Neuroscience
Our sense of where our bodies begin and end usually feels consistent and reliable. However psychologists have been having fun for decades, exposing just how malleable the body concept can be.
You may have heard of the "rubber hand illusion" (video). By visibly stroking a rubber hand in time with stroking a participant's hidden real hand, you can induce for them the feeling of sensation in the rubber hand.
The rubber hand illusion is thought to occur because the brain tends to bind together information arising from different sensory modalities. The stroking sensation arrives at one's real hand, but the stroking is seen occurring at the same time at the rubber hand. The brain binds these two experiences and the visual modality wins, transferring the felt sensation to the rubber appendage.
Because the rubber hand illusion depends on the dominance of vision, Charles Michel and his colleagues wondered if a similar illusion would still occur for the tongue - one of our own body parts that we feel but rarely see. The researchers purchased a fake tongue from a magic shop (see pic), and for forty seconds they stroked this tongue with a cotton bud (Q-tip) at the same time as they stroked each participant's real tongue. The participants could see the stroking of the fake tongue, but the stroking of their own tongue was hidden from view.
Averaging responses from the 32 student participants, there was an overall sense among the students of being stroked on the rubber tongue, "thus demonstrating," the researchers said, "visual capture over the felt position of the tongue for the very first time." Further evidence for an illusory effect came from the fact that sensation in the rubber tongue was stronger when the stroking of the fake and real tongues was performed in synchrony as opposed to out of time. This synchronous stroking also led to more agreement from the students that they felt as though they could move the fake tongue, and that the fake tongue was their own.
Next, the researchers shone a laser pointer on the fake tongue as the participants watched. Twenty-two of the participants said that this triggered sensations in their real tongue - some said it felt cold, others warm, tactile and/or tingly. "I felt vibrations on my tongue moving in synchrony with the light movement," one student said.
The researchers say their results have shown that an illusion, similar to the rubber hand illusion, can be experienced with the tongue. We call this "the Butcher's Tongue Illusion," they said.
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Michel, C., Velasco, C., Salgado-Montejo, A., & Spence, C. (2014). The Butcher’s Tongue Illusion Perception, 43 (8), 818-824 DOI: 10.1068/p7733
-Further reading-
Psychologist magazine interview with cognitive neuroscientist and ‘master of illusion’ Henrik Ehrsson.
Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.
- Why Do Children Stick Their Tongues Out When They're Concentrating?
Have you ever watched a young child perform a delicate task with their hands and noticed how they stick out their tongue at the same time? A new study is the first to systematically investigate this behaviour in four-year-olds. This isn't just a cute...
- Extras
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- Why The Same Words Keep Getting Stuck On The Tip Of Your Tongue
Not being able to think of a word that you know you know can be so frustrating. What's extra annoying about these tip-of-the-tongue states is that often we'll keep experiencing them for the same word. That's despite the fact that the relief...
- When Castanets Taste Of Tuna
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Neuroscience
The illusion that gives you sensations in a rubber tongue
You may have heard of the "rubber hand illusion" (video). By visibly stroking a rubber hand in time with stroking a participant's hidden real hand, you can induce for them the feeling of sensation in the rubber hand.
The rubber hand illusion is thought to occur because the brain tends to bind together information arising from different sensory modalities. The stroking sensation arrives at one's real hand, but the stroking is seen occurring at the same time at the rubber hand. The brain binds these two experiences and the visual modality wins, transferring the felt sensation to the rubber appendage.
Because the rubber hand illusion depends on the dominance of vision, Charles Michel and his colleagues wondered if a similar illusion would still occur for the tongue - one of our own body parts that we feel but rarely see. The researchers purchased a fake tongue from a magic shop (see pic), and for forty seconds they stroked this tongue with a cotton bud (Q-tip) at the same time as they stroked each participant's real tongue. The participants could see the stroking of the fake tongue, but the stroking of their own tongue was hidden from view.
Averaging responses from the 32 student participants, there was an overall sense among the students of being stroked on the rubber tongue, "thus demonstrating," the researchers said, "visual capture over the felt position of the tongue for the very first time." Further evidence for an illusory effect came from the fact that sensation in the rubber tongue was stronger when the stroking of the fake and real tongues was performed in synchrony as opposed to out of time. This synchronous stroking also led to more agreement from the students that they felt as though they could move the fake tongue, and that the fake tongue was their own.
Next, the researchers shone a laser pointer on the fake tongue as the participants watched. Twenty-two of the participants said that this triggered sensations in their real tongue - some said it felt cold, others warm, tactile and/or tingly. "I felt vibrations on my tongue moving in synchrony with the light movement," one student said.
The researchers say their results have shown that an illusion, similar to the rubber hand illusion, can be experienced with the tongue. We call this "the Butcher's Tongue Illusion," they said.
_________________________________
Michel, C., Velasco, C., Salgado-Montejo, A., & Spence, C. (2014). The Butcher’s Tongue Illusion Perception, 43 (8), 818-824 DOI: 10.1068/p7733
-Further reading-
Psychologist magazine interview with cognitive neuroscientist and ‘master of illusion’ Henrik Ehrsson.
Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.
- Why Do Children Stick Their Tongues Out When They're Concentrating?
Have you ever watched a young child perform a delicate task with their hands and noticed how they stick out their tongue at the same time? A new study is the first to systematically investigate this behaviour in four-year-olds. This isn't just a cute...
- Extras
Eye-catching studies that didn't make the final cut: Danish study: 95-year-olds tested in 2010 had better cognitive functioning than 93-yr-olds tested a decade earlier. Control groups in psychology don't take full account of the placebo effect....
- The Alien Awakened By A Rubber Hand
What happens if you administer a tactile illusion to a brain-damaged patient whose hand is out of their control? A team of researchers has done just that, figuring that illusions could offer new insights into complex neuropsychological disorders. The...
- Why The Same Words Keep Getting Stuck On The Tip Of Your Tongue
Not being able to think of a word that you know you know can be so frustrating. What's extra annoying about these tip-of-the-tongue states is that often we'll keep experiencing them for the same word. That's despite the fact that the relief...
- When Castanets Taste Of Tuna
Words have sensory connotations to most of us. The word leathery really does feel ...well, rather leathery. But to some synaesthetes – people who experience a cross-over of the senses – such analogies are literal and can relate to tastes. That is,...