Inclusion CriteriaPatients will be included in the study if they meet the following criteria:
1. naïve subjects who have never experienced robot-assisted therapy as inpatients or outpatients;
2. first single focal unilateral lesion with diagnosis verified by brain imaging (MRI or CT scans) that has occurred at least 6 months prior;
3. cognitive function sufficient to understand the experiments and follow instructions (Mini-Mental Status Score of 22 and higher or interview for aphasic subjects);
4. average Motor Power score >= 1/5 or <= 3/5 (neither hemiplegic nor fully recovered motor function in 6 muscles of the shoulder, elbow, and wrist);
5. informed written consent to participate in the study.