Optical illusions are older than you think. The first optical illusions date back to 20,000 BC and took the form of cave sculptings. Nowadays they are found all over the place – on screens, in books ...

Martin Doherty received funding from the British Academy/Leverhulme Trust who partially supported this work. He continues to receive funding from the Leverhulme Trust. Radoslaw Wincza does not work ...