Serendipity Out of one's depth
Simon Singh is an author, journalist and TV producer, specialising in science and Mathematics. His latest book is "Trick or Treatment? Alternative Medicine on Trial", co-authored with Edzard Ernst, the world’s first professor of complementary medicine.
Sunday 25 July 1999
The principle of the autostereogram, as it is officially called, was discovered in the 1840s by the Scottish scientist Sir David Brewster. He had studied optics for many years, and was responsible for inventing both the kaleidoscope, a big hit among Victorian children, and the lenticular stereo-scope, which became a craze after it fascinated Queen Victoria. The stereo-scope generates a 3-D effect when the viewer looks through the eyepieces, but the beauty of the autostereogram is that a 3-D image is created without any external help - the viewer simply stares at the autostereogram and uses internal brain machinery to give the image depth.
The brain is continually trying to convert signals from the two eyeballs into a meaningful image. For example, if both eyes are focused on a single dot, then the dot will make one signal in each eyeball, and the brain combines the signal in each eyeball in order to work out the exact location of the dot.
However, if both eyes are staring at two dots, say an inch apart and 12 inches from the face, then the situation becomes much more complicated. The two dots create two signals in each eyeball, and the brain does not know which dot in one eyeball is related to which dot in the other eyeball. This ambiguity means that the brain can interpret the information in two ways. It thinks that either the dots are roughly the same distance away, which would be accurate, or that one dot is closer than the other, which results in an artificial sense of depth. The latter interpretation gives the Magic-Eye effect.
Brewster first became aware of how this con- fusion can generate an autostereogram when he was staring at some wall-paper that consisted of a repeated pattern. Instead of interpreting the repeated pattern as flat, his brain mismatched the signals in his eyeballs and created 3-D wallpaper. Men standing at urinals, staring at a wall covered in patterned tiles, sometimes experience a similar accidental autostereogram.
The vast majority of brains try to force eyeball signals into a 3-D framework, which is why a 2-D pattern sometimes seems to have depth. However, roughly 2 per cent of brains are completely lacking in stereovision. Furthermore, another 6 per cent of brains have partly defective stereovision, and those people may or may not be able to appreciate autostereograms.
If you are unsure as to whether or not you have experienced the Magic- Eye effect, then I would offer a remark made by autostereogram expert Chris Tyler: "Stereovision is like love. If you're not sure, then you're not experiencing it".
Final Top Gear reviewTV
Arts & Ents blogs
- 1 BBC told new political editor must be 'impartial' with Nick Robinson reportedly stepping down
- 2 Number of young homeless people in Britain is 'more than three times the official figures'
- 3 Humans of New York image of crying gay teen receives best response yet from Ellen DeGeneres
- 4 The map showing the most dangerous tourist destinations in Europe, according to the Foreign Office
- 5 Swedish minister gives strongest case yet on why EU should stop turning away asylum seekers
More Britons believe that multiculturalism makes the country worse - not better, says poll
Nathan Collier: Montana man inspired by same-sex marriage ruling requests right to wed two wives
Greece crisis: IMF was pushed around by Angela Merkel and Nicholas Sarkozy – and now it is being humiliated
Forget little green men – aliens will look like humans, says Cambridge University evolution expert
Girl, 7, stares down hate preacher at Ohio festival with pro-LGBT rainbow flag gesture
Osborne to cap family benefits at £23,000 – announced ahead of his post-election Budget