Mulan,
That is exactly the reason why a DOUBLE blind test is necessary. This helps eliminate experimenter bias. You are not supposed to know what the patient is holding either. The best circumstance would be for nobody in the room to know. The food item or metal or whatever could be put inside a box so no one can see inside. Of course you'd also have to account for weight and smell and other controls. Unfortunately it is not easy to do a double blind experiment, but only when you have full control can you see what is really happening. This is standard practice in any good science experiment.
No one, to my knowledge, has ever discounted that seeing negative and positive pictures can change muscle response. That seems pretty reasonable.
That sounds nice and all, but it's just a folk-wisdom story. It's not based on fact. The fact is that many herbal remedies are being pulled from the market or are being scrutinized because they are shown to not only be inneffective, but also dangerous because their potency is not stringently controlled. Add that to the fact that they can interact with other drugs and you see a potential for danger to an uneducated public. Herbal medication is just a fad in a long list of alternative remedies throughout history. It will go out of style, just like every other alternative health practice that you addressed above in the quote. It is the scientific method and double blind tests that has proven those former health remedies to be snake oil. The scientific method is still doing it today, but like you said, people will believe no matter what the evidence shows. Anecdotes carry a lot of weight with most people. If it helps you, or someone, that is fine. But the important thing is to understand exactly what is helping the person. Is it really the treatment, or is it a placebo? You wouldn't want to mask a dangerous medical condition with a placebo. That's the danger I see, and it has been documented that lives have been lost in this manner. rem2000 BC
Here, eat this root. 1000 BC That root is heathen. Here, say this prayer. 1805 AD That prayer is superstition. Here, drink this potion. 1940 AD That potion is snake oil. Here, swallow this pill. 1985 AD
That pill is ineffective. Here, take this antibiotic. 2000 AD That antibiotic doesn't work anymore. Here, eat this root....................