a goal at the expense of his or her partner, therefore maximizing effort or error of the partner in reaching the goal), or cooperation task (an asymmetric partnership with an active partner and a passive partner working towards a goal).

The subjects will complete their task at 3 impedance levels: high (a virtual stiffness 160-200 N/m and damping 0\~10 Nm/s; this will be a stiff connection in which the subjects feel like they are connected via rigid links and each subject will perceive the other partner's movement directly), medium (a virtual stiffness 100-140 N/m and damping 0\~10 Nm/s; this will be a spring like-connection in which the subjects feel like they are connected with a spring and each subject will perceive the other partner with a force that is proportional to the trajectory difference of the two participants), and soft (a virtual stiffness 40-80 N/m and damping 0\~10 Nm/s; this will be a spring like connection in which the subjects feel like they are connected with a loose spring and each subject will perceive the other partner with a force that is proportional to the trajectory difference of the two subjects, however, this force will be smaller than that of the medium impedance).

There will be two skill levels: novice (a participant who has no prior experience with the trajectory tracking experiment; in testing with the clinical populations, the investigators will assign this condition to the clinical participant) and expert (a participant who is experienced with the trajectory tracking experiment and who can achieve a tracking error \[difference of the desired trajectory and actual trajectory\] below a certain threshold; in testing with the clinical population, the investigators will assign this condition to the therapist). Participants will start experimentation paired as novice-novice, and at the end of the session may be invited to continue additional sessions to be paired as the expert in a novice-expert dyad.

The subjects will complete 10 training sessions per assistive robot for the researchers to observe motor learning and functional outcomes.