Principle of least astonishment

In user interface design and software design,[1] the principle of least astonishment (POLA), also known as principle of least surprise,[lower-alpha 1] proposes that a component of a system should behave in a way that most users will expect it to behave, and therefore not astonish or surprise users. The following is a corollary of the principle: "If a necessary feature has a high astonishment factor, it may be necessary to redesign the feature."[4]

The principle has been in use in relation to computer interaction since at least the 1970s.[5] Although first formalized in the field of computer technology, the principle can be applied broadly in other fields. For example, in writing, a cross-reference to another part of the work or a hyperlink should be phrased in a way that accurately tells the reader what to expect.