Monday, March 26, 2012

classical conditioning and placebo effects

Classical conditioning is a form of learning or physiological change. It is based on forming an association between a stimulus and a response. The association is remembered and affects future similar experiences. Some physiological responses to stimuli are unconditioned: they happen naturally and involuntarily, like blinking, flinching, or the salivation response to the taste or odor of food. Other physiological responses are conditioned: for example, a dog can be conditioned to salivate when a bell is rung because the dog has been taught to associate the bell with food (Pavlov's famous experiment). Dogs injected with morphine begin to salivate and can be conditioned to salivate from any injection, whether with morphine or not.

Relief from pain is often attributed to the placebo effect when no active pain-killer has been administered and the patient reports that the pain has lessened. A more accurate description in some such cases, however, might be that the patient has learned to associate pain reduction with pushing a button that releases morphine or with getting a morphine injection. I know from experience that self-monitored morphine injection devices are designed to prevent an unsafe amount of morphine from being taken. The patient may push the button and feel relief but after a certain amount of morphine has been released, pushing the button does not release morphine despite what the patient might think. People who have been injected with saline solution but think they are getting morphine may feel relief from pain because they are conditioned to expect relief after the injection.

Conditioning and associative learning--along with owner or practitioner expectation and self-deception--might explain why some animals appear to get relief from reiki, homeopathy, or acupuncture. A woman who does reiki on horses wrote me: "Animals have no preconceived ideas about Reiki; no expectations about a treatment. There is no placebo effect with animals." Those who think animals can't respond to placebos should consider that what is sometimes called the placebo effect is actually a conditioned response to a stimulus and it is a well-known fact that animals respond to conditioning. Conditioning does not have to be done consciously, nor does it have to involve acts like clapping or ringing a bell. Nor does it have to involve belief. The rituals a vet or pet owner goes through with an animal when it is injured or ill can have a conditioning effect.

Conditioning can involve much more than obvious factors like getting an injection, taking a pill, or being touched where it hurts. Conditioning can involve the theater of the medical setting and medical rituals, including the medical uniforms worn, medical jargon spoken, and medical gadgetry used. These conditions affect the patient's expectation of relief from the treatment, as does the manner of the healer. Patient expectation, it turns out, plays a significant role in the effectiveness of many kinds of treatment. Classical conditioning is "hypothesized to be the primary triggering mechanism for the placebo effect ... which must be learned before it can manifest itself...." (Bausell 2007: 131). When conditioning is combined with desire and motivation for relief, the placebo effect is boosted for both active and inert substances.

A common misunderstanding regarding placebos is that a placebo must be an inert substance that tricks the patient into thinking he's been given an active substance. Many people think that the placebo effect is "all in the head," but that is no more true than that people's physiological and behavioral responses to what they think is alcohol or a drug are only in their head. People can be conditioned to respond physiologically and behaviorally "to placebos through repeated administrations of active drugs" (Bausell 2007: 132) and to hypnosis through learned expectation.

Antonella Pollo et al. demonstrated that placebos can help people with serious pain and Martina Amanzio et al. (2001) demonstrated that "at least part of the physiological basis for the placebo effect is opioid in nature." That is, we can be conditioned to release such chemical substances as endorphins, catecholamines, cortisol, and adrenaline. One reason, perhaps, that people report pain relief from both acupuncture and sham acupuncture is that both are placebos that stimulate the opioid system.

Donald D. Price, an expert on pain, has demonstrated that conditioning and expectation significantly affect the experience of pain and pain reduction. R. Barker Bausell speculates that since complementary and alternative medicine (CAM) practitioners' greatest asset is their nourishment of hope, "such therapies may be engendering nothing more than the expectation that they will reduce pain by elaborate explanations, promises, and ceremonies" (2007: 149). He also notes that the analgesics prescribed by our physicians receive a boost in efficacy based on our past experience and expectations. Many advocates of energy medicine mistake the effects of classical conditioning, expectation of relief that leads to reduction of anxiety and stress, and beliefs about the effectiveness of energy medicine as being consequences of manipulating a mythical subtle energy.

In her book, Women Aren't Supposed to Fly: The Memoirs of a Female Flight Surgeon, Dr. Harriet Hall tells the story of a vasectomy patient who underwent the surgery without anesthesia because he was mistakenly injected with saline solution rather than lidocaine. She also tells the story of a woman whose severe headaches went away after being injected with saline. The latter swore that only Demerol worked for her, but she had been conditioned to feel relief when she got a shot.

So, the next time you are wondering how healers can cure people with a simple touch or by waving their hands in the air over a body part or by uttering some ineffable incantation, think that maybe, just maybe, some sort of conditioned response is going on. You don't have to call it a placebo response, but if you do, don't assume that classical conditioning is the only explanation for placebo effects. There may be other explanations for some placebo responses and the issue may be more complicated than you think. It is unlikely that the "healer" unblocked chi, evoked the assistance of a supernatural being, transferred her animal magnetism, unleashed a vital force in the memory of water, or erased memories of pain by tapping your tummy. Remember the old saying: when you hear hoof beats, think horses not zebras. Well, when you hear of magical healing, think classical conditioning, natural regression, misdiagnosis, symptom fluctuation, patient politeness and subordination, or a host of other things. Your first inclination might be to think magic or miracle, but first inclinations may be responses to the availability bias. If it's truth you're after, you might want to consider alternative explanations to what your intuition tells you.


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