BRIGHTNESS ILLUSION
What to do: Look at the upper and lower surfaces of the cube above. They appear very different: white below and grey above. Now take a sheet of paper and cut two small holes in it. Place it over the cube so that one hole is above the "grey" topside and one hole is above the "white" underside, and the rest of the picture is hidden. You can now see that the two sides are actually the same colour.
The science bit: Our visual system evolved so that we don't just see exactly what our eyes detect. The brain interprets the light signals the eyes receive and makes a best guess at what is out there based on its past experience. In this case, from our experience of cubes in the real world, our brain assumes that the top and bottom of the cube are illuminated differently, and that the underside is in shadow.
Thus our brain deduces that the underside is, in reality, a lighter colour than the top side, and this is what we "see".
UPSIDE-DOWN FACE
What to do: Look at the photo of me on this page. Notice anything funny? Yes, it's meant to be upside down. Notice anything else? Turn the photo the right way up to see.
The science bit: This illusion shows that we process upside-down faces differently from upright faces. Several experiments have shown that it is much harder to detect differences in features when faces are upside down.
This is true in this example, where you don't notice that my eyes and mouth are the wrong way up when my face is upside down, and also of recognising people. It is much harder to recognise photos of people when they are upside down (try this with photos of celebrities).
One suggested explanation is that faces are perceived by a specialised process in our brains that is different from the one for perceiving objects. This face-perception process is thought to rely on detecting the configuration of the features of the face, rather than identifying individual features, and is believed to be specialised for upright faces, which is the norm.
But when the face is upside down, normal face processing doesn't work, so differences in configuration of the features are harder to spot.
ROTATING WHEELS
What to do: Warning! If it makes you feel nauseous, don't continue. Look at the picture above. The wheels are actually stationary, but they should look like they are moving. If you stare at the centre of a wheel, it should stop and only those in your peripheral vision continue to move.
The science bit: Our visual system contains brain cells that respond to motion. This illusion works because of the differences in brightness between the wheels' stripes. Scientists, including Professor Akiyoshi Kitaoka of Ritsumeikan University, the creator of this illusion, recently found that when monkeys look at this illusion the parts of their brains that detect motion are activated.
Thus it appears that this particular pattern of differences in brightness somehow tricks the motion-detecting nerves in the visual system into responding so that we see motion even though there is none. Prof Kitaoka was awarded this year's L'Oréal Art and Science of Colour Prize for his illusions.
JUMBLED LETTERS
Bivelee it or not, rcesrhaeers at Cmabrigde hvae dirvoseced taht the oredr of ltteers in a wrod deson't rlaley matter. The olny iprmoetnt tihng is taht the frist and lsat ltteer are in the rghit pclae. Eevn if the rset are tolatly julebmd up you can sitll raed it. Tihs is bcuseae the huamn barin deos not raed ecah lteter invuddilialy, but inesatd renisgoecs the wrod as a wlohe.
So terhe you hvae it. You mhigt hvae thgohut taht yuor biran wdulon't be wroikng perplory atfer all the Chsimrats and New Yaer celinratobes, and tehn all tshee ticrks and isollunis smeeed to sohw taht yuor biarn is eslaiy feolod, but tihs autalcly manes taht yoru biran is wkonrig pfretecly nolralmy. Cnogrtaulatoins!
