Happy Darwin Day! To help celebrate, Rob Jenkins and I have created an optical illusion……

Update: Thanks to The Times for linking to and Stephen Fry for the Tweet-plug!

Rob Jenkins (Univ of Glasgow) and I have created an afterimage illusion with a twist. Because the resolution of an afterimage is not as good as the original, we thought that it might be possible to use fine lines to create an image that looked one way in ‘normal’ vision, and another as an afterimage. And here it is…..

The picture below shows two monkeys. Set your computer monitor to maximum brightness and then stare at the centre of the picture for about 30 seconds without moving your eyes. Next, look to a white wall and blink a few times. The monkeys should suddenly transform into a perfect picture of Darwin!

We thought that it was nice because of the play on ‘adaptation’. In biology, ‘adaptation’ refers to the gradual process by which a species becomes better suited to its environment (e.g., humans and monkeys evolved from a common primate ancestor). However, psychologists use the same term to refer to the perceptual mechanism that gives rise to the negative afterimage in the illusion.

Also, it seemed especially appropriate as Erasmus Darwin (Charles Darwin’s grandfather) carried out pioneering research into this curious optical phenomenon (thanks Tim J.).

There is more about the piece at www.darwinillusion.com.

Feel free to share the illusion with friends and colleagues and, most important of all, have a very happy Darwin Day!