Brad Williams, a radio anchor in La Crosse, Wis., enjoys having his memory tested. Williams' ability to recall dates and details from his life is being studied by researchers.

LA CROSSE, Wis. — For as long as he can remember, Brad Williams has been able to recall the most trifling dates and details about his life.

For example, he can tell you it was Aug. 18, 1965, when his family stopped at Red Barn Hamburger during a road trip through Michigan. He was 8 years old at the time. And he had a burger, of course.

"It was a Wednesday," recalled Williams, now 51. "We stayed at a motel that night in Clare, Michigan. It seemed more like a cabin."

To Williams and his family, his ability to recall events — and especially dates — is a regular source of amusement. But according to one expert, Williams' skill might rank his memory among the best in the world. Doctors are now studying him, and a woman with similar talents, hoping to achieve a deeper understanding of memory.

Williams, a radio anchor in La Crosse, seems to enjoy having his memory tested. Name a date from the last 40 years and, after a few moments, he can typically tell you what he did that day and what was in the news.

How about Nov. 7, 1991?

"Let's see," he mused, gazing into the distance for about five seconds. "That would be around when Magic Johnson announced he had HIV. Yes, a Thursday. There was a big snowstorm here the week before."

He went on to identify correctly some 20 other events including the birth of the first test-tube baby in 1978, the toxic-gas leak in Bhopal, India, in 1984, and Billie Jean King's victory over Bobby Riggs in tennis' "Battle of the Sexes" in 1973.

"I've always been this way," Williams said. "Growing up, I never really had reason to think I wasn't like everyone else."

So how does he do it?

"You want the Nobel Prize right now? Tell me that answer and I'll publish it," said Dr. James McGaugh, who has studied Williams since last summer. "We don't know. We do know that he carries this information with him, that it's detailed, that it's just there. That's what we want to know — why is it there?"

Williams' brother first contacted McGaugh, a research professor at the University of California, Irvine, after the neurobiologist published a case study of a similar person in the journal Neurocase in 2006.

That woman is in her mid-40s and was identified only by the initials A.J. She told McGaugh whenever she hears a date, memories from that date in previous years flood her mind like a running movie. The phenomenon, she laments, is "nonstop, uncontrollable and totally exhausting."

"Most have called it a gift, but I call it a burden," she wrote. "I run my entire life through my head every day and it drives me crazy!!!"

McGaugh and his colleagues subjected A.J. to a battery of psychological tests. Given a date at random, she was nearly flawless in recalling the day of the week and what she did that day. The details she provided invariably matched what she had written in diaries decades earlier.

The number of people with comparable memory skills has been hard to pin down. After publishing his research with A.J., McGaugh heard from about 50 people claiming they had the same skill or, like Williams' brother, knew someone who might.

Of them, McGaugh and his colleagues have identified a third person — a 50-year-old Ohio man — who shows similar promise.

Ever since pointing his elder brother in McGaugh's direction, Eric Williams, 45, has been recording Brad's adventures for an upcoming documentary. The movie, to be titled "Unforgettable," is scheduled to be completed later this year.