\input{figures/cargame.tex}
-Initially, I performed a quantitative evaluation to compare the lap times between the tactile feedback and no tactile feedback conditions.
-The results did not show any statistical significant difference.
-In hindsight, the tactile feedback could be useful to tell the players how their gestures are intepreted.
-As we will discuss later, this is an essential aspect of direct manipulation.
-However, it does not necessarily guarantee quantitative benefits.
-This was the same issue than with the dwell buttons.
-Rather than rethinking both the inputs and outputs, my understanding at the time was that I was not measuring the right thing.
-The users feedback of this first experiment suggested that the tactile sensations provided benefits in terms of realism and immersion in the game.
-Therefore I conducted the following experiment, which focused on qualitative benefits.
+\newcommand{\NoTactile}{\textsc{NT}\xspace}
+\newcommand{\Tactile}{\textsc{T}\xspace}
+
+In a first pilot study we compared performance between the tactile feedback and no tactile feedback conditions.
+In hindsight there was little chances haptic sensations increased such metrics.
+However, participants reported that the tactile sensations provided them benefits in terms of realism and immersion in the game.
+Therefore we conducted the following experiment, which focused on qualitative benefits.
+%Initially, I performed a quantitative evaluation to compare the lap times between the tactile feedback and no tactile feedback conditions.
+%The results did not show any statistical significant difference.
+%In hindsight, the tactile feedback could be useful to tell the players how their gestures are intepreted.
+%As we will discuss later, this is an essential aspect of direct manipulation.
+%However, it does not necessarily guarantee quantitative benefits.
+%This was the same issue than with the dwell buttons.
+%Rather than rethinking both the inputs and outputs, my understanding at the time was that I was not measuring the right thing.
+% The users feedback of this first experiment suggested that the tactile sensations provided benefits in terms of realism and immersion in the game.
+% Therefore I conducted the following experiment, which focused on qualitative benefits.
%In the next submission we performed a new user study and measured emotions with the PAD questionnaire (Pleasure Arousal Dominance)~\cite{mehrabian96} and presence with Witmer \etal PQ questionnaire \cite{witmer98}.
%\paragraph{Hypotheses}
We made the hypotheses that $H_1$ tactile feedback would increase the sensation of realism of the game because of the increased sensory stimulation; and $H_2$ tactile feedback would increase the users' sensation of control, because it provides them feedback about the way the game interpret their actions.
They stood \SI{2.5}{\meter} away from the Kinect during the game.
%Before the experiment the height of the Kinect was calibrated to make sure the participants' arms were in the sensor’s range.
The game was displayed on a 17” laptop screen, with a $1600 \times 900$ resolution and the same sound volume was used for all subjects.
-We opted for a between subject design: half of the participants received tactile feedback ($T$), and the other half did not ($NT$).
-We explained the mapping of the tactile feedback to the participants of condition $T$.
-Tactile feedback was not mentioned to the participants of condition $WT$.
+We opted for a between subject design: half of the participants received tactile feedback (\Tactile), and the other half did not (\NoTactile).
+We explained the mapping of the tactile feedback to the participants of condition \Tactile.
+Tactile feedback was not mentioned to the participants of condition \NoTactile.
Before they performed the task, the participants filled the immersion tendency questionnaire (ITQ)~\cite{witmer98}.
It measures the ability to get involved and focused in tasks, playing habits and the tendency to get immersed in games.
%This questionnaire identifies three factors among these items: Involvement (ability/habits to get involved in tasks), Focus (ability to stay focused on a task) and Games (playing habits and tendency to be immersed in games).
-After the experiment we measured the user’s emotional state with the Pleasure Arousal Dominance questionnaire (PAD)~\cite{mehrabian96}.
+%After the experiment we measured the user’s emotional state with the Pleasure Arousal Dominance questionnaire (PAD)~\cite{mehrabian96}.
%, which uses 7 points bipolar scales.
-We also measured spatial presence with the presence questionnaire (PQ)~[32].
+%We also measured spatial presence with the presence questionnaire (PQ)~[32].
+After the experiment we measured spatial presence with the presence questionnaire (PQ)~[32].
It measures the sensation of control, perception of sensations, distraction from the task, and realism.
%This questionnaire identifies four factors among these items: Control (sensation that user’s actions have conse-quences on the virtual environment), Sensory (how much/well the user’s senses are stimulated), Distraction (how easy the user was concentrated on the task) and Real-ism (how realistic was the simulation).
We added three additional questions about tactile feedback adapted from questions about audio feedback: 1) How much did the tactile aspects of the environment involve you? 2) How well could you identify the vibrations? 3) How well could you localize vibrations?
We analyzed our results with T-tests, Pearson correlation and Cronbach’s alpha.
\paragraph{Results}
+\reffig{fig:carpresence} shows the results of the ITQ and PQ questionnaires.
The reliability of the ITQ questionaire is acceptable (\cralpha{0.75}).
-Participants had a mean immersion tendency of $116.05/189$ in the $T$ condition, and $117.5/189$ in the $NT$ condition.
+Participants had a mean immersion tendency of $116.05/189$ in the \Tactile condition, and $117.5/189$ in the \NoTactile condition.
We did not detect any significant effect (\pEq{0.72}).
-The PQ questionnaire has a good reliability in both $T$ (\cralpha{0.89}) and $NT$ (\cralpha{0.88}) conditions.
+The PQ questionnaire had a good reliability in both \Tactile (\cralpha{0.89}) and \NoTactile (\cralpha{0.88}) conditions.
+Participants in the \Tactile condition had a $159.75/245$ mean overall Presence score whereas participants in \NoTactile condition have $142.5/245$.
+We detected a significant difference between the two conditions (\p{0.001}).
+The analysis shows a significant difference between \emph{Sensory} (\p{0.001}) and \emph{Realism} (\p{0.001}) factors.
+However, we do not detect difference in \emph{Control} (\pEq{0.55}) and \emph{Distraction} (\pEq{0.90}).
+%Moreover there is a strong positive correlation between haptic and realism items for participants in T condition (r=0.54).
-Users in T condition have a 159.75/245 mean Presence score whereas users in WT condition have 142.5/245 (Fig-ure 12, left). We detected a significant difference between the two conditions (p<0.001). The analysis of the factors identified in [32] shows that there is a significant difference between sensory (p<0.001) and realism (p<0.001, Figure 12, center) factors. However we do not detect difference in control (p=0.55) and distraction (p=0.90). Moreover there is a strong positive correlation between haptic and realism items for users in T condition (r=0.54). We computed pleasure, arousal and dominance scores by adding the score of their items and mapping the result between -1 and 1. The mean pleasure score is 0.4 in the T condition and 0.36 in the WT condition. We do not detect a significant effect (p=0.76). The mean arousal score is 0.34 in the T condi-tion and 0.46 in the WT condition, with no significant difference detected (p=0.27). The dominance score was 0.32 in the T condition and 0.15 in the WT condition (Figure 12, right). We did not detect a significant difference (p=0.07, IC=[-0.01, 0.35]).
-
-Figure 12: Presence, realism and dominance in T and WT conditions.
+% We computed pleasure, arousal and dominance scores by adding the score of their items and mapping the result between -1 and 1.
+% The mean pleasure score is 0.4 in the T condition and 0.36 in the WT condition.
+% We do not detect a significant effect (p=0.76).
+% The mean arousal score is 0.34 in the T condition and 0.46 in the WT condition, with no significant difference detected (p=0.27).
+% The dominance score was 0.32 in the T condition and 0.15 in the WT condition (Figure 12, right).
+% We did not detect a significant difference (p=0.07, IC=[-0.01, 0.35]).
+
+\begin{figure}[htb]
+ %\includegraphics[height=4cm]{figures/car-presence.pdf}
+ \includegraphics{figures/car-itq.pdf}
+ \hfill
+ \includegraphics{figures/car-presence.pdf}
+ \caption[ITQ and QT questionnaires results.]{Results of the ITQ and PQ questionnaires}
+ \label{fig:carpresence}
+\end{figure}
\paragraph{Discussion}
-We analyze the results with respect to hypotheses we made, and discuss the relationships between the design of our mappings and the results. We also discuss interesting points that emerged from discussions with the users.
-Realism
-Our first hypothesis was that tactile feedback would en-hance the realism of the game. The results shown that real-ism items of the presence questionnaire obtained better scores in the tactile condition than in the condition without tactile feedback. Moreover we found a correlation between the haptic items and the realism items for users in the T condition, which suggests a positive impact of the tactile feedback on the realism. Therefore we found support for our first hypothesis.
-The discussions we had with the users after the experiment help us to understand the explanations of this effect. Five users of the WT condition explicitly reported they did not have an impression of speed. Users in the T condition had a tactile feedback for speed. We observed users “singing” along the vibrations at high speed, and several users report-ed that tactile feedback helped them to feel the speed. These observations are not sufficient to draw a reliable assess-ment, however it gives credit to remarks made in previous research on presence in virtual environments: “The more completely and coherently all the senses are stimulated, the greater should be the capability for experiencing presence” [12], “The greater the extent of sensory information trans-mitted to appropriate sensors of the observer, the stronger the sense of presence will be” [29].
+First of all, the absence of detected difference in \emph{Immersion Tendency} between the \Tactile and \NoTactile conditions with a high p-value and small difference of means tends to indicate that there should not be a strong bias between the participant groups.
+However, this is not a definitive argument, and the problem of splitting participants into homogeneous groups is still an open question and we are currently working on it.
+
+Regarding our research question, we first hypothesized that tactile feedback would enhance the realism of the game.
+The results of the \emph{Realism} items of the \emph{Presence Questionnaire} support this hypothesis.
+In addition to this, five participants of the \NoTactile condition explicitly reported they did not have a sensation of speed while several participants of the \Tactile condition spontaneously mentioned feeling speed.
+
Control
Our second hypothesis was that the tactile feedback would enhance the user’s sensation of control. The results did not show significant effects on control items of the presence questionnaire, or dominance PAD questionnaire. However the dominance scores have a wide variance in the T condi-tion, which suggest that small effect may be detected with more users. Nevertheless we did not find support for our second hypothesis.
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