Optical Illusions


These mind-bending optical illusions show how images deceive the eye

Optical illusions are always a hot topic and often cause debates on who’s right or wrong - who could forget the infamous white and gold/blue and black dress in 2015 or the hidden numbers from last month?

We’ve produced some brand-new optical illusions showing again how colours and shapes can trick the eyes.

These were put to the test, with Brits polled on what they could see within the image. Gala Spins also partnered with Bhavin Shah, Behavioural Optometrist at Central Vision Opticians, to explain how and why we see different images and colours.

     1. Do the lines appear straight to you?


The lines are the focal point of this optical illusion, as they appear to be on an angle when in fact they are completely straight.

Almost half of those asked (45%) said the lines were on an angle compared to the other half who were correct and said they were straight (55%).

Bhavin explains this by saying: “This optical effect is even more striking if the colours are black and white. The difference in contrast of the larger squares (dark vs light blue) affects the appearance/perception of the horizontal line in between each row. Different neurons respond to light and dark differently which impacts the line in between which is usually a colour midway between the light and dark.”


    2. Are the lines parallel to each other?


Almost two thirds (60%) of those asked got this one correct by saying the lines are parallel to each other.

Bhavin comments: “Our brains perceive the angled lines as having a larger angle than the actual angle which changes the perception of the parallel lines. In the real world we use angles like this to help orientation, perspective and depth perception such as looking at train tracks converging in the distance.”


    3. How many boxes do you see?


Depending how your eye views the shaded box, either on top or the bottom, the number of boxes the eye sees is different.

A third of those asked (33%) claimed to see 32 boxes, almost one in five (19%) claimed to see 36 boxes and almost one in six (14%) claimed to see 45 boxes.


  4. Does the square have straight or curved lines?


Astoundingly, over a quarter of those asked (77%) were correct by stating the square has straight lines as when looking at this optical illusion Bhavin says: “Our visual system doesn’t process the peripheral vision in the same as the central vision. The peripheral vision uses fast processing where accuracy is not as important as speed. There is also some image processing that happens in the peripheral retina to enhance contrast so the difference such as a straight line over a series of curved lines are highlighted and the perception altered to make them stand out more.”


The dots that can be seen on this optical illusion where the white lines cross are actually white but appear grey to the peripheral vision, Bhavin explains this by saying: “There are a few theories, it could be that the retinal cells in the peripheral part of the visual collate information over a few cells to provide a visual signal and often “enhance” (or image process) areas of contrast but the intersection of the lines and the colour of the square causes an enhancement of the intersection in the peripheral vision which disappears when using the more detailed central vision.”

Interestingly almost one in five (18%) thought the dots were grey in colour.

Which Optical Illusion was your favourite? Tweet us @GalaSpins