I am not sure who did the tweeking, whether it was Alton Brown or Cook's Illustrated but I remeber them doing a bunch of experiments.
For a more crisp cookie, I think it was something like adding more baking soda etc..And adding milk for a softer cookie. I am going to try to find some links....
http://www.baking911.com/cookies/101_tips.htm http://www.post-gazette.com/food/200...es1129fnp1.asp
Hope this helps.