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Scientists have come up with a strange ‘time travel’ illusion to show how your senses can be used to trick your brain.
Created by researchers at the California Institute of Technology (Caltech), the illusion involves a series of beeps and flashes.
Calling it a ‘time-traveling illusion [that] tricks the brain’, they say that hearing sounds can influence your brain into seeing things that aren’t there.
Watch the ‘Illusory Rabbit’ video above to see for yourself.
The video asks you to focus on a cross while a short beep and a quick flash are played nearly simultaneously below it.
The flash appears at the left side of the screen and, 58 milliseconds after the first beep, a second beep is played. Finally, 58 milliseconds after the second beep, a third beep is played alongside a second flash.
The second flash appears on the right hand side of the screen.
Though only two flashes are played, most people viewing the illusion perceive three flashes, with an illusory flash coinciding with the second beep and appearing to be located in the center of the screen.
The time travelling illusion explained (Image: Caltech)
‘By investigating illusions, we can study the brain’s decision-making process,’ explained Caltech’s Noelle Stiles, the lead author of the study.
‘For example, how does the brain determine reality with information from multiple senses that is at times noisy and conflicting?
‘The brain uses assumptions about the environment to solve this problem. When these assumptions happen to be wrong, illusions can occur as the brain tries to make the best sense of a confusing situation.
‘We can use these illusions to unveil the underlying inferences that the brain makes.’
Intriguingly, the above illusion only works because the information is delivered so quickly that it can overwhelm the brain. All three beeps hit you in under 200 milliseconds (one-fifth of a second).
The researchers say the key evidence to take away is that the illusion is perceived between the left and the right flashes.
‘When the final beep-flash pair is later presented, the brain assumes that it must have missed the flash associated with the unpaired beep and quite literally makes up the fact that there must have been a second flash that it missed,’ explains Stiles.
Your brain gets tricked into seeing things that aren’t there
‘This already implies a postdictive mechanism at work.
‘But even more importantly, the only way that you could perceive the shifted illusory flash would be if the information that comes later in time—the final beep-flash combination—is being used to reconstruct the most likely location of the illusory flash as well.’
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