42 here, raised on the U.S. East Coast, lived all over the country since then.
I’d never heard it before, and despite thinking of myself as having a fairly sophisticated sense of humor, it made me snort out loud. 
it might be interesting to see if those with an agricultural experience are more likely to have known about it; than those without.
Not to my knowledge. Not by the uninformative phrase “smart pills”.
ETA: OK yeah, now that I"ve googled it.
Likewise. 40s, SoCal.
No, 33 from VA. I didn’t even recognize it after I’d looked it up. I’ve heard plays on a similar concept, but not close enough to consider them essentially the same joke or derivative. It definitely seems like an old joke though, I had much crasser ones when I was young.
Not googling, so not voting, I guess…
(You could’ve spoiler-box’ed it. Not clear why us reading the joke would spoil your thread)
I’d heard it before, but I only figured that out after Googling it. It’s not a particularly memorable joke to me.
Never heard of it, not familiar with it after googling, and I’m also in the 45-54 range originally from Philadelphia.
I had to google. If I’ve heard it before, I don’t remember it. But I doubt I will remember it much after today. So, maybe?
fifties, northeastern US.
Forgot to mention that I’m 30 and from the Ozarks. I only saw the joke online. I can only imagine it being a kids’ joke, and I wasn’t into that type of humor as a kid.
Mid-forties here, raised in New England - never heard it.
Had to google it, so I’m just assuming it’s the right joke.
No, never heard it. Grew up in Western NY, 48.
Here’s a link to the joke: http://jokes.cc.com/funny-kids/331mek/smart-pills
Thanks, ITD. I wasn’t going to Google it either. I don’t see why the OP couldn’t have put the joke in a spoiler box, either.
I haven’t heard that particular version, but I heard one about a doctor giving a placebo to a patient.
58 years old and grew up in PA. I’ve also lived in Arizona and Colorado.
Nope. Mid-fifties, grew up in Chicago, now live in NY state.
Never heard it. 52, grew up in Toronto, Ontario.
Heard as child in Alabama in the 1980s (slightly different than version linked, but close enough).
No. 47, New York State
I heard it as a kid (NJ, 1970’s), but so long ago I didn’t remember it before googling it.
Yes. 64. Western Canada.
I remember my father telling that joke. The same ending, but with more story. This was in the 50’s in Southern Utah.