The discovery five years ago culminated this spring with Kodak donating seven patents to a Massachusetts research hospital in hopes of developing a new tool for identifying the neurobehavioral disorder that afflicts millions of Americans.

"The diagnosis of ADHD is highly subjective — there's no definitive test you can give someone that says they've got it or they don't," said Greg Foust, a research manager in Kodak's System Concepts Center. "What this technology allowed us to do was not only definitively and objectively determine if someone had it but also get a sense of the degree of the affliction."

Kodak scientists spied the unusual temperature oscillations in one of 72 volunteers in a 1998 study. The researchers were just starting to examine whether images, sounds and other distractions are useful in reducing stress levels or even treating psychiatric ailments such as depression.

Each volunteer, wearing headphones to block out sounds, was placed in an empty room or in front of a blank computer or television for 10 minutes and had temperature sensors attached to their pinky fingers.

Deprived of visual and audio stimulation, ADHD sufferers typically become stressed as they look for an outlet, Foust said. That stress drives changes in fingertip temperatures that appear to fluctuate differently from non-ADHD patients, he said.

"The way their temperature changed was very erratic," Foust said. "It would tend to decline or rise in a manner that was very bouncy versus, in non-ADHD persons, the temperature change was very slow without a lot of oscillation."

Two other people who displayed "jagged changes" in temperature readings also were found to be stricken with ADHD.

The disorder affects as many as 10 million adults in the United States and between 4% and 12% of school-age children — as many as 3.8 million youngsters. Its symptoms include short attention span, impulsive behavior, difficulty focusing and sitting still.

Kodak did a follow-up trial in 2000 on 32 children — half of them diagnosed by doctors with ADHD — and found its method to be at least 84% accurate in spotting the disorder. The current diagnosis process is largely subjective because patients must be observed over long periods of time, often in both home and school settings.

In exchange for an $8 million tax benefit in this year's first quarter, Kodak turned over its patented procedures to McLean Hospital in Belmont, Mass., a pioneer in ADHD research affiliated with Harvard Medical School. Kodak spokesman Anthony Sanzio said the hospital is much better suited to advance the research.

If the technology leads to a commercial product, the hospital will reap all the revenues.

"These inventions could help lay the foundation for improving the speed and accuracy of ADHD tests," said Dr. Martin Teicher, who runs the hospital's development biopsychiatry research program.

Experts not affiliated with Kodak or McLean cautioned that much more research is needed. Dr. Mark Wolraich, professor of pediatrics at the University of Oklahoma Health Sciences Center, questioned how well the temperature process can distinguish "those with an anxiety disorder from those with ADHD."

Teicher said he doesn't think the Kodak method "should be construed as a stand-alone test. It just adds some science to something that tends to be right now very much an art."

Kodak, the world's biggest photography company, is still testing whether images can help alleviate psychological problems. But the results of its work remain under wraps.