# Movement Time and Subjective Rating of Difficulty in Real and Virtual Pipe Transferring Tasks
## 4 Discussion  
### Virtual and Real Pipe Transfers  
The MT of transferring a real pipe was significantly (\(p<0.0001\)) longer than that of transferring a virtual pipe for both lateral and anterior-posterior transferring. Our first hypothesis was rejected. The lack of efficiency in pointing virtual targets which occurred in [PERSON] et al. [5] did not occur in our pipe transferring tasks. This may be attributed to the fact that the movements of our pipe transferring were much more complicated than that of pointing a target. The participants in [PERSON] et al. [5] needed only to move their fingertips to tap the button on a keypad, while our participants needed to grasp or pinch the pipe, transfer it to the end, and then release the pipe. For real pipe transferring, the participants pinched the \(\omega 2.2\) cm pipe and grasped the pipes of the other two dimensions to hold the pipe firmly. For virtual pipes, the \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline
**Transfer Direction** & **Pipe** & **Diameter** & \(\beta_{1}\) & \(\beta_{2}\) & \(\beta_{3}\) & \(1/\beta_{3}\) & \(\text{R}_{\text{adj}}\)2 \\ \hline Lateral & Real & \(2.2\) & \(-314.6\) & \(131.5\)\({}^{\dagger}\) & \(465.5\) & \(2.1\) & \(0.91\) \\  & & \(4.7\) & \(-204.2\) & \(190.1\)\({}^{\dagger\dagger}\) & \(506.6\) & \(2.0\) & \(0.91\) \\  & & \(6.0\) & \(-316.2\) & \(-\)\({}^{\ast}\) & \(580.3\) & \(1.7\) & \(0.92\) \\  & Virtual & \(2.2\) & \(-\)\({}^{\ast}\) & \(-\)\({}^{\ast}\) & \(291.2\) & \(3.4\) & \(0.93\) \\  & & \(4.7\) & \(-84.7\)\({}^{\dagger\dagger}\) & \(-\)\({}^{\ast}\) & \(317.7\) & \(3.1\) & \(0.95\) \\  & & \(6.0\) & \(-66.5\)\({}^{\dagger}\) & \(-\)\({}^{\ast}\) & \(306.5\) & \(3.3\) & \(0.96\) \\ \hline Anterior-posterior & Real & \(2.2\) & \(-196.5\)\({}^{\dagger\dagger}\) & \(235.9\) & \(426.2\) & \(2.3\) & \(0.91\) \\  & Virtual & \(2.2\) & \(-149.6\)\({}^{\dagger\dagger}\) & \(-\)\({}^{\ast}\) & \(319.7\) & \(3.1\) & \(0.88\) \\ \hline \hline \end{tabular} Note: all the \(\beta_{1}\), \(\beta_{2}\), and \(\beta_{3}\) were statistically significant at \(p<0.0001\) except those at \({}^{\ast}p<0.05\), \({}^{\ast\dagger}p<0.01\), and \({}^{\ast}p>0.05\). The unit for MT, \(\beta_{1}\), and \(\beta_{2}\) is ms; the unit of \(\beta_{3}\) is ms/bit. The units of diameter and \(1/\beta_{3}\) are cm and bit/s, respectively.  
\end{table} 
Table 2: Regression coefficients and \(\text{R}_{\text{adj}}\)2 of the MT models. participants could either pinch or grasp the pipe no matter how large the pipe was. The Holopipe app recognizes a catch of the pipe when the fingertip of the index finger is in touch with the thumb. We observed that most of our participants pinched the virtual pipes for all three dimensions. The virtual pipe did not \"drop\" unless the tips of the index finger and the thumb were not in contact with each other during the transfer of the pipe. Pinching was easier than grasping in both holding and releasing a pipe because the former involves only the index finger, while the latter involves all four fingers in addition to the thumb. Moreover, the participants needed to aim at the end circle before they could put the pipe in the circle. It was also easier to aim at the end circle while pinching than while grasping. These were the main reasons why transferring a virtual pipe was perceived as easier and required less time to complete than transferring a real one. Our findings should be considered when implementing an AR device in training programs involving object transferring. The efficiency in transferring virtual objects could be significantly higher than that of transferring real objects of the same dimension for the same distance. Trainees who transfer virtual objects using an AR device in a training program might overestimate the efficiency of object transferring which will occur in the real world. As we have mentioned earlier, when the hands of the participants reached the virtual pipe, a virtual cubic frame appeared.