Clustering illusion – the tendency to see patterns where none exist.
Michael Blastland and Andrew Dilnot write about this in their excellent book about numbers called ‘The Tiger That Isn’t’.
They suggest you throw a bag of rice into the air and watch it fall onto the carpet. See what happens. You will have created a chance distribution of rice grains over the carpet. One thing the grains probably won’t do is scatter evenly. There are likely to be thin and thick patches. And every so often a larger pile of rice will have clustered. The truly weird result would be if the rice had spread itself in a smooth regular layer.
The rice experiment illustrates our tendency to see patterns where actually none exist. The authors conclude that “chance is heartless”.