Perception is nothing without control (of velocity)
The integration of haptic and visual perception in a virtual environment is a critical issue when there are delays between haptic and visual rendering. We suppose that integrated perception is affected of both the visual haptic discrepancies and the contact velocity of a target with an object. To test this hypothesis, we performed two experiments in which participants had to actively contact a virtual wall by using a haptic device. In the first experiment, the target velocity was held by the user (no-constant velocity task); in the second, the target velocity was kept constant at about 17mm/s (constant velocity task).We use the method of constant stimuli manipulating the delay of the haptic and visual rendering. Participants were asked to judge if they first perceived the visual or the haptic rendering when they contacted the virtual wall of 331N/m or 83N/m stiffness. The results show that performance in the no-constant velocity task is strongly affected by the stiffness, whereas in the constant velocity task, participants seemed to perceive delays correctly.