What's up with all those lame "Stay True to You" anti-pot billboards all over the city? I hear when Big Tobacco had to run anti-smoking ads, they used market research to deliberately create the worst ads possible. Is that what's going on here? —Not Impressed

I assume you're referring to the Philip Morris company's infamous "Think. Don't Smoke" campaign, which I think about often and totally did not have to look up in any way.

A 1999 comparison of anti-smoking ads rated "Think. Don't Smoke" dead last in effectiveness, and cynics suggested the tobacco giant had cooked up a toothless ad on purpose.

Did they? "Think. Don't Smoke" does tend to present the issue as a binary choice between smoking and doing something many Americans would rather not do. (Other options might have included "Floss. Don't Smoke,""Eat Kale. Don't Inhale," and "Why Smoke When You Could Be Getting That Long-Overdue Prostate Exam?")

Sincere or not, science shows that even the best anti-smoking propaganda usually doesn't work. Pictures of decaying gums merely trigger smokers' well-developed "la la la I'm not listening" reflex—and if you do manage to scare us, the stress just makes us want a cigarette.

All of which suggests that the "Stay True to You" ads have an uphill climb—especially with squishy tag lines like, "Being a teenager is hard enough. I'm not sure pot would help." Not sure? But it's worth a shot, right? You never know until you try!

In any case, the ads are real. They're paid for by the Oregon Health Authority, which is worried about research showing that young teens and preteens who use marijuana are more likely to have trouble with learning and memory.

Still, there's a bit of a chicken-and-egg problem here—how do we know that the kids who smoke pot weren't dumb to begin with? Maybe that's a more effective message: "Don't worry, kids! Pot doesn't make you dumb—it's just something that dumb kids do. Want some?"

QUESTIONS? Send them to dr.know@wweek.com.