Frog in Boiling Water Fable

If you plunge a frog into boiling water, it will immediately jump out. But if you place the frog into cool water and slowly heat it to boiling, the frog won’t notice and will slowly cook to death. So claims the myth. Indeed, everyone—from corporate consultants to politicians to environmental activists—cites the frog fable as proof that people often don’t see change happening and cannot deal with it in the aftermath.
As with most myths the facts simply don't line up with reality, read more here: http://conservationmagazine.org/2011/03/frog-fable-brought-to-boil/