Exp Brain Res DOI 10.1007/s00221-010-2422-0 123 RESEARCH ARTICLE Electrotactile stimuli delivered across Wngertips inducing the Cutaneous Rabbit EVect Jay P. Warren · Marco Santello · Stephen I. Helms Tillery Received: 16 February 2010 / Accepted: 9 September 2010  Springer-Verlag 2010 Abstract Previous studies have been unable to induce the Cutaneous Rabbit EVect (CRE) when the most likely per- ceived location of the illusory stimulus is on a non-continu- ous skin area. To determine whether the CRE could be elicited when each of the delivered stimuli were on non- continuous skin areas, we developed a new electrotactile stimulation paradigm attempting to induce the CRE across the Wngertips. Though our stimulation paradigm diVered from classic reduced CRE paradigms through the use of electrotactile stimuli, focusing the subject attention to a ‘likely’ illusory site, and the inclusion of a fourth stimula- tion site (two stimuli after the illusory stimulus), these fac- tors were not the cause of the illusory eVect we observed. Experiments conducted on the forearm validated that our paradigm elicited similar results to those reported in previ- ous CRE studies that used either 3-stimulation-point mechanical or electrotactile stimuli with subject attention focused on the ‘likely’ illusory site. Across the Wngertips, we observed an increase in stimulus mislocalization onto the middle Wngertip, the ‘likely’ perceived location of the illusory stimuli, under Illusory Rabbit Trains compared to the Motion Bias Trains. Because the Motion Bias Trains should not induce a perceived location shift of the illusory stimulus but stimulates the adjacent digits in a similar way to the Illusory Rabbit Trains, diVerences observed between their mislocalization rates between these trains indicate that the CRE can be induced across the Wngertips. These results provide the Wrst evidence that the CRE can ‘jump’ when the stimuli occur across non-continuous skin areas. Keywords Cutaneous Rabbit EVect · Electrotactile · Electrocutaneous · Tactile illusion · Fingertips Introduction The Cutaneous Rabbit EVect (CRE) and other tactile illu- sions indicate that tactile perception goes beyond the verid- ical representation of mechanical stimuli and includes the brain’s interpretation of these stimuli (Eimer et al. 2005; Blankenburg et al. 2006; Flach and Haggard 2006). The CRE is a subset of a larger class of tactile saltation illusions that are elicited when a mechanical stimulus is applied at one location followed by similar stimuli at nearby locations in a very rapid fashion. The reported location of each rap- idly applied stimulus shifts from the actual stimulation site toward the following stimulation sites in a predictable man- ner depending on factors such as stimulus location and frequency (Geldard and Sherrick 1972, 1983; Cholewiak 1976; Geldard 1982b; Cholewiak 1999; Flach and Haggard 2006). Geldard (1977) created a reduced form of the illusion using mechanical stimuli at three locations. The Wrst stimu- lus, located at L1 at time t1, is referred to as the locator stimulus and establishes the spatial and, perhaps, the tem- poral origin of the stimulation train. The second stimulus, located at L1 at time t2, is referred to as the attractee stimu- lus. This stimulus is the one that is perceived at a diVerent location from where it is actually delivered and is the heart of the illusion. The third stimulus, located at L3 at time t3, J. P. Warren (&) · M. Santello · S. I. Helms Tillery School of Biological and Health System Engineering, Arizona State University, ECG 334, Tempe, AZ 85287-9709, USA e-mail: jaypwarren@gmail.com S. I. Helms Tillery Psychology Department, Arizona State University, Tempe, AZ, USA