The original purpose of the dunce cap was not to mark someone as an idiot. Rather, it served the same purpose as a wizard's hat... a literal "thinking cap." By keeping one of your channels of attention focused on the top-back part of your head, your other channels paradoxially become more focused on the studying at hand. This is outlined in the PhotoReading book as the "Tangerine Technique." Seeing as you may have true ADD, consider actually GETTING a "thinking cap" to focus your attention there. The Chinese Civil Service during the time of Confucius used caps like this for just that very purpose. Being as I am from Wisconsin, I find a foam cheese-wedge hat helps somewhat. (Yes, I've used this. My tangerine kept evaporating).
Your feild of vision also widens because your "center" is further back. It's like holding the book an extra foot away, but without suffering the apparent reduction in text size that such an action would produce.
Also, remember to study in small blocks. While 30 minutes was found to be ideal (5 minutes to get into state, 20 minutes of study, 5 minute break after that), you might wish to use smaller blocks to keep your attention focused. Play with it, and see what works best for you.
Make sure to do research before you accept any medication.
Note, none of my advice is of a medical nature, and is not intended to treat, prevent or cure any illness. The above message has not been evaluated by the FDA.