GREENFIELD, Mass. —

The first night they slept entwined on his futon, Jack Robison, 19, who had since childhood thought of himself as “not like the other humans,” regarded Kirsten Lindsmith with undisguised tenderness.

She was the only girl to have ever asked questions about his obsessive interests — chemistry, libertarian politics, the small drone aircraft he was building in his kitchen — as though she actually cared to hear his answer. To Jack, who has a form of autism called Asperger’s syndrome, her mind was uncannily like his. She was also, he thought, beautiful.

So far they had only cuddled; Jack, who had dropped out of high school but was acing organic chemistry in continuing education classes, had hopes for something more. Yet when she smiled at him the next morning, her lips seeking his, he turned away.

“I don’t really like kissing,” he said.

Kirsten, 18, a college freshman, drew back. If he knew she was disappointed, he showed no sign.

On that fall day in 2009, Kirsten did not know that someone as intelligent and articulate as Jack might be unable to read the feelings of others, or gauge the impact of his words. And only later would she recognize that her own lifelong troubles — bullying by students, anger from teachers and emotional meltdowns that she felt unable to control — were clues that she, too, occupied a spot on what is known as the autism spectrum.

Only since the mid-1990s have a group of socially impaired young people with otherwise normal intelligence and language development been recognized as the neurological cousins of nonverbal autistic children. Because they have a hard time grasping what another is feeling — a trait sometimes described as “mindblindness” — many assumed those with such autism spectrum disorders were incapable of, or indifferent to, intimate relationships.

Yet as they reach adulthood, the overarching quest of many in this first generation to be identified with Asperger’s syndrome is the same as many of their nonautistic peers: to find someone to love who will love them back.

A meeting

Kirsten was introduced to Jack in the fall of 2008 by her boyfriend at the time, who jumped up from their table at Rao’s Coffee in Amherst, Mass., to greet his friend, who was dressed uncharacteristically in a suit that hung from his lean frame.

Jack, it turned out, was on his way to court. A chemistry whiz, he had spent much of his adolescence teaching himself to make explosives and setting them off in the woods in experiments that he hoped would earn him a patent but that instead led the state police and the Bureau of Alcohol, Tobacco, Firearms and Explosives to charge him with several counts of malicious explosion.

By the following spring, he would be cleared of all the charges and recruited by the director of the undergraduate chemistry program at the University of Massachusetts, who was impressed by a newspaper account of Jack’s home-built laboratory. Kirsten’s boyfriend, a popular Amherst High senior, had offered to serve as a character witness for his former classmate, and the three spent much time together that year.

The boyfriend told Kirsten that Jack had Asperger’s syndrome: His condition may have blinded him to the possibility that the explosions, which he recorded and posted on YouTube, could well be viewed by law enforcement authorities as anything other than the ambitious chemistry experiments he saw them as.

But if Kirsten noticed that Jack held himself stiffly, spoke with an unusual formality and rarely made eye contact, she gave little thought to his condition, other than to note that it ran in families: His father, John Elder Robison, is the author of “Look Me in the Eye,” a best-selling 2007 memoir about his own diagnosis of Asperger’s at age 39.

After reading of the intense interests that often come with the condition — the elder Robison’s passion for Land Rovers, he had written, was the basis for his successful business servicing luxury vehicles — Kirsten and her boyfriend made light: “I have Asperger’s for McDonald’s,” she would joke. But Jack was all too familiar with the book’s more sobering stories, too: about the despair his father felt in his youth as he looked at happy couples around him and his rocky marriage to Jack’s mother, which ended in divorce.

“All these young Aspergians want to know how to succeed at dating,” John Robison told his son after his speaking engagements.

And as a high school girlfriend broke up with Jack over the course of that year, Jack began to wonder more urgently about the same question.

Kirsten’s two previous boyfriends had broken up with her, too, and her current boyfriend was an unlikely match — a charismatic extrovert with soulful blue eyes who thrived on meeting new people. But when she admitted at the outset of their senior year in high school that she envied his social ease, he had embraced the role of social coach.

Years of social rejection had made her, in his view, overly eager to please.

“People will take advantage of you if you act that way,” he warned. “If you don’t watch out, you’ll be a natural doormat.”

Noting her tendency to speak in a monotone, he urged her to be more expressive. He sought to quiet her hand movements, gave her personal hygiene tips (“You can’t do that,” he told her flatly when she used her fingers to scoop up food she had dropped on a table at Taco Bell and ate it) and pointed out the unspoken social cues she often missed. He elbowed her as she spoke for long minutes to an acquaintance about her interest in animal physiology.

