Open An Umbrella Indoors Day

What the day is

Open an Umbrella Indoors Day is observed on March 13. It was devised as a test: open one indoors, note whether anything bad follows, and treat the superstition as a claim that can be checked.

Origin and background

The superstition's origin is disputed and probably mundane. The most plausible account is practical rather than mystical: Victorian umbrellas were large, stiff and sprung with metal ribs, and opening one in a crowded room genuinely did break things and injure people. A sensible household rule hardened into an omen once the reason was forgotten. Grander explanations involving sun worship in ancient Egypt are offered but rest on little.

The day's framing points at something real about how superstitions survive. They are typically unfalsifiable in practice, because misfortune is common enough that any subsequent bad event confirms the rule, while an uneventful week is not registered as disconfirming it. That is confirmation bias working with a very generous definition of evidence.

Researchers have found that superstitious behavior tends to increase under uncertainty and low control, which is why it clusters around exams, sport, fishing, aviation and performance rather than around predictable activities. It is a response to not being able to influence an outcome.

There is an awkward footnote. Experiments have reported that superstitious rituals can slightly improve performance on skill tasks, apparently by raising confidence rather than by any effect on the world. So a lucky charm may work, in the narrow sense of making the person holding it steadier, which is a genuinely odd result to sit alongside the rest.

The thirteenth of March, in a month where the thirteenth sometimes falls on a Friday, is a deliberate choice.

How to take part

• Open one indoors, mind the lightbulb, and note what actually happens.
• Check whether your own superstitions cluster around things you cannot control.
• Notice the confirmation bias next time a bad day follows a broken rule.
• Keep the lucky charm if it steadies you. That part appears to work.
• Look up why Victorian umbrellas made this a sensible house rule.