What you need is 3 bowls, some water and something to heat it up.
In 1st bowl put very cold water, the coldest you can find
In 2nd bowl put medium water around temperature of your body, whatever is the most comfortable for you
In 3rd bowl put very heat water, but not too much because you'll put tour hand there.
Differences in temperature between that 3 bowls should be easily recognisable.
Now put right hand in cold water and left in warm water (or opposite). Keep it there for 3-4 min and then put both of them to the medium bowl.
How is the feeling?
