Fig 1.
Haptic flash-lag effect and experimental setup.
(A) A haptic flash-lag effect. One finger moves parallel to the transverse (x-) axis (t1). Then, the “haptic flash” is applied. The two fingers are perceived to be aligned during the flash, when the moving finger has not yet crossed the non-moving finger (t2a), but under spatial alignment the moving finger is perceived to be ahead the non-moving one (t2b). (B) Visuo-haptic set-up; the inset shows the finger holder that held the non-moving finger below the midpoint of the movement corridor. In the first experiment the moving finger was always the right index finger, in the second experiment both index fingers were used as moving finger in alternation.
Fig 2.
(A) Average point of subjectively equal position of the moving object to the non-moving, stationary object (PSE) and (B) judgment precision as assessed by JNDs computed from flash onset position for visual and haptic flashes combined with isosensory (visual or haptic) and bisensory (visuo-haptic) objects. A significant negative PSE (marked by an asterisk) indicates a flash-lag effect. Error bars represents standard errors of the means.
Fig 3.
Average point of subjectively equal position of the moving to the non-moving, stationary object (PSE) computed from flash onset position as a function of the intensity and duration of a haptic flash. A significant negative PSE (asterisk) indicates a flash-lag effect. Error bars represents standard errors of the means.