What is illusory correlation?

It is perceiving a relationship between two things that aren’t actually related, or overstating a weak one. We remember the times they coincided and forget the many times they didn’t, so a pattern appears where none exists.

What is an example of illusory correlation?

Believing a full moon causes strange behaviour: the odd nights that happen to fall on a full moon are memorable, while the equally odd nights on ordinary days — and the calm full-moon nights — are forgotten.

How do you avoid illusory correlation?

Count the cases you tend to ignore — the times the two things occurred apart — and track outcomes systematically rather than from memory. Require a plausible mechanism before accepting that a link is real.

Illusory correlation

Judgement

Illusory correlation is perceiving a relationship between two things when none exists, or seeing one far stronger than it really is. We notice and remember the cases that fit our expectation, and overlook the many that don’t.

Why it happens

Co-occurrences that confirm a belief are vivid and memorable, especially when both events are distinctive or rare. We rarely tally the times the two things didn’t go together, so a few striking coincidences create the feeling of a pattern — and confirmation bias then locks it in.

Examples

Believing it always rains right after you wash the car, recalling the hits and forgetting the dry days.
Stereotypes formed because a rare group plus a rare behaviour stand out together and stick in memory.
Feeling a "lucky" shirt wins games, counting the wins and ignoring the losses.

How to counter it

Look for the missing cases: how often did the two things occur apart, not just together?
Track outcomes systematically instead of relying on memorable coincidences.
Demand a plausible mechanism, not just co-occurrence, before believing in a link.

The deeper point

It is the cognitive root of superstition and stereotype alike — both built from a handful of memorable coincidences and a failure to count the boring non-events. The pattern is real, but it lives in your memory’s sampling, not in the world.

Frequently asked

What is illusory correlation?: It is perceiving a relationship between two things that aren’t actually related, or overstating a weak one. We remember the times they coincided and forget the many times they didn’t, so a pattern appears where none exists.
What is an example of illusory correlation?: Believing a full moon causes strange behaviour: the odd nights that happen to fall on a full moon are memorable, while the equally odd nights on ordinary days — and the calm full-moon nights — are forgotten.
How do you avoid illusory correlation?: Count the cases you tend to ignore — the times the two things occurred apart — and track outcomes systematically rather than from memory. Require a plausible mechanism before accepting that a link is real.

Confirmation bias Frequency illusion Availability heuristic The gambler’s fallacy Bayesian thinking Regression to the mean

Editorial synthesis © ReadGlobe 2026, drawing on Kahneman’s Thinking, Fast and Slow, the Tversky–Kahneman research program, and the primary cognitive-science literature. · Last reviewed 2026-05-29.