Warning: Necomimi cat ears may not be your thing if (1) you like to blend in with the crowd (they're fuzzy and larger than life-size, and you wear them on your head), (2) you like to be mysterious and inscrutable (they enable people to read your mind) or (3) you don't like to have a good time ("They're a lot of fun," says Stanley Yang, chief executive of NeuroSky, the San Jose company that makes the ears).

The ears come on a headband that contains the microchip that basically runs the show. It's programmed to detect your brain waves, figure out what mood you're in from the speed and amplitude of the waves, and make the ears move in a corresponding feline fashion.

NeuroSky is a leading producer of research-grade biosensory instruments, "and the technology in the Necomimi ears is the same exact technology we put in our other products. Over 400 institutions use it," Yang says.

The Necomimi chip does have its limits. If you're in the mood to have pizza, or see an old movie or buy your pug a new Easter dress, the chip won't figure out those specifics. But, Yang says, it can tell if you're interested or focused on something (the ears prick up), if you're bored or just relaxed (the ears droop) or if you're happy, in the zone (they wiggle back and forth).

"There are a few other states we program in too," Yang says, "but we leave it up to people to guess what they are." For instance, if the right ear starts twitching like crazy, it may mean you just spotted a mouse or … well … you do the mind-reading.

Some pluses and minuses of the ears are obvious. You might want your boss to know how closely you're paying attention at a boring business meeting. Then again, you might not. And that's putting aside how impressed said boss might be with the whole cat-ears look.

Speaking of which, in the United States, Necomimi ears are not exactly everyday wear. But they're popular with teenage girls, Yang says, and with anime fans and costume partygoers. In Japan, he says, "people wear them on the street. They're a part of fashion."

You can get covers for the ears in various colors and patterns "to match your outfit," Yang says. The ears, around $70, and covers, $10 to $20, are sold in some comic book stores and toy stores, and soon you'll find them in some national chains. They're also available online, including at http://www.necomimi.com.

"Most people, when they put the ears on and they start moving, they break into a big laugh," Yang says. "And it's even more fun for people watching."

health@latimes.com