I sit in a tiny exam room at Columbia University. Underneath my shirt, EKG electrodes tug gently on my skin, one stuck to each shoulder blade and one on my belly. Similar electrodes adhere to my 9-year-old daughter Ava, sitting beside me. As we silently read National Geographic Kids and Highlights magazines, a line tracking our heartbeats rolls across the nearby computer screen for scientists to review later. This is our spring-break activity: having our parent-child bond evaluated by a functional magnetic resonance imaging (fMRI) study and a battery of psychological and physiological tests.

Columbia professor Nim Tottenham had suggested we try it when I asked to observe Columbia’s Developmental Affective Neuroscience Lab ahead of a book I was writing about the roots of “bad behavior” in children today. I was specifically interested in Tottenham’s research on how children learn emotions from parents and how mothers’ physiology affects their children’s heartbeat and stress levels. Ultimately, her team was seeking a scientific answer to the question: What makes a good parent?

I’d been inspired to write the book after noticing an apparent increase in attention and mood problems among my own children’s peer group. In my research, I’d begun to see that an increase in tantruming toddlers, kicking kindergarteners, and mouthy middle schoolers represents a fundamental shift in the way children grow up nowadays. This apparent bad behavior often stems from an underlying problem with self-regulation, whether an attention disorder (poor impulse control and focus), anxiety (resistance to transitions or activities that spark fear), or depression (refusing to engage in school or chores). A stunning one in two children will develop a mood or behavioral disorder, or substance addiction, by age 18, according to the National Institute of Mental Health. Even children who don’t have a diagnosis show less cooperation with other kids or adults than in previous generations, according to hundreds of conversations I’ve had with parents, educators, and scientists.

This is a generation of children and young people struggling to manage their emotions, thoughts, and behavior. They’re desperate for support from the adults around them. Now more than ever, the question of good parenting is critical.

The day at Columbia began with us filling out paperwork in the lab, whose rooms looked like a nondescript doctor’s office. Ava leaned forward in a low armchair, listening to the explanation of the day ahead. She wore a baggy T-shirt and sweats, her long brown hair pulled into her typical messy ponytail. My 12-year-old son, James, stood nearby, snapping photos and watching.

“In this lab, we’re very interested in emotion and brain development,” explained Bridget Callaghan, a postdoctoral scholar with a perky Australian accent. “We’re really interested in how kids learn about particular things, how they respond emotionally, and also how their parents help them to change how they think and feel.”

This first day, Ava and I would be playing computer games and taking psychological, language, and math assessments, often while our heartbeats, sweat production, and hormone levels were being measured. The next day we’d go to Columbia’s medical center for mother-daughter fMRI scans, Callaghan explained.

“Have you ever been in an MRI machine before?” she asked Ava.

“I’ve seen pictures of one,” she responded.

“An MRI machine is pretty cool,” Callaghan said. “It uses magnets, which turn on and off really quickly, to take photographs of your brain. It’s very special because it’s able to see beneath your skin to show you what your brain looks like.”

Lab manager Kaitlin O’Sullivan gave Ava a piece of gum and asked her to chew it until it was “juicy” and her mouth filled with enough spit to be soaked up by a wad of cotton. That would give a baseline measurement of Ava’s cortisol level, an approximate measure of stress, to compare to another spit test in 90 minutes.

Next, we answered a battery of questions to screen for metal that might be in our bodies, which could be dislodged by the powerful magnets in the MRI machine. Ava had never worked as a machinist. She had no cochlear implants, shrapnel, or bullets in her body. Callaghan reassured Ava that nothing painful would happen to her.

“You’re volunteering your time, and we’re really happy you are,” she said. “It’s really important that if you feel uncomfortable or there’s anything you feel you can’t do, just let us know.”

Callaghan took a photo of me that would be shown to Ava later in the study. Then, they hooked us up to EKG electrodes and left us for the quiet time alone together, during which they expected our heart rates and breathing to synchronize. I felt very aware of the wires enmeshing me and didn’t want to move my body or disturb the web of cords. Ava, on the other hand, seemed perfectly comfortable and relaxed. She came across some knock-knock jokes — her favorite. She read them to me, just as if we were sitting on the couch at home. After a few minutes, Callaghan returned to unhook us.

Then we separated. Callaghan hooked me up to new wires to measure my sweat response, while O’Sullivan took Ava to perform computerized tests in another room. I sat in front of a computer with earphones on so that I could hear an annoying sound playing periodically while I watched different-colored shapes appear on the computer screen. A camera videotaped my reaction — a scrunched-up face and slight startle when I heard the noise — to play back for Ava while she was inside the fMRI machine. The goal: to see if she could learn about threats more effectively from watching her mother’s — rather than a stranger’s — experience.

Once I completed the annoying noise video, Callaghan turned off the video camera and gave me a final task on the computer. As pictures of animals flashed across the screens, either scary or cute, I realized that I was taking the implicit bias test, which I’d taken before, when I was writing about unconscious racial bias. Then, she set me to work filling out a long questionnaire about my child-rearing practices, demographics, general health, and Ava’s health and development, as well as psychological assessments to evaluate Ava for anxiety, grit, depression, and behavioral disorders. I felt relief and a powerful sense of accomplishment: I’d penetrated a psychology study. Finally, I could witness the inner workings.

