Anyone who has visited Science Gallery's latest exhibition, HAPPY, will likely have seen a striking image of a upturned man rather pleased with himself. However, if you turn flip the image, so as the young man appears in the right orientation, and again take a look, he doesn't seem at all pleased. In fact, he doesn't even seem recognisable as human.
The striking image utilises a phenomenon known as the Thatcher Effect (because it was first demonstrated using a photo of Margaret Thatcher) - a strange illusion which ultilises specific psychological processes involved in face perception. If we study the images above we can see that with both heads upside - down, the man is instantly recognisable as Barrack Obama. But when turned in the correct orientation, the picture on the left seems unnatural, again almost inhuman. And of course it is - the eyes and mouth have been clearly flipped. But how come we recognised Obama when turned upside-down?
While not fully understood, scientists believe the effect is mostly likely related to how we have evolved processes in our brains to differentiate between different faces. This process is believed to rely on the configuration of facial features like the eyes, nose and mouth. Obviously, these processes have evolved to see faces "the right way up" so, when you flip the faces, the process of differentiation cannot take place. Therefore, the brain is unable to detect the minor changes to the altered image when upside-down but can easily recognise the differences when flipped the right way up.
The brain is a wondrous organ yet we still don't know everything about how it works. It is likely that we will learn more about face recognition with further advances neuroscience.
For more information on the Thatcher Effect, check out this page on the Bang Goes The Theory website.