Embodiment experiment.

diff --git a/tex/4-loop.tex b/tex/4-loop.tex
index 059da76cb2639364672597c903a4ef2ec6f27e49..4625056199291cc78ffc3336f6530f6233ca10ed 100644 (file)
--- a/tex/4-loop.tex
+++ b/tex/4-loop.tex
@@ -908,6 +908,15 @@ To study the effect of the sample size and its effect on the statistical analysi
 To study the effect of the experiment design we simulated between-subjects design by selecting the first condition of participants.
 We considered the analysis of all participants with the within-subjects design as the ground truth, which gave the same result as the literature~\cite{botvinick98,kilteni12,kokkinara14}.
 
+\begin{figure}[htb]
+  \centering
+  \includegraphics[height=3.9cm]{figures/within-setup}\hfill
+  \includegraphics[height=3.9cm]{figures/within-environment}\hfill
+  \includegraphics[height=3.9cm]{figures/within-avatars}%
+  \caption[Setup of the embodiment methodology study.]{The user seated on a chair, performing leg movements, the virtual environment, and the two avatars.}
+  \label{fig:expewithin}
+\end{figure}
+
 Our results show that all the random subsets with at least \num{40} participants with the within-subjects design gave the same result as the ground truth.
 However, regardless of the number of participants the between-subject analyses do not reveal the ground truth effect.
 Based on the debrieffing with participants, our main explanation of this phenomenon is that participants needed a reference to provide a value for each question.
@@ -919,15 +928,6 @@ However, the effect size was about half the effect size of the within-subject an
 Therefore, we wonder if both designs even measured the same phenomenon.
 We are still working on this subject, in particular to provide calibration methods and metrics to balance groups for between-subjects design in embodiment studies.
 
-\begin{figure}[htb]
-  \centering
-  \includegraphics[height=3.9cm]{figures/within-setup}\hfill
-  \includegraphics[height=3.9cm]{figures/within-environment}\hfill
-  \includegraphics[height=3.9cm]{figures/within-avatars}%
-  \caption[Setup of the embodiment methodology study.]{The user seated on a chair, performing leg movements, the virtual environment, and the two avatars.}
-  \label{fig:expewithin}
-\end{figure}
-
 \subsubsection{Haptics and the sense of embodiment}
 
 The study of the causes and effects of the sense of embodiment of an avatar in virtual reality is a hot topic in the Virtual Reality community.
@@ -935,7 +935,7 @@ The study of the causes and effects of the sense of embodiment of an avatar in v
 Interestingly, all the embodiment questionnaires such as those we discussed before have subcomponents related to the sensorimotor loop.
 It means that the sensorimotor loop is essential ot the sense of embodiment.
 For example, people have a stronger sense of ownership when they perform actions with a visually realistic hand, and a stronger sense of agency when they embody an abstract-looking virtual hand~\cite{argelaguet16}.
-Following this idea, we studied the effect on haptics on the sense of embodiment~\cite{richard20}.
+Following this idea, we studied the effect on haptics on the sense of embodiment.
 
 We performed a user study to compare embodiment for a drawing task with force feedback, tactile feedback, and a control condition with no haptic feedback~\cite{richard20}.
 The participants were seated on a chair, and they had to paint a mandala in an immersive virtual environment with a Phantom Desktop\footnote{Today called Touch X by 3D Systems \url{https://www.3dsystems.com/haptics-devices/touch-x}} device (\reffig{fig:expeembodiment}).
@@ -945,13 +945,6 @@ We attached an EAI C2 tactor to vibrate the Phantom stylus (\reffig{fig:expeembo
 In the control condition the Phantom was only used as an input device, with no force or vibration.
 We mesured embodiment with Gonzalez Franco and Peck's first standardized questionnaire\footnote{The second one was not published at the time.} with the \emph{agency}, \emph{self location}, \emph{ownership}, and \emph{tactile sensations} subcomponents~\cite{gonzalezfranco18}.
 
-We observed a stronger embodiment in the force feedback condition compared to the control condition.
-In particular participants had a higher sense of ownership.
-However, we did not observe these differences between the tactile and control conditions.
-
-…
-task favored force feedback over tactile
-
 \begin{figure}[htb]
   \centering
   \includegraphics[height=3cm]{figures/embodimentdevice}\hfill
@@ -961,6 +954,21 @@ task favored force feedback over tactile
   \label{fig:expeembodiment}
 \end{figure}
 
+We observed a stronger embodiment in the force feedback condition compared to the control condition.
+In particular participants had a higher sense of ownership.
+However, we did not observe these differences between the tactile and control conditions.
+Besides the detailed discussion in the paper, it is important to note that in some ways this task favored the force feedback condition over the tactile condition.
+Participants certainly expected to feel the stiffness of hard surfaces.
+However, the vibrotactile feedback was symbolic because participants only received tactile guidance.
+It does not necessarily mean that the sense of embodiment requires realistic haptic feedback.
+It is not the case for visual feedback~\cite{argelaguet16}.
+But in our task force feedback constrains the stylus tip movement to prevent it from getting through the surface.
+I believe it favored sensorimotor integration, therefore participants focused on the painting task rather than controlling the stylus to paint the canvas.
+The workload analysis discussed in the paper gives supports this explanation.
+%It gave users immediate feedback that could guide them to stay close to the spatial location of the surface.
+Further studies should investigate other tasks or a variation of this one in which tactile feedback favors sensorimotor integration.
+% is expected, like feeling surface textures.
+
 \subsection{Discussion}
 
 \section{Conclusion}