A tracking protocol was used to conduct a two-point limen threshold test. Separation between the two probe tips on the attended hand (AH) versus time was observed under four conditions of stimulation. One condition consisted of 25 Hz flutter applied by the TPS on the AH. In a second condition, the two tips were applied to the AH by a complex stimulus (25 Hz+200 Hz). For the other two conditions, 25 Hz flutter was applied to the AH with either a 25 Hz flutter or 200 Hz vibration stimulus applied simultaneously to the unattended hand (UH). A single trial consisted of stimuli presented to the skin for 1 sec, and then completely removed from the skin for an inter-stimulus interval of 2 sec. Each run consisted of 30 trials, or a duration of 90 sec total.