It's one of those games you can't imagine playing with people who have been drinking. As part of their 420 coverage last week, producers from Jimmy Kimmel Live took to Hollywood Boulevard and lined up panels of three people, and they made sure one in each group was high. From his studio, Kimmel had to figure out which one.

I certainly couldn't figure it out myself and neither could Kimmel. He asked them questions he thought would show they were high, and he even looked at close-up shots of their eyes. He interviewed two separate groups of three bystanders, and got it wrong both times.

It was a funny segment, worth watching for that reason alone. But there's also something encouraging and noteworthy about it too. It showed that someone who had smoked marijuana or consumed an edible could function in a group of people who hadn't, and even be interviewed on national TV without giving it away. The stereotyped notion of the slow-witted, dazed pot smoker didn't hold in this case. The people were high, but not obviously so.

There is a downside to this, of course, that any law enforcement officer would spot right away. Most people who smoke marijuana think it's a bad thing to get high and drive, as our recent Environics poll discovered, but a relatively high number thought it was okay. So it's not necessarily a good thing that you can't easily spot someone who is high, in the same way you can when someone's had a few drinks or more.

As more U.S. states and countries around the globe look at legalization, governments and researchers are looking for reliable roadside testing procedures, as are already in place for drunk drivers.

In any case, Kimmel's interviews were pedestrians flagged down on the street. Watch for yourself and see if you have better luck spotting the ones who are high.