The page is actually fairly interesting. It seems to have started with a test where the frog failed to jump out because when it's brain was removed (reminding m

The page is actually fairly interesting. It seems to have started with a test where the frog failed to jump out because when it's brain was removed (reminding me of how frogs go deaf when their legs are cut off). But it does seem that it's a matter of degrees (literally). If sufficiently slow - very slow - the frog may in fact not notice. But it is certainly very slow. It also seems a normal frog will also apparently get bored or restless, and will jump out, not from heat, but because frogs just jump around. Overall, it seems like a hard thing to test for properly without inflicting some constraint on the frog to encourage it to stay and die.