>> stop worrying so much about this and that and just sort of looking and being as present as possible. >> amir does caution that it's a delicate balance for him. >> it would make me apprehensive, maybe a little paranoid. just too analytical. >> can you get paranoid and have disorganized thinking. you get disoriented. it can be uncomfortable. it can lead to panic attacks or anxiety attacks in people. >> how do you know when you've done too much? >> simple tasks become very frustrating, like mixing paint, and then just sort of get into this state of, you know -- >> and why that happens is exactly what columbia university neuroscientist carl hart is investigating. >> exhale. >> research subjects in his lab smoke marijuana and then take a variety of cognitive tests. >> the affects will be