## 6 Results and Discussion
### Discussion
The combined disturbance increased 372% in time performance. Questionnaires showed that:  
1. users found it quite \"easy to use both visualization interfaces\", traditional and immersive (\(\mu_{t}=2.9\), \(\sigma_{t}=1.54\) vs. \(\mu_{i}=2.42\), \(\sigma_{i}=1.53\)) (the subscript \(t\) stands for traditional and \(i\) for immersive). 2. users did not consider the pick, insert, and place task (Task 2) as a \"tiring\" one using either interface (\(\mu_{t}=2.66\), \(\sigma_{t}=1.59\) vs. \(\mu_{i}=2.61\), \(\sigma_{i}=1.46\)). Q2 did not present significant differences because the question addressed a common task. 3. users felt that their \"movement action\" was more precise using the immersive interface (HMD providing an active point of view) (\(\mu_{t}=4.33\), \(\sigma_{t}=1.19\) vs. \(\mu_{i}=5.47\), \(\sigma_{i}=1.07\)). This significant difference results from the gain in depth perception, a consequence of motion parallax. Better visual depth feedback helps to calibrate the arm proprioception system, enabling finer movements of the tool. By moving and seeing our arm, or seeing the tool as an extension of our limb in an unknown 3D space, it helps us to perceive the spatial dimension and localize objects. 4. Inquiring about which interface enabled a better visualization to manipulate objects, it was clearly stated that it was the immersive interface (\(\mu_{t}=4.38\), \(\sigma_{t}=1.65\) vs. \(\mu_{i}=5.52\), \(\sigma_{i}=0.74\)). Subjective scores were statistically significant, and quantitative time mean performances measurements confirmed these results. Task 2 itself is an easy one, and in terms of usability, the preference was for the immersive interface. 5. Inquiring about if users were aware that \"visualization\" was being supported through an \"indirect technological device\", they answered that they forgot more easily when they were using the immersive interface (\(\mu_{t}=3.42\), \(\sigma_{t}=1.77\) vs. \(\mu_{i}=5.28\), \(\sigma_{i}=1.58\)). It is understandable that users answered this way, as the immersive interface provides a more natural point of view. People tend to forget that their own eyes are not really in the remote space. This is a confirmation of the importance of the view point transfer proposal as a key element for achieving telepresence. 6. Users also thought that with the immersive interface, they had \"a clear perception and total control of stick/tool movements\" (\(\mu_{t}=4.80\), \(\sigma_{t}=1.47\) vs. \(\mu_{i}=5.28\), \(\sigma_{i}=1.18\)). This result might require more samples to become statistically validated; notice, however, that some of spatial perception arises from monocular cues already available in the traditional interface (\(Fix_{Display}+Fix_{Cam}\)). Pictorial cues in a single image and movements in the scene can provide depth information. This type of cue provides information about occlusion, relative height, relative size, perspective convergence, texture gradient, and shadows, enough to perceive the space. 7. The vast majority of users were unanimous in stating that they \"they perform better when they move their\" heads (\(\mu_{t}=5.14\), \(\sigma_{t}=2.26\) vs. \(\mu_{i}=2.40\), \(\sigma_{i}=2.11\)). Although this question does not make sense with relation to the traditional interface, because a fixed monitor (\(Fix_{Display}+Fix_{Cam}\)) does not provide a dynamic point of view, it still provides monocular cues related to depth. On the other end, by moving the user's head, the immersive interface adds to the mentioned monocular cues and the motion-produced cues, like motion parallax, accretion, and deletion. Besides the benefit of depth information from motion parallax, users can play with occlusion to match their mental models. * Inquiring about the importance of the sense of touch during an interaction, users confirmed the importance of haptic feedback.