Eight Illusions That Will Show That You Can't Trust Your Senses At All

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Rosie McCall 24 Mar 2018, 16:10

Shepard Tone Illusion

An audio trick called the "Shepard Tone Illusion" manipulates the brain into thinking the tune continues to ascend in pitch. In reality, it is a musical clip that loops over and over and over, never rising in pitch – as Vox describes it, it is the audio equivalent of a barber's pole.

This works because there are three layers of sound layered on top of one another. The highest pitched layer becomes quieter as the clip goes on, while the lower pitch gets louder and the middle pitch remains constant. Even though the clip is repeating itself and, therefore, isn't actually getting any higher, the listener hears two tones rising in pitch and believes the tune is constantly escalating. The result: a tense, emotional sound – an effect Hans Zimmer frequently employs in his musical scores.

Tritone Paradox

In 1986, Diana Deutsch came up with the "Tritone Paradox", a variation on the "Shepard Tone Illusion". Two tones separated by a tritone or half-octave are played over and over. Some people will "hear" the tune ascending in pitch, whereas others will "hear" it descending.

Both sets of people are wrong because, in reality, it is the same two tones repeating. However, the side of the fence you fall on could say something about your upbringing. Studies have shown that the way the two tones are perceived varies according to a listener's language and dialect. People from Vietnam, for example, will hear the tones differently to people from California. Other studies suggest that even your parent's upbringing can have an influence.

The Rubber Hand Illusion

Phantom limb syndrome affects many people who have had an arm or leg amputated, but even non-amputees can be deluded into thinking they have an invisible hand.

To perform this trick, sit at a table with a screen running through the middle and keep your right hand hidden while holding your left hand out in front of you. Next to your left hand, introduce a rubber hand. If both your left hand and the right hand are stroked simultaneously, your mind might "feel" the sensation on the rubber hand.

The Illusion of Taste

This one is going to require some props, specifically two glasses of white wine and some red food dye.

You might think you can tell your red from your white with your eyes closed, but a 2001 study involving 54 enology students suggests otherwise. The volunteers were asked to describe the flavor notes of two glasses of wine, one white and one red. Words like "honey", "lemon", "lychee", and "straw" were used to describe the glass of white, whereas words like "prune", "chocolate", and "tobacco" were used to describe the glass of red.

The twist: They were describing the same bottle of wine. The researchers had dyed the naturally white wine red in one glass.

If you are not a big wine drinker, you might want to try a similar experiment with chip packets. Charles Spence from Oxford University duped tasters into confusing salt and vinegar chips with cheese and onion chips. He told The Guardian that "many of our subjects will taste the color of the crisp packet, not the crisp itself."


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