Of course, electricity 101. A 12 volt potential is not enough to cause a great current flow through a 10kohm resistor but clean human skin is not a 10Kohm resister, more like 500 ohm. Add water and the surface resistance goes down further.
Ummm, 500 ohms? If that were so, I've had 1/2 amp flow through me. That may be just a little bit fatal! Actually, books I've read place resistance between 10,000 ohms for dry skin and 1000 for worst-case wet, salty skin. I = 12V/500 = 0.024A > 0.01A = pain
Given that a 9 volt battery is barely preceptable when touched to the tongue, I wouldn't think that there'd be such a huge jump in sensitivity for a 33% increase in voltage.