If your house or even your neighbourhood café had walls like the image, you would probably question its structural integrity. When you take a look at the bricks, it appears to be off centre, so to speak. However, when you really look closer, or look at each row individually, you will notice that the bricks are actually perfectly parallel.
How? This design has been created by Selco Builders Warehouse and is a classic example of the café wall illusion. This illusion has been confusing observers for decades trying to find the secret.
One of the people who were intrigued by the fascinating wall, was British psychologist Richard Gregory who noticed this phenomenon in real life in the 1970s. Upon his visit at a café on St. Michael’s Hill in Bristol, he came across the mortar lines in the tile which seemed to be askew. In a study conducted by the psychologist, ‘Border locking and the Café Wall illusion’, Gregory found that the wall’s appearance was a consequence of how the tiles were arranged.
Read the full study here [PDF].
Instead of being stacked neatly in a row, the bricks have been placed offset by half a tile. The colours of each column has also been positioned from dark to light. Though the horizontal mortar lines were parallel to the ground and to each other, this pattern made them look slanted.
You can also experience the illusion for yourself thanks to Selco who has recreated the effect with a trippy illustration. In a study conducted in 2005, it explained why a person sees the illustration as it is. According to the study, the faulty perception of the lines is likely a result of how the neurons in our brain's visual cortex interact to determine orientation. However, what makes it more mind-blowing is that experts still can’t determine exactly how the illusion works.