“When people look away,” he explained, “it means they’re not interested.”

Diagnosed with attention deficit hyperactivity disorder at age 11, she never heard the word autism. They were convinced that with some effort she could become as socially adept as he was.

But she also chafed at his frequent instructions, which required constant, invisible exertion to obey. And she despaired of ever living up to his most urgent request: that she share her innermost feelings with him.

“Just don’t filter,” he said one night, lying in bed with her.

In contrast to her boyfriend’s emotional probing, Jack’s enthusiasm for facts — like how far his green laser pointer could reach across the University of Massachusetts campus in Amherst — came as a relief. So, too, did his apparent lack of concern for fitting in.

If Jack had trouble reading Kirsten’s expressions and body language, he also noticed that she had what he considered a perfect smile. On his laptop, he showed her bootleg episodes of his favorite TV show, “Breaking Bad,” about a chemistry teacher turned methamphetamine producer. And on the evenings when he argued libertarian positions with Kirsten’s boyfriend, a liberal Democrat, he often found himself disappointed when she went to bed early.

One afternoon in the fall of 2009 he asked if she was free to meet between classes at UMass, where she was enrolled as a freshman and he was studying chemistry for an associate’s degree. They talked about their childhoods in Amherst, both social outcasts even among their geeky classmates, offspring of academics. Jack’s poor grades reflected the hours he spent reading chemistry websites rather than doing homework; one teacher had suggested to Kirsten’s mother, an administrator at UMass, that she would be “a perfect candidate for home schooling.”

Kirsten told Jack, at some length, of her desire to be a medical examiner. He replied, at even greater length, about chemistry, his interest having shifted from explosives to designing new compounds for medical use. Sometimes, as they circled the campus, she broke in with questions.

“What’s that?” she wanted to know when his descriptions grew technical, or “Why?”

Accustomed to being treated with something more akin to polite fascination when he held forth on his favorite subjects — he often felt, he said, like a zoo animal — he checked to be sure her interest was genuine before providing detailed answers.

Their difficulty discerning unspoken cues might have made it harder to know if the attraction was mutual. Kirsten stalked Jack on Facebook, she later told him, but he rarely posted. In one phone conversation, Jack wondered, “Is she flirting with me?” But he could not be sure.

But Jack, who had never known how to hide his feelings, wrote Kirsten an email laying them out. And when Kirsten’s boyfriend pleaded with her to tell him what was wrong, she did, sobbing. She could not explain, she said. She knew only that she felt as if she had found her soul mate.

Road bumps

From the beginning, their physical relationship was governed by the peculiar ways their respective brains processed sensory messages. Like many people with autism, each had uncomfortable sensitivities to types of touch or texture, and they came in different combinations.

Jack recoiled when Kirsten tried to give him a back massage, pushing deeply with her palms.

“Pet me,” he said, showing her, his fingers grazing her skin. But Kirsten, who had always hated the feeling of light touch, shrank from his caress.

“Only deep pressure,” she showed him, hugging herself.

He tried to kiss her, but it was hard for her to enjoy it, so obvious was his aversion. To him, kissing felt like what it was, he told her: mashing your face against someone else’s. Neither did he like the sweaty feeling of hand-holding, a sensation that seemed to dominate all others whenever they tried it.

They found ways to negotiate sex, none of them perfect. They kept trying.

What mattered more to Kirsten was how comfortable she felt for the first time in a relationship. Even if she did something wrong, she believed, Jack would not leave her.

She moved out of her dorm and into his apartment that fall. Despite his distaste for her habit of scavenging, he did not complain when she decorated his bare living room with a plastic orange, magnetic trains and a Wolverine action figure rescued from the sidewalk.

For his part, Jack rejoiced to find that Kirsten did not hold certain social expectations that had caused him anxiety with a high school girlfriend. He apologized, for instance, that he failed to get her a Christmas present because he had not been able to think of what she would like.

“It doesn’t matter,” she said with a shrug. “I can tell you what to get me next time.”

The diagnosis

Looking for clues to fix her new relationship, Kirsten began frequenting autism websites like WrongPlanet.net, where hundreds of messages a day are posted.

“Eligible Odd-Bods,” read one. Another, “Are relationships harder for Aspies?”

