The Latin verb illudere, meaning to deceive or mock, is the root of the English word illusion.
One of the simplest ways to detect how focused a person's brain is is to show them an optical illusion picture.
Researchers in the field of neuroscience have also studied the brain's reality perception using images of optical illusions.
Some research suggests that solving optical illusion puzzles on a regular basis can help people become more creative thinkers and problem solvers.
Above, you can see a grid of emojis representing clowns laughing. A sad emoji, though, stands out.
Readers are challenged to find that sad emoji within four seconds. You will need to be observant to complete this task.
Is that the sad emoji you saw? The sad emoji is easier to spot for readers with superior visual abilities.