There are three situations under which marijuana can be shown to weaken general psychological performance in lab subjects. They are:
(1) By giving it to persons who have not ever had it before;
(2) By giving people very high doses that they are not utilized to (or giving it orally to persons utilized to fuming it); and (3) by giving people very hard things to do, particularly things that they have never had the chance to perform while under influence of drug. Under any of these three ...