The age old experiment of placing a pot in boiling water, or placing it in normal water and then increasing the temp of the water to boiling point.

The boiling frog story is a widespread anecdote describing a frog slowly being boiled alive. The premise is that if a frog is placed in boiling water, it will jump out, but if it is placed in cold water that is slowly heated, it will not perceive the danger and will be cooked to death. The story is often used as a metaphor for the inability of people to react to significant changes that occur gradually. According to contemporary biologists the premise of the story is not literally true; a frog submerged and gradually heated will jump out. However, some 19th century research experiments suggested that the underlying premise is true, provided the heating is gradual enough.

http://en.wikipedia.org/wiki/Boiling_...