[Brian Strappini]

Brian Strappini asked the Naked Scientists:
   
If you hold your hand in hot water that's just bearable and then add cold
water. The water seems to rise in temperature so you have to remove your hand.

Is this my imagination or is there a scientific reason for it.

What do you think?

[Kryptid]

This is a real phenomenon and it was mentioned in my college psychology book. I also believe that it was shown on Bill Nye the Science Guy. It is caused by the way that our nerves are wired up. Our hands don't really have "hot" sensory nerves in them; only "warm" and "cold". In order for you to sense "hot", both the "warm" and the "cold" sensors have to be stimulated simultaneously. The experiment you mentioned does exactly this.

[Raghavendra]

It's not only the temperature but the effect of the hand which sense it....