In the library, she paged through autism guidebooks, few of which contained any information about relationships, not to mention sex. But as she read about the manifestations of the condition, she recognized them — and not only in Jack.

In one chapter about the repetitive behavior and thought-process “ruts” that are common among autistic people, she saw her own difficulty climbing out of her black moods.

And then there was the characteristic of autism — focusing on a detail rather than the whole — that seemed to define the nitpicky arguments she and Jack had daily, even hourly, it sometimes seemed. There was the one, for example, when they were trying to recount something that had happened at a particular hotel, but could not advance past the semantics of its size.

“The hotel was miles wide,” Kirsten had started. “And …”

“It was not ‘miles’ wide,” Jack had broken in. “It was maybe an acre, but not a mile wide, I can guarantee it.”

These fights, which Jack had dubbed “Aspie arguments,” were not soul-sapping, but the cumulative effect was exhausting. It had been Jack’s similar escalation of arguments with his father that had prompted John Robison to send him to the therapist who gave him the Asperger’s diagnosis at age 15.

No prescription would come with a diagnosis, Kirsten knew. The only drugs for autism treated side effects, like depression or anxiety; she already had medication for ADHD. It might help her get more time for assignments at school, where the constant effort of social interaction sometimes left her drained and struggling even with tasks that should be easy for her. But mostly, she wanted to know if there was an explanation for the awkwardness that had plagued her for so long.

Her answer came in the fall of 2010, the result of a six-hour battery of questionnaires and puzzles and a visit with a psychologist.

“Lack of awareness of self-impact,” the report read. “Diminished expression of ordinary social graces.” She had left, the doctor wrote, “without a parting word.”

Many others with the same diagnosis, she knew, were more impaired than she. In online forums, she encountered skeptics who saw Asperger’s as an excuse for rudeness — or, worse, a means of pathologizing essentially normal behavior and diverting resources from those who were truly challenged.

But Kirsten took heart in the official acknowledgment and the community it made her a part of. She changed her account setting at WrongPlanet.net from “undiagnosed” to “Asperger syndrome” and persuaded her mother to pay for a therapist who specialized in treating people on the autism spectrum.

Therapies

Jack and Kirsten considered autism a part of who they are and fundamental to what drew them to each other.

But for a time this past summer, Jack became captivated by the idea of designing an empathy drug. He read all he could find on the hormone oxytocin, which has been linked to trust and social interaction.

A small study suggesting that some of the social difficulties associated with Asperger’s syndrome could be relieved temporarily by inhaling an oxytocin nasal spray had generated media interest the year before.

But to Jack the more interesting possibility was a drug that worked on the same principle as the popular antidepressants called SSRIs, whose effect could last considerably longer than a spray.

They had both undergone a different experimental treatment, for a study at Harvard Medical School. Jack’s father believed that earlier studies with that procedure, which delivered current to areas of the brain, had given him a temporary insight into other people he had not had previously. But they had noticed no such effect on themselves.

And Kirsten had been working hard with her own therapist to develop strategies for soothing herself. When she found herself in a bad-mood rut, she had agreed with her therapist, she would visualize the nerdy intellectual character in the animated children’s show “My Little Pony” — of which her knowledge bordered on encyclopedic and whose goofiness made her laugh.

Dating advisers

On a day early this month, Kirsten and Jack stood before a group of young adults with autism at the Kinney Center for Autism Education and Support in Philadelphia, answering their questions while Jack’s father addressed their parents in a different room.

“Did you ever think you would be alone?” one teenager wanted to know.

Kirsten answered first.

“I thought I was going to be alone forever,” she said. “Kids who picked on me said I was so ugly I’m going to die alone.”

Her blunt tip on dating success: “A lot of it is how you dress. I found people don’t flirt with me if I wear big man pants and a rainbow sweatshirt.”

Then it was Jack’s turn to answer, in classic Aspie style.

“I think I sort of lucked out,” he said. “I have no doubt if I wasn’t dating Kirsten I would have a very hard time acquiring a girlfriend that was worthwhile.”

A mother who had slipped into the room put up her hand.

“Where do you guys see your relationship going in the future?” she asked. “No pressure.”

Jack said, “I see it going along the way it is for the foreseeable future.”

“So I guess you’re saying, there is hope in the future for longer relationships,” the mother pressed.

Kirsten gazed around the room. A few other adults had crowded in.

“Parents always ask, ‘Who would like to marry my kid? They’re so weird,’” she said. “But, like, another weird person, that’s who.”