CNN Piers Morgan Live March 22, 2014 07:25:00
>> 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 effects will be disruption in memory, disruptions in inhibitory control. they will become slower at cognitive functioning, a wide range of things. these effects are temporary, but they're pretty pronounced, and they are cle...