## 4 Results
### Questionnaires  
Results from the NASA TLX survey for the 12 unimpaired subjects (Figure 8(a)) can be summarized as follows: mental effort (median: 12, range: 3-17), physical fatigue (median: 6.5, range: 1-12), temporal demand (median: 10, range: 1-14), effort (median: 13, range: 2-16), frustration (median: 10, range: 4-13), and performance (median: 15.5, range: 7-20). In Figure 8(b) is visualized a comparison between the median values for each questions of the unimpaired subjects and the answers given by the two SCI participants, identified as before by the red and green color, respectively. From SUS, a usability score of 53.8636 out of 100 is obtained (STD: 16.0999, min: 25, max: 75). In Figure 9(a) are reported the maximum, minimum, and median values for each question of the questionnaire, considering all the 12 unimpaired subjects. In Figure 9(b), the median values of the unimpaired subjects are visualized together with the answers of the two individuals with spinal cord injuries. Figure 8: Success rates of target touches before (gray) and after (blue) training for **Test 1** (**a**) and **Test 2** (**b**), calculated based on the 12 unimpaired subjects. For **Test 1**, the success rate for the first target is always 100%, for the second it is 41.67% pre-training and 100% post-training, and for the third it is 16.67% pre-training and 75% post-training. For **Test 2**, the success rate improves from 41.67% pre-training to 83.33% post-training. NARS questionnaires results, divided into the three sub-scales, are the following:  
* Sub-scale S1: Attitude toward interactions with robots has a median value of 1 (mean: 1.3333, STD: 0.5164). * Sub-scale S2: Attitude toward social influence of robots has a median value of 2 (mean: 2.2, STD: 0.4472). * Sub-scale S3: Attitude toward emotional aspects in robot interaction has a median of 3 (mean: 2.6667, STD: 1.5275). Results from NASA TLX and SUS questionnaires provide important insights into the cognitive and physical demands of the system. Since NASA TLX survey reveals a high level of mental effort (median: 12) and effort (median: 13), with moderate levels of physical fatigue (median: 6.5) and temporal demand (median: 10), it can be said that the system requires a significant cognitive engagement, while the physical strain remains relatively manageable for most participants. Notably, frustration levels are moderate (median: 10) and this may be due to initial challenges in controlling the robot, as indicated by participants. The self-assessment score is very high for 11 out of 12 subjects (median: 15.5). Improvements in ease of use and efficiency are recommended. The System Usability Scale (SUS) score of 53.86 out of 100 indicates that the system's usability is below average, suggesting area for improvements. Scores in the range of 50-60 are often classified as \"marginal\", implying that the system is acceptable for some users but optimal. This finding  
Figure 10: SUS results: in (**a**) questionnaires for the 12 unimpaired subjects showing maximum, minimum, and median values for each of the questions. In (**b**), questionnaires reporting the median value of the 12 unimpaired subjects and answers of SCI 1 and SCI 2. Figure 9: NASA TLX results: in (**a**) questionnaires for the 12 unimpaired subjects showing maximum, minimum, and median values for each of the questions. In (**b**) questionnaires reporting the median value of the 12 unimpaired subjects and answers of SCI 1 and SCI 2.  
underscores the need for further refinement to enhance ease of use, reducing cognitive load and improving efficiency. Analyzing the results of the two SCI subjects (Figures 9b and 10b) and comparing them with those of unimpaired subjects (Figures 9a and 10a), both NASA TLX and SUS responses indicate a generally lower perceived workload, such as greater usability and intuitiveness of the system. This provides valuable insights for a future application of the system in the field of spinal cord injuries.