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One interesting and surprising predictor of intelligence is finger-tapping speed, which turns out to be influenced by the level of dopamine in the brain. Research on the brain's timing system has often pointed to the important role of dopamine in controlling the timing of movement and information processing speed. People who tap their fingers fast usually also think fast, and their increased processing speed correlates with their IQ score - which is not always a good predictor of real intelligence. The obvious prediction then is that these people also have a high level of dopamine in their forebrain. By contrast, people with Parkinson's disease have reduced levels of dopamine in their forebrain, move slowly, and in the advanced stages of the disease, suffer with a bothersome slowing of mental function. Their finger-tapping speed is commensurately slow as well.
To appreciate this idea better, consider your computer. You are likely using a computer that processes data at gigabytes per second; a few years ago, you may have used one that processed at only megabytes per second. Your computer today is not smarter, just faster. Your brain is much like this, and dopamine seems to be responsible for the clock speed that is coupled to your processing speed. Your finger-tapping speed may correlate with your IQ, but consuming stimulants such as coffee to increase dopamine release will only arouse you and speed up your thinking; it will not raise your IQ even one point higher. Now imagine you were to consume marijuana or alcohol, drugs that are known to slow the release of dopamine in the brain. These drugs slow you down and make you act and feel fuzzy-headed. However, when their effects wear off, your IQ has not lost any points - usually.
I was recently honored by an invitation to give a TED talk on this topic area. The video is available here. http://www.youtube.com/watch?v=4SvkaK2Al0o&feature=plcp
Why not just drink lots of coffee and increase your brain's processing speed to the point where you appear to be a genius, even if you're not? The answer is that your brain is probably already functioning almost as fast as is safe. Most of us can push the processing speed a little without risk. Unfortunately, the neural processing speed in our brains is already just a few extra action potentials per second away from a full-blown seizure. Indeed, your brain works so fast that you are always vulnerable to seizures in response to many different stimuli, such as a small head injury, a stroke, rapidly flashing lights, a tumor, and so forth. Given the limitations of our brain physiology and chemistry, we are probably as smart as we possibly can be at this time in our species' evolution.
Overall, your brain is fairly fast, but surprisingly, it's not too efficient, which is probably why coffee can make us perform some tasks a little better. We are pretty much stuck with what our brains are capable of achieving in the here and now, and that capability does not change significantly regardless of the substances we might take to speed our mental performance. Thus far, no one has been able to design a drug that can make a person smarter in any real and long-lasting way, other than temporarily increasing processing speed. So if we look at the so-called memory boosters and cognitive enhancers on the market today, we see that they usually contain some caffeine and sugar that together do very little except pep you up and make you a little poorer. At this point in time in the 21st century, nothing-let me repeat that with emphasis, nothing-exists that can truly make you more intelligent, so save your money and just have another cup of coffee.
Also see: Marijuana and Coffee are good for the brain; http://www.youtube.com/watch?v=2uVXs6CY2ps
© Gary L.Wenk, Ph.D. author of Your Brain on Food (Oxford, 2010); http://faculty.psy.ohio-state.edu/wenk/
