VR Phobia Desensitization with Haptics: Dose-Response Curves for Vibrotactile Cues in Graded Exposure

Virtual reality exposure therapy provides a controlled, adjustable method for phobia desensitization, but treatment effectiveness depends on careful calibration of exposure intensity. This study evaluated vibrotactile haptics as a graded design variable in VR phobia treatment, emphasizing dose-response effects across exposure stages. Participants completed repeated VR exposure sessions under four haptic conditions: minimal or no haptics, low-dose feedback, moderate-dose feedback, and high-dose vibrotactile cues. Feedback varied in amplitude, duration, and timing, including event-linked and sustained vibration patterns. Outcomes included fear activation, habituation, progression, early termination, perceived control, presence, workload, and acceptability. Results showed a non-linear dose-response relationship. Moderate feedback produced the strongest therapeutic and usability profile by increasing engagement and fear activation while remaining tolerable enough to support progression and habituation. Higher doses increased realism and arousal but also caused distraction, overload, and greater early-termination risk. Carefully calibrated haptics may therefore strengthen VR phobia treatment across diverse users and stages.