== there may be a lot of subtle issues in the quoted double blind study == 

 The "scientific double blind" that claims "no effect" could have numerous issues. My observations are as follows: 
 I consumed a great deal of sugar products as a kid and I remember there was no obvious effects that outsider could notice but there was definitely a subtle addictive effect - as in a craving for more sugary products after a while. The addiction comes back very quickly after sugary snacks, and the only cure is to not have any sugary products in the house, if there are any, one can't really resist eating them. 

 As an adult I have noticed the "rush" also and this was witnessed on a TV show Survivor as well where the adult who was said to be sugar-free for years, consumed various such products on camera and experienced what I remember experiencing after being a month of sugar free and then consuming *Extreme* amounts of sugar (cooking accident). The effects were very similar, unstoppable giggling (I remember giggling for like 5 minutes straight even though I wanted to stop). Though if you just consume the sugar product and don't have some funny thing to initiate the giggling/laughter, then it may not happen - the point is, once it does start, you have no control over it if you are, clear,y intoxicad with sugar. 

 So proving this scientifically requires quite a bit of preparation and right circumstances. I doubt the studies so far have gone to such effort. It's also possible some people are more pre-disposed to the sugar effects. Personally I find that I have LESS focus to think through out the day when consuming even tiny amount sugar products, it clouds the thoughts for me but this is extremely subtle and you'd have to be doing some very serious intellectual work to notice this effect.