In 1973, a Columbia psychiatrist named Myron Hofer made a crucial discovery about mothers and children purely by accident. After arriving at his lab one day to find that a mother rat had chewed through her cage and escaped, he observed her rat pups were shivering in the nest, their body temperatures having dropped to less than half of normal while they were unable to snuggle next to her warm body. Thinking that the pups simply needed to be warmed, Hofer tried doing so with a man-made heat source — but the pups still showed sluggish heart rates. He tried stimulating the babies with a cloth that smelled like their mother, and he tried grooming them; each of these efforts helped, but the pups’ overall metabolic activity remained subdued.

Hofer’s research led to a whole body of work on early infant separation in humans and mice and helped support developments in attachment theory that traced emotional and behavioral problems in adulthood back to infancy. This launched the era of attachment parenting, defined by William Sears’s The Baby Book, published in 1993. Research on the importance of early childhood development and secure attachment for lifetime success reinforced the importance of nurturing parents and set the stage for a cascade of writings on mommy guilt. Whereas 1950s homemakers thought nothing of leaving Junior in a playpen for hours while they completed their daily chores, moms in the 1990s and early 2000s co-slept, wore their babies, and often had no privacy from their children, not even in the bathroom. (I plead guilty on the latter two.)

Scientists can look at the brains of young mammals — whether humans, rats, or monkeys — when they’re separated from their mothers and see reactivity in the amygdala, which controls the fight-or-flight response. When the mom comes back, researchers have observed, the children’s brains return to normal. In further experiments in the 1970s, Hofer showed that rat pups’ fear response could be switched on by the mom’s behavior — remarkably, pups responded even when scientists piped the scent from their fearful rat mother into the cage. In a similar fashion, human babies look to their mothers for cues as to whether a new situation or object is safe. This is one reason, researchers believe, that conditions such as anxiety, depression, and other mood disorders are so often passed down from parent to child, not just genetically but owing to environmental factors as well. When a parent can’t effectively regulate their own emotions or their sense of fear, children don’t learn to do so.

Although behavioral scientists have observed the intergenerational transmission of mental illness, researchers like Columbia’s Tottenham are just beginning to understand the biological mechanisms that underpin mental health and dysregulation. The key is to figure out the impact of visible parent-child interactions on the cellular changes that require microscopes and MRI machines to document.

After the scientists finished with me in the lab, I regrouped with Tottenham to talk about how her interest in biology, emotional development, and parent-child relationships had come together over time. She was chic in black pants, tank top, and shirt, a trim woman with a neat, dark chignon and the energy of someone whose to-do list exceeds the time in the day. As we talked, she periodically glanced at the time on her Fitbit to be sure she wasn’t late for her next appointment. Like me, Tottenham has an Asian mother (Korean) and a white father (Irish-English).

“Studying children who have an extreme disruption in caregiving makes it clear that parents are important,” she explained. Her inflection was low and controlled, the habit of a petite woman determined to be heard and taken seriously.

“We certainly knew that from decades of work, but we don’t know why parents are important. What are parents actually doing on a moment-to-moment basis to sculpt our emotional biology? We have these micro-interactions with our kids all day long — that’s really what parenting is — so what effect does that have in childhood?”

Every test that my daughter and I took would help the lab get at a different question: Could Ava learn to avoid a shape that triggers an annoying noise from watching my emotional reaction? Would she learn faster watching me as compared to a stranger? When we sat together, how quickly did our heartbeats and breathing synchronize? If I was in the room, did she perform better on a computerized task?

“From a neuroscientific vantage point, you want to get to the level of mechanism: if you pull this lever, what happens?” Tottenham said. “The parent’s presence is a powerful buffering effect against a lot of arousal in the emotional brain region.”

The results of all the experiments that Ava and I participated in would help the lab piece together a picture of how a parent’s influence and simple physical presence can help children learn and self-regulate. Eventually scientists will understand how parents can protect children from threats at the neural level, as well as how parents unwittingly pass along anxiety, depression, and other pathologies to their offspring. Unfortunately, Ava and I wouldn’t get our individual results — all the study participants would remain anonymous and be lumped together.

As Tottenham and I finished up our chat, she asked about a casual comment my son had made while I was filling out paperwork. It turned out that one of the many questions I answered — to which James knew the answer — disqualified me and Ava from participating in the fMRI study the following day. Since I started my book reporting in 2012, I’d wanted to observe an MRI study; the findings were central to so much of the research I was reading. Stunned into silence, we gathered our belongings and walked out into the humid spring day.

On the sidewalk, I wheeled upon James with a harsh reprimand. Why was he chattering about our personal business? Ava stood there mutely, disappointed that she wouldn’t get to experience the MRI machine. James took off in a huff, dashing down the busy New York City sidewalk.

In a few seconds, the lunchtime crowd engulfed him. I grabbed Ava’s hand and hurried after him.

My years of book research drummed one fact into my head: the parent-child connection is critical to healthy development. Separation and other childhood experiences sculpt the brain in ways that can stay with a person for life. For instance, children raised in orphanages often exhibit lasting brain