A needle hovers tenuously above your arm. The doctor inexplicably takes his time, telling you repeatedly to expect "a bit" of pain as he delivers the shot. Ever so slowly, he lowers the needle, and excruciating apprehension creeps in before the inevitable poke. You close your eyes, anticipating the pain. Finally you feel the needle prick under your skin and then, suddenly, it's over.
Next time, try keeping your eyes open — it might hurt less.
A recently published study conducted by Matthew R. Longo at the Institute of Cognitive Neuroscience suggests that viewing the part of your body that is subjected to pain actually decreases the unpleasantness you feel. Yes, watching that needle prick your skin might be less painful than turning away and closing your eyes in dread.
Three distinct experiments evaluated the analgesic effects of vision on pain perception in 30 participants between 18 and 34 years old.
In the first experiment, which investigated the effects of non-informative vision, participants would gaze into a mirror (reflecting their left hand or an inanimate object) as their right hand was being stimulated by a low-level laser. The mirror suggested the participant was looking at their stimulated right hand when, in fact, they were looking at the left hand. After the laser pulse, participants rated the amount of intensity and unpleasantness felt.
For the second experiment, the mirror was removed and participants were invited to look directly at their right hand while it was being stimulated. They rated the intensity and unpleasantness then repeated the experiment, this time looking at an object on their left as their right hand was being stimulated.
The third experiment, like the first, used a mirror but participants were looking at the experimenters' hand in the mirror (instead of their own) while the participants' right hand was being stimulated by the laser.
In all of the experiments, participants subjectively rated less intensity and unpleasantness when they were looking directly at the stimulated right hand or when they were looking at a reflection of any hand in the mirror. It seems that viewing the body part directly receiving pain — or even perceiving that you are viewing this body part — decreased the amount of pain associated with the laser pulse.
The study's findings, although from two-armed participants, could be helpful in promoting the use of mirror therapy on acute phantom limb pain (which Lisa Conti explored for Miller-McCune last November).
Mirror therapy, an experimental technique that uses a mirror box to visually "trick" patients into seeing two complete limbs so that they can visually recalibrate an awareness of their own body, has had its share of successstories — although the jury is still out on the effectiveness of the treatment.
But if one simple drop of information is gleaned from Longo's study perhaps it's this: Keep a close eye on your arm the next time doctor's needle looms.
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