In science, the informal principle of least astonishment, also known as the principle of maximum boredom states that the explanation which is the least astonishing and which is the most boring is usually (but not always) the right one. This can be thought of as an amalgam of Occam's razor and a presumption in favour of current theories.

In user interface design and ergonomics, the principle of least astonishment states that systems should be designed so that users will be able to understand the system's responses to their actions, even when a response is not what the user wanted.

See also: Wikipedia:Principle of least astonishment.