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Can sounds, smells and other subliminal cues influence the body's healing process?

We've written previously about research examining the neurological underpinnings of the placebo effect. Now findings published earlier this week offer new insights into how subconscious cues, such as sounds or smells, may play a role in the body's healing process.

In the small study (subscription required), participants were shown two different images accompanied either by a short, painful heat pulse on their arm or a more milder pulse. Individuals rated their level of pain each time they viewed the images. During a second experiment involving half the volunteers, researchers adjusted the pulse to apply the same level of heat. The remaining members in the group participated in a third experiment where they were shown the images for 12 milliseconds accompanied by the same level of heat pulse. Researchers found that when the heat pulse was equal, volunteers' pain ratings were no different than their responses in the original test, where the heat levels varied.

New Scientist story published today reports on the significance of the findings and the potential of the research being translated into a clinical setting:

"The research shows our behaviour and emotional experiences are often guided by stimuli out of our consciousness," says Fabrizio Benedetti of the University of Turin Medical School in Italy. "Once again, the placebo response is emerging as an excellent model to understand how our brain works."

Jensen says that if we can identify cues that subliminally aid recovery, "such as background smells or simply a firm, reassuring handshake from a doctor", then we could incorporate them into clinical practice. Likewise, we could try to reduce or eliminate people's exposure to cues that can hamper recovery. "The awareness of these mechanisms, and that they operate in most people, is an important first step. The second will be to test interventions that could benefit patients," she says.

Joel Voss of Northwestern University in Chicago is sceptical that we can improve treatment using subliminal cues, however. It would be too hard to generate them in a hospital or clinic, he says.

Previously: Do placebos provide a mental cue to kickstart the immune system?Debating the placebo as treatmentThe puzzling powers of the palacebo effect and The increasing power of the placebo

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