My son Ezra was 4 or 5 when he began asking people their birthdays. At first it seemed like a typical child’s question. But then months later he would encounter acquaintances — or even whole families — and reel off the birth months with perfect recall as he pointed at each person.

“Steve, April. Janice, November. Shayna, August.”

Driving him to school one morning, I heard him in the back seat reciting what at first sounded like random dates and names. Then I realized what he was doing: listing the months in calendar order, each followed by the names of everyone he had encountered whose birthday fell in that month.

It was an early glimpse of what I came to realize was an extraordinary — even superhuman — memory. Ezra, now 15, has high-functioning autism. Experts will tell you that the disorder’s most significant characteristic is difficulty communicating and forming relationships. Ezra knows he has autism, but to him one of its primary characteristics is that he can remember things better than most people.

Of course, autism is a spectrum disorder; not every person with the condition has an uncanny memory. Researchers aren’t certain what proportion of people with autism possess powerful recall, nor can they pinpoint exactly what about the brain wiring of people such as Ezra gives them this ability. But many, like Ezra, display remarkable recall that can leave mere mortals floored.

“We don’t know why this is or exactly what brain differences are associated with these traits,” says Susan Bookheimer, a UCLA autism researcher, who says individuals with autism often excel at rote learning while suffering deficits in mastering more fluid areas, such as negotiating social situations.

Flashes of brilliance

My wife and I began noticing this capacity not long after we first realized that Ezra had challenges. Though he seemed to occupy a world of his own — avoiding eye contact, rarely conversing and almost never playing with other children — he would occasionally show flashes of a brilliant mind.

He was 6 when he pointed out the numbers above the door of a house as our minivan drove past. My wife explained that was called an address.

“Bubbe has numbers on her gray house,” he said of his grandmother, who lived in another city. “Bubbe has 2, 7, 6 and 4.”

He was correct.

He went on, flawlessly ticking off the addresses of several of our neighbors, a relative’s Oregon vacation house, even the digits he had noticed above the door of the kids’ gym he visited once a week. What made his recall even more stunning to us was that it so contrasted with his outward appearance: spacey, aloof, lost in his own thoughts.

“How do you remember that stuff?” I asked.

His answer: “I just know.”

In fact, he knew far more.

In second grade, he became fixated on the release date of an animated movie.

“ ‘Shrek 2’ is coming May 19,” he reminded us morning, noon and night. He’d learned the date from preview trailers at the theater and billboards dotting the boulevards of our Los Angeles neighborhood. Once he took in such trivia, it seemed impossible for him to forget it. In time, he built a calendar in his mind, matching movies such as “Home on the Range” and “Shark Tale” with their release dates.

Inspecting the pantry

In school, Ezra struggled to recall the contents of a paragraph in his social studies textbook, and he seemed hard-pressed to tell us what he was learning in science. But on what autism specialists call “preferred topics”— his were animation, animals and breakfast cereals — he routinely surprised us.

Visiting a neighbor’s house, he could hardly stand still for a chat. Instead, Ezra would pry open the kitchen pantry, not to forage for snacks but rather to examine the inventory. Then months or even years later, he’d spot the neighbor at Walgreen’s.

“Hi, Bonnie!” he’d say. “You had Post Honeycombs in your kitchen in August of 2004!”

He was nearly 10 when a relative who knew of his passion for animation gave him a desktop calendar featuring a different Disney movie for each day. I didn’t realize that he had even looked at it much until nearly a year later, when I noticed an orderly stack of the loose pages on a shelf in his bedroom.

“Don’t touch those!” he said.

“I just want to look for a second,” I told him, flipping through and spotting a movie I liked.

“ ‘Finding Nemo,’ ” I said, smiling.

“ ‘Finding Nemo,’ released May 30th, 2003,” he said.

Astonished, I picked up another page.

“ ‘Lion King.’ ”

“June 24th, 1994,” Ezra said quickly.

I looked at the stack, hundreds of pages, and wondered how many he could know. I randomly grabbed another page, this time reading the date.

“What’s on December 15th?” I asked.

“ ‘The Emperor’s New Groove,’ released December 15th, 2000.” Before I could flip to another page, he spoke up again. “There’s a picture of Kuzco, the main character.”

I called my wife into the room, and together we quizzed him on page after page, a couple of dozen in all. He knew them all.

The moment left me astounded — and mystified. When had Ezra ingested all of this information? Had stayed up late at night, studying the calendar under his covers? Or was it a more effortless process? Could he simply snap mental photographs of the pages?

When I tried asking, the most he could tell me was this: “I just see it.”

Feeling more secure

More mysterious than how he did it was why. I knew that autism came with heightened anxiety. What made Ezra most uncomfortable was the unknown: not knowing exactly what would happen next — the next meal, the next vacation, the next movie. Committing concrete things to memory seemed to help to make him feel more secure, more grounded.

But then there was this question: If Ezra could memorize the contents of some 300 calendar pages, then why couldn’t he recall the names of the seven children in his fourth-grade class, children he barely seemed to notice. When asked, he would say one or two names as if he was guessing — “Rachel? Charlie?”— and then beg to be released from the arduous mental task.

I contemplated the impossibly thin line between ability and disability. The very condition that made it so difficult for Ezra to forge friendships — the same wiring that forced him into endless verbal loops and made him uncomfortable in his own skin — made possible these remarkable feats of memory. He found it painfully difficult to do ordinary things such as make eye contact, yet he could effortlessly do what seemed impossible to almost everyone else.

The real question was: Did his memory need to make him solitary and isolated, or could it help him to connect with people?

‘He just knows’

He answered that question at a large family party when he was 12. His usual habit at such events, which could overwhelm his senses with noise and activity, was to flee and hide in a quiet corner or in the lobby. If people tried to interact with him, he wouldn’t notice, or he would fix his gaze on a picture book to avoid interacting.

This time, though, he surprised me by taking interest in the other guests, asking a cousin or a great-aunt, “What’s your name again?” His second question was always the same: “When’s your birthday?”

It was the same thing he’d asked so often as a little boy. But now when he got the answer, instead of just filing it in his mental index, he responded with a movie title: “June 19th? A movie that came out on your birthday was ‘Mulan.’ June 19th, 1998.”

I watched him do this again and again, sometimes reeling off his data so quickly that the person he was quizzing couldn’t understand: “November 13th? Movie-came-out-on-your-birthday-was ‘Beauty and the Beast,’ November 19th, 1991.”

Then he sashayed off to the next guest, leaving the person surprised and puzzled.

“How does he do that?” they’d ask.

I shrugged and offered the only only explanation I had: “He just knows.”

Now in 10th grade, Ezra likes to share what he knows. Still struggling in many realms — such as social interactions and focus in the classroom — he attends a special high school for children with autism and related challenges. He is far more connected to his classmates than he once was, and he reaches out much more, though rarely in typical ways. Ezra counts among his friends a couple of classmates with whom his encounters consist mostly of exchanging trivia about “The Simpsons” and Pixar movies. A dog lover, he commits dog encyclopedias to memory and likes to stop people with unusual breeds at the local dog park to lecture them about their pets.

He is also increasingly self-aware, understanding that the wiring of his brain makes him different from others, but no worse. Ezra still makes a habit of asking new acquaintances their birthdays and identifying a movie that came out that day. When they look at him, wide-eyed and delighted, he always points to his head. “Yeah!” he says with glee, “I have a very good memory!”

Fields-Meyer is a Los Angeles author and journalist. This essay is adapted from his new memoir, “Following Ezra: What One Father Learned About Gumby, Otters, Autism, and Love From His Extraordinary Son” (New American Library).