In April, Teatreneu comedy club in Barcelona installed tablets on its seats that detect when patrons smile. And it seems to be paying off.

The BBC reports since it's been implemented, ticket prices are up by six euros.

In fact, the experiment appears to have been such a success that other theaters in Spain are now following suit.

According to the comedy club's website, entrance to its shows are free but each laugh costs 30 euro cents for a maximum charge of 24 euros.

The theater experimented with pay for laugh after a large tax increase on shows led to dwindling audience numbers.

One London comedy club director quipped to the BBC, "Sounds fun, just so long as all the facial recognition data doesn't get forwarded to the NSA."

But a CNET writer pondered whether the technology would introduce too much rationality into comedy clubs, asking: "Might it be the case that later acts will suffer, because patrons will become stingy with their laughs?"

It's not the first time facial recognition technology has been put to commercial use.

In 2010 CBS reported on a vending machine that used the technology to dispense ice cream in exchange for a smile.

And in 2012 DigInfo TV reported on a marketing service that used facial recognition to predict the age and gender of customers to analyze consumer trends and behaviors.

This video includes images from Getty Images.