In Avatar, the giant blue Na’vi are animated by human actors wearing reflectors tracked by computers. This is what gave Sam Worthington’s and Sigourney Weaver’s avatars such lifelike grins, grimaces and frowns.

Recently, in Walnut Grove, California, I donned high-tech reflectors, too, though not as a movie star. I was being tested on a novel device that uses Hollywood tech to see if I have Attention Deficit Hyperactivity Disorder.

Beams of light are flashed to the reflectors and bounced back to sensors so sophisticated they can detect minute movements - including telltale motions associated with ADHD behavior–if, for example, I move my legs or head just 0.4 millimeters. Motions are recorded 50 times per second during a 20-minute computer test used by physicians to diagnose and measure ADHD.

The test requires a subject to tap a key on a keyboard when stars shapes appear on a screen, except when the star has four points. It’s an intentionally boring exercise that nonetheless requires one to pay attention–and to stay still.

“This device provides a very good objective measurement of whether a patient has normal pattern of movement and distraction, or one associated with ADHD,” says Calvin Sumner, a psychiatrist and the Chief Medical Officer of BioBehavioral Diagnostics, which makes the Avatar-like device called the Quotient ADHD System.

The Quotient system has tested 46,000 patients, and helps clinicians make what can be a difficult ADHD diagnosis for some patients. “It’s become an important part of how I assess patients,” says Akindele Kolade, the psychiatrist and BioBehavioral customer who would be running my test. Kolade has one of the $19,500 devices, which come with a computer, keyboard, and Avatar-getup mounted in a gray plastic cubicle.

When I took the test, I was nervous. Like many people who think they are master multitaskers, I secretly feared that my tendency (compulsion?) to simultaneously talk on the phone, scan emails, and check baseball scores is actually ADHD.

Once strapped in, I attempted to sit as still as the Buddha and got annoyed when I made a few errors. But the 20 minutes went by surprisingly fast, even though I couldn’t tell you the last time I sat still doing something that boring for a full 20 minutes.

When I finished, my test was sent to the BioBehavioral head office and run through an algorithm, with the result appearing back in Kolade’s office almost immediately.

“You are normal,” said Kolade, to my relief.

I had strayed a few times into the “distracted” category, he said, which showed up “red” on the printed timeline of my test. But I was able to return to the “green” level of attentiveness. “People with ADHD struggle to return to attentiveness once they are distracted,” said Sumnar. “We have run enough tests and collected enough data to see this pattern very clearly.”

I was relieved to be designated “normal”, although as I returned to my office and reengaged with iPhone, computer, and several other tasks more or less simultaneously, I wondered.