To the author, caffeine, theobromine and theophylline are all methylxanthines and all function as stimulants since they block inhibition by adenosine (another methylxanthine and part of ATP). However, they are not equal, caffeine is transported into the brain very well, theobromine somewhat and theophylline not so well. That is why, despite the all doing pretty much the same thing biochemically we take caffeine to wake up, theobromine to feel a little more alert but also relaxed, and theophylline to kick up our heart rate and block brochoconstriction in asthma. I am not sure about the other sources, but the methylxanthne chocolate is primarily theobromine, not caffeine. I think if you want to sound scientific in your posts, it might help to actually research your topic somewhat.