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Rachel Foster, Annika Januszewski, Volker Franz; Incorrect haptic feedback in 50% of trials is sufficient to bias grip aperture. Journal of Vision 2015;15(12):1150. doi: 10.1167/15.12.1150.
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© 2017 Association for Research in Vision and Ophthalmology.
Grasping behavior is being tested increasingly often in virtual and mirror setups. In displays where the visual percept does not correspond to physical reality (e.g., distorted depth perception under limited cue conditions) an important methodological question is what and how much haptic feedback to provide. While grasping without haptic feedback has been shown to drift, both in position and aperture size (Bingham, Coats, & Mon-Williams, 2007, Neuropsychologia, 45, 288-294), grasping with terminal haptic feedback that does not correspond to the visual information has been shown to bias both reaching distance and maximum grip aperture (MGA) in the direction of the haptic feedback (Mon-Williams & Bingham, 2007, JEP:HPP, 33, 645-656; Coats, Bingham, & Mon-Williams, 2008, Experimental Brain Research, 189, 211-220). An ideal balance would be to find a level of haptic feedback that allows for natural grasping, while not biasing behavior. Because presenting correct haptic feedback on 50% of trials has been shown to produce normal grasping (Bingham et al., 2007), we therefore tested whether providing haptic feedback that differed from visual information by 5mm on 50% of trials would bias MGAs in the direction of the haptic feedback. We found that incorrect feedback on 50% of trials did appear to bias grasping (N=32). We additionally noticed that MGAs decreased over time even when correct haptic feedback was presented 100% of the time. We believe this may have been due to participants’ initial uncertainty in the mirror setup, which decreased over time. Our findings underscore the difficulty of providing haptic feedback that does not bias the grasping response. Changes in the grip aperture found in the 100% correct haptic feedback condition also highlight a potential difficulty in defining baseline grasping behavior when using mirror setups.
Meeting abstract presented at VSS 2015
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