People who say the can recognize and discount placebos, are often the most susceptible to them, myself included.
I have tested dozens of smart drugs and supplements, and what I find is that before trying them, you don't even know what the particular cognitive benefits will be for each individual dug or supplement. You only tend to observe the benefits sometimes months later, while engaging in particular cognitive tasks.
For example, I initially thought acetyl-L-carnitine was a useless smart supplement in my case — until one time I tried it while I was writing an essay. I then noticed, just out of the blue, that ALC enhanced my word selection abilities (finding the precise word to describe what your are writing about). Had I not been writing an essay, I would never have discovered this subtle effect. I later found out that ALC has been proven to affect verbal IQ.
Sometimes I found a smart drug or supplement would consistently cause a very negative effect; again, this tends to indicate that you can become aware of the true effects of the drug, since the placebo ("I will please") effect is the expectation of a good effect, not a bad. The fact that, contrary to expectation you can reliably observe a bad effect is again indication that your perception is not clouded by the placebo effect, though no doubt there will always be some placebo effect present.
I know that whenever I am about to try new smart drug or supplement, this invariably puts mew into a more optimistic, more hopeful mood, even before I take the pill. That's a kind of placebo effect; it is down to the expectation of a benefit. However, in cases where the supposed benefit effect turned out to be a negative effect, I seemed able to become aware of it. One smart drug I tried unexpectedly caused significant depression, as an example of a negative effect.
I have always done a lot of mindfulness meditation, and I think this helps you develop a better "inner eye", that is, a better viewpoint and connection to your own mind, which then increases the sensitivity and subtleness of self observation in any of these cognitive experiments.
Mindfulness meditation also significantly improves the subtly of your intelligence anyway, I find, and I would rate doing regular mindfulness meditation as a very effective cognitive enhancer just on its own.
Edited by Hip, 05 December 2012 - 03:02 PM.