Unaware haptic perception is often inferred but rarely demonstrated empirically. In this paper we present evidence for the effects of unaware haptic stimuli on users' motor interaction with virtual objects. Using a 3D hapto-visual virtual reality, we ran a texture-difference recognition test in which subjects glided a pen-like stylus along a virtual surface with varying roughness. We found that subjects were not aware of changes in texture roughness below a threshold limit, yet the normal force they applied changed. Subjects did not recognize on a cognitive level changes in the sensory cues, but behaved as if they did. These results suggest that performance can be affected through subliminal cues. Based on results from visual perception studies, we also tested the impact of context background conditions on the perception of unaware cues. We measured the threshold of awareness to changes in texture for several reference stimuli. We found that indeed, as in visual perception, this threshold for discriminating between the roughness of surfaces increases when the texture gets smoother, that is, sensitivity changes as a function of the background context. The implications of this work are mainly in the design of VR, especially for the remote manipulation of objects.

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