On the human trainee side, we will focus on the cognitive and neural mechanisms underlying the acquisition of a variety of motor skills, by specifically aiming at understanding the way humans physically cooperate in acquiring a motor skill and how physical assistance affects motor learning. Experiments will enable us to identify determinants and dynamics of the learning process in representative motor tasks, and will provide the foundations for designing efficient schemes of assistance. On the robot trainer side, we will develop several robot agents for the acquisition of a variety of motor skills. They will be capable of generating appropriate schemes of assistance, based on the specific task needs and possibly learned from human experts. Robots will continuously adapt assistance, in terms of the observed performance and of neural and cognitive correlates of adaptation, to the specific user (e.g. patient) and his or her state. Robot trainers will be validated in the context of motor skill learning and robot-assisted rehabilitation. Robot agents that facilitate the capture of new motor skills may potentially benefit large groups of individuals, by helping professionals, e-g- surgeons, to acquire delicate motor skills; by providing older persons greater access to activities like fitness, sports, and arts, thus ultimately improving their quality of life. Furthermore, more effective training agents would also represent an innovative approach to robot therapy, which would likely increase its impact and extend its scope.