Why do people behave like idiots?

By Gordon Rugg

Other people frequently appear to behave like idiots. As is often the case, there’s a simple explanation for this, and as is also often the case, the full story is a bit more complex, but still manageably simple once you get your head round it.

First, the simple explanation. People usually behave in a way that looks idiotic for one or more of the three following reasons:

  • Sin
  • Error
  • Slips

This model comes from the literatures on human error and on safety-critical systems; there are variations on the wording and on some of the detail (particularly around slips) but the core concepts are usually the same.

  • Sin (or “violations” in the more common version of the name) involves someone deliberately setting out to do the wrong thing. I’ll return later to possible reasons for people doing this.
  • Error involves people having mistaken beliefs; for example, they believe that closing a particular valve will solve a particular problem.
  • Slips involve someone intending to do one thing, but unintentionally doing something different; for example, intending to press the button on the left, but accidentally pressing the button on the right.

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