Perform Optical Illusions as Magic Tricks (2024)

Imagine that you are sitting on a train. You look out the window and believe that the train is moving. You soon realise that in reality, the neighbouring wagons are moving. After your train finally leaves, you look through the back window, and it seems like the tracks physically meet in the distance, although you know with certainty that they are perfectly parallel to each other. This anecdote is examples of illusions as we experience them in everyday life.

Psychologists have studied the nature of optical illusions to understand how our brain is cheating itself. The study of these illusions also has practical implications. For example, factory control rooms contain many complicated dials and displays that help operators make correct decisions. Engineers design these instruments, so there is no misunderstanding how to interpret the information they display. Another application can be found in traffic engineering. Roads must be designed so that visual information is correctly understood by the driver to reduce the likelihood of accidents.

Optical illusions are also deliberately introduced to avoid perceptual errors. Ancient Greek architects formed stone pillars in a gentle curve with their base slightly wider than the top, so that they seem perfectly straight. Optical refinements to simulate geometric perfection are common in Doric Greek temple architecture. The Parthenon on the Acropolis of Athens is admired for its architectural perfection. To realise this perfect geometry, the architects Ictinus and Callicrates have curved almost every line in the design and created the illusion of straight lines and geometric perfection.

Scientists have systematically studied optical illusions since 1855, the year when the German psychologist Joseph Oppel published an article on the subject. Since that first publication, thousands of books and journal articles have been written on the topic.

One of the simplest illusions is the Müller-Lyer illusion. The horizontal lines have the same length, but the arrows inward or outward confuse the brain because the horizontal lines do not seem to be the same size. The German psychologist Franz Carl Müller-Lyer first published this illusion in work on fifteen geometric illusions.

The Ponzo Illusion is similar to the first example. The converging oblique lines distort our perception of identical horizontal lines. The angled lines cause our brain to recognise the upper line as slightly smaller than the lower one. This illusion is named after the Italian psychologist Mario Ponzo.

If two circles of the same diameter are surrounded by larger and smaller circles, they appear to be different in size. This deception was discovered by the German psychologist Hermann Ebbinghaus. The presence of smaller or larger objects affects our perception of size. This illusion can be used in real life to make portions of foodappear smaller than they are. When a chef serves a meal on a giant plate, it seems smaller than when placed on a standard plate.

The last example here is the Poggendorff illusion, first described in 1860. In this illusion, a rectangle covers an oblique line. Although the diagonal line is straight, it seems as if the line is unequal. This illusion was designed by Johann Zöllner, but it was named after Johann Poggendorff, the publisher of the journal in which it appeared.

Although these phenomena have been studied for more than a century, the actual cause of these deceptions is still not fully certain. There are several competing explanations of how the brain causes them. However, none of thesetheories is universally accepted by psychologists.