Path Model Estimates Corresponding to Figure 8.

<p>n = 40, Chi-squared goodness of fit  = 12.48, d.f.  = 9, P = 0.19.</p

The Head-Mounted Display and Tracking.

<p>(A) Participants experienced the virtual environment through a stereo wide field-of-view Head Mounted Display. (B) Upper limbs were tracked by 12 Optitrack markers grouped in 4 trackable objects. The right and left forearms were tracked for all participants. For right handed people, the right hand and the left index finger were also tracked. For left handed people, the positions of the markers were swapped and thus the right finger and the left hand were tracked.</p

Means and Standard Errors of the Angular drifts for the elongation conditions.

<p><i>AngleBefore</i> is the mean of 10 estimations of hand position at the start of the experiment. <i>AngleAfter</i> is the single estimation of hand position after the arm elongation period. <i>AngleAfter</i> is significantly greater than <i>AngleBefore</i> for <i>C2</i> (P = 0.04) and <i>C3</i> (P = 0.01) but not for <i>C4</i> (P = 0.17), Wilcoxon matched-pairs signed-rank tests.</p

Means and Standard Errors of the Hand Tracking Dispersions (meters) under the 4 elongation conditions.

<p>P is the two-tailed significance level for the Wilcoxon matched pairs sign-rank test.</p

Comparison of Questionnaire Responses of the Congruent (<i>C1</i>) and Incongruent Conditions (<i>I</i>) with Virtual Arm Length Equal to Real Arm Length.

<p>P is the significance level for equal medians using a two-tailed Mann-Whitney U Test.</p

Spatial configuration of the physical and virtual scene.

<p>(A) There were two physical boxes, the Stimulus Box shown on the right and Angle Box shown on the left. For left handed people the positions of the boxes were swapped. (B) A plastic ring was attached on top of the Angle Box. The participant was asked to put his or her dominant hand on the Stimulus Box and the other one on the Angle Box with the elbow in the plastic ring. (C) There were virtual replicas of the physical boxes. (D) In all Congruent conditions, the virtual dominant hand of the participant was seen to touch the virtual Stimulus Box corresponding to the real hand touching the real Stimulus Box. In these conditions, when the participant moved the hand over the surface of the Stimulus Box feeling its material, the same movement was made and the same tactile feedback was seen. (E) In the Incongruent condition, the virtual Stimulus Box was placed 4 meters frontwards. (F) Therefore, although the virtual movement was the same as the physical, the virtual hand was never seen to touch the virtual replica of the Stimulus Box.</p

The elongation of the virtual arm and the threat event to the virtual hand.

<p>(A) At the start of the experiment, both virtual arms were of the same size as the participant’s arms. In <i>C1</i> the virtual arm did not change length during the experiment. (B) The arm elongated to double the true length (<i>C2</i>) (C) The arm elongated to triple the true length (<i>C3</i>) (D) The arm elongated to four times the true length (<i>C4</i>). When the elongation was complete for the condition and after the last angular estimation was made, a virtual saw fell to cut the virtual arm. The participants had been instructed to stay motionless just before this. (E) The position of the virtual threat was also close to the physical body and the real hand in the no elongation condition <i>C1</i> (F) The threat was far from the real body and real hand in condition <i>C4</i>.</p

The Experiment Conditions.

<p>n = 10 for each condition in a between-groups design. Congruent visuo-tactile correlation refers to the virtual arm being in contact with the Stimulus Box while the participant was touching it, and Incongruent refers to the virtual arm not reaching the Stimulus Box. In each condition there was visuo-motor synchrony between the real and virtual dominant arm.</p

Robust Regression for <i>E</i>(log <i>L_s</i>) = <i>β</i>₀ + <i>β</i>₁<i>elongation</i> + <i>β</i>₂ log <i>L_c</i> + <i>β</i>₃<i>elongation</i> log <i>L_c</i>

<p>This uses the robustfit function of MATLAB R2009a.</p

Means and Standard Errors of S (meters) for the Incongruent and Congruent Condition with Virtual Arm Length Equal to Real Arm Length.

<p>Ps-r is the two-tailed significance level for the Wilcoxon matched pairs sign-rank test.</p><p>Pr-s is the two-tailed significance level for the Wilcoxon rank-sum test. n = 10 participants in each cell, and n = 20 in the two combined cells.</p