Geometric hallucinations are very common: people get them after taking drugs, following sensory deprivation, or even after rubbing their eyes. What can they tell us about how our brain works?

Why are drug induced hallucinations so compelling that they apparently provided much of the inspiration for early forms of abstract art? Researchers suggest that the answer hinges on an interplay between the mathematics of pattern formation and a mechanism that generates a sense of value and meaning.

How does the uniform ball of cells that make up an embryo differentiate to create the dramatic patterns of a zebra or leopard? How come there are spotty animals with stripy tails, but no stripy animals with spotty tails? Lewis Dartnell solves these, and other, puzzles of animal patterning.
  • Want facts and want them fast? Our Maths in a minute series explores key mathematical concepts in just a few words.