Figure 1. Virtual reality views and experimental setup used in the experiments.

(A) Virtual tools in an uncrossed posture: the small balls on the upper and lower part of the tools are the visual distractors. They are presented simultaneously with the vibrotactile stimuli to distract the participants. They can be presented at the same positions as the vibrotactile stimuli (congruent) or at different positions (incongruent). (B) Virtual tools in a crossed posture: The big balls in the middle of the tools have two functions. First they indicate that the CCE phase is finished. Second they indicate the position to locate the tools to keep the distance between each tool constant. The big cross in the middle of the tools is the fixation point. (C, D) A cable driven haptic device (the Da Vinci Simulator) with a large workspace was used. Participants interacted with the virtual object through the handles of the device. Their interactions were shown through a head mounted display. To mask the noise of the vibrators and environmental noise, headphones were used to present white noise. Participants responded to vibrotactile stimuli using the foot pedal. A chin rest system was used to prevent undesired movement of the head. The participant has given written informed consent (according to the PLoS guidelines) for the publication of her picture.