\subsection{Grasp Task}
\label{grasp}

\subsubsection{Completion Time}
\label{grasp_tct}

On the time to complete a trial, there was one statistically significant effect %
of Target (\anova{7}{2868}{37.2}, \pinf{0.001}) %
but not of Hand (\anova{5}{2868}{1.8}, \p{0.1}, see \figref{results/Grasp-CompletionTime-Hand-Overall-Means}).
%
Targets on the back and the left (N, NW, and W) were slower than targets on the front (SW, S, and SE, \p{0.003}) {except for} NE (back-right) which was also fast.


\subsubsection{Contacts}
\label{grasp_contacts_count}

On the number of contacts, there were two statistically significant effects: %
Hand (\anova{5}{2868}{5.2}, \pinf{0.001}, see \figref{results/Grasp-ContactsCount-Hand-Overall-Means}) %
and Target (\anova{7}{2868}{21.2}, \pinf{0.001}).
%
Less contacts were made with Tips than with None (\qty{-13}{\%}, \p{0.02}) and Occlusion (\qty{-15}{\%}, \p{0.004});
%
and less with Mesh than with None (\qty{-15}{\%}, \p{0.006}) and Occlusion (\qty{-17}{\%}, \p{0.001}).
%
This result suggests that having no visible visual hand increased the number of failed grasps or cube drops.
%
But, surprisingly, only Tips and Mesh were statistically significantly better, not Contour nor Skeleton.
%
Targets on the back and left were more difficult (N, NW, and W) than targets on the front (SW, S, and SE, \pinf{0.001}).


\subsubsection{Time per Contact}
\label{grasp_time_per_contact}

On the mean time spent on each contact, there were two statistically significant effects: %
Hand (\anova{5}{2868}{9.6}, \pinf{0.001}, see \figref{results/Grasp-MeanContactTime-Hand-Overall-Means}) %
and Target (\anova{7}{2868}{5.6}, \pinf{0.001}).
%
It was shorter with None than with Tips (\qty{-15}{\%}, \pinf{0.001}), Skeleton (\qty{-11}{\%}, \p{0.001}) and Mesh (\qty{-11}{\%}, \p{0.001});
%
shorter with Occlusion than with Tips (\qty{-10}{\%}, \pinf{0.001}), Skeleton (\qty{-8}{\%}, \p{0.05}), and Mesh (\qty{-8}{\%}, \p{0.04});
%
shorter with Contour than with Tips (\qty{-8}{\%}, \pinf{0.001}).
%
As for the Push task, the lack of visual hand increased the number of failed grasps or cube drops.
%
The Tips rendering seemed to provide one of the best feedback for the grasping, maybe thanks to the fact that it provides information about both position and rotation of the tracked fingertips.
%
This time was the shortest on the front S than on the other target volumes (\pinf{0.001}).


\subsubsection{Grip Aperture}
\label{grasp_grip_aperture}

On the average distance between the thumb's fingertip and the other fingertips during grasping, there were two
statistically significant effects: %
Hand (\anova{5}{2868}{35.8}, \pinf{0.001}, see \figref{results/Grasp-GripAperture-Hand-Overall-Means}) %
and Target (\anova{7}{2868}{3.7}, \pinf{0.001}).
%
It was shorter with None than with Occlusion (\pinf{0.001}), Tips (\pinf{0.001}), Contour (\pinf{0.001}), Skeleton (\pinf{0.001}) and Mesh (\pinf{0.001});
%
shorter with Tips than with Occlusion (\p{0.008}), Contour (\p{0.006}) and Mesh (\pinf{0.001});
%
and shorter with Skeleton than with Mesh (\pinf{0.001}).
%
This result is an evidence of the lack of confidence of participants with no visual hand rendering: they grasped the cube more to secure it.
%
The Mesh rendering seemed to have provided the most confidence to participants, maybe because it was the closest to the real hand.
%
The Grip Aperture was longer on SE (bottom-right) target volume, indicating a higher confidence, than on back and side targets (E, NE, N, W, \p{0.03}).
