A new picture has been doing the rounds.

You might recall how back in February this year a debate over one particular dress and its color went viral (I mean global). Was it gold and white or was it really blue? Ok, it wasn’t the debate of the Century; it wasn’t as if the World held its breath while JFK debated the Soviet missile crises; or in more recent time; whether global warming is a fad. But not to take too much away from the dress Kerfuffle, celebrities like Taylor Swift, Ellen DeGeneres, Will Smith's son Jaden and the Kardashians joined in the skirmish.

More recently, a new picture has been doing the rounds. If you look at the picture above and focus on the girl’s eyes for a say 5 or 6 seconds; then look at the empty area to her right; what do you see?

The optical illusion works by using a technique called ‘negative afterimage’. The eye’s photoreceptors identify colors and code them.

We have three color channels, gray-scale, red and green and blue and yellow, which allow us to code color in any environment. When looking at a specific color, the cells in the relating color channel increase in activity. However, after a short while, the activity of these cells decline.

When we direct our gaze at a uniform background; the white box these cells do not return to their resting activity state, instead they go to a much lower state.

It's that decline; the weakening of the yellow code - that codes for the opposite color to become stronger, so you'll see blue. Therefore, in the illusion above, our blue receptor cells decline, which stimulates the opposite hue, yellow. This in turn allows us to see a more natural skin tone and balances out the negative image to reveal the opposite.