If you walk around the river houses on a Saturday night, students say, you can smell the odor of marijuana wafting through the air.

But despite a recent study showing that heavy marijuana use impairs test scores, some students say they will continue to smoke up--primarily for social reasons.

A study released last week by three researchers at McLean Hospital, a Harvard-affiliated hospital, shows that college students who smoke marijuana heavily suffer from a decrease in cognitive abilities--even 24 hours after having last used the drug.

The study compared students who use marijuana an average of 29 days per month to light smokers who use the drug one or two days a month. On tests measuring verbal and attention skills, the heavier users fared worse than the lighter users, according to a press release.

The researchers attributed the poor scores mainly to impairment of one's attention span.

But some students say they do not believe the study's conclusions and will continue to smoke without fear.

One senior in Currier House who considers himself an occasional smoker says he enjoys smoking marijuana because he likes the feeling.

"I feel sort of light, like I'm floating," he says.

The senior says he knows several Harvard students who are heavy users but who do not appear to have decreased cognitive skills as a result of their drug use.

"You can still think relatively coherently [after using marijuana]," he says.

Marijuana tends to affect motivation rather than cognition, the Currier senior says.

"The people who are smoking it a lot, while they are smoking, tend to be lazy about things," he says.

But these heavy users are not lazy about continuing to smoke up, he adds.

Other students charge that even light marijuana use can impair cognitive abilities.

An Ivy Yard first year who spoke on condition of anonymity says she believes even light marijuana use can cause cognitive impairment.