Temporal detection threshold of audio-tactile delays under conditions of active touch with and without a visual cue

While much research has been conducted on multisensory interactions in passive touch, research on how active touch influences how the senses interact remains scarce. Using a haptic surface based on ultrasonic vibrations, we investigated the perception of synchronization of audio-tactile stimuli in active touch. Tactile stimuli were delivered upon sliding the finger, and auditory stimuli followed with a delay ranging from 0-700 ms. In this simultaneity judgment task, two visual conditions were employed: (i) a visual cue showing the location of the active zone on the screen; (ii) a black picture on the screen. We also consider two sliding directions: (i) right-to-left (RTL); (ii) left-to-right (LTR). We estimated the psychometric function (threshold and slope) of the ability to judge whether the auditory and tactile stimuli were temporally synchronous. We found a threshold of 201.26 and 211.73 ms for LTR and 233.3 and 207.23 ms for RTL with and without visual cues, respectively. We translated temporal delays into distances (mm) using the finger sliding velocity measured for each trial. The results indicate that the simultaneity judgment was independent of sliding velocity. Our results provide insights into participants’ sensitivity in perceiving simultaneous audio-tactile feedback generated during active touch exploration.