If we put a frog in a pot with boiling water, immediately it tries to escape. But, if we put that frog in room temperature water, and we don’t frighten it, it remains quite. When the temperature is changed from 21 to 26 degrees, the frog does nothing, and it even seems to be having fun. The more the temperature increases, the more stunned the frog is, and finally it cannot go out from the pot.
The frog stays in the pot and it is cooked, although nothing prevents it to exit from the pot. Why? Because its internal system to detect threats in order to survive is prepared for sudden changes in the environment, but not slow and gradual ones.
In The Fifth Discipline, of Peter Senge.
Seen in ¡Que paren las máquinas! (allí está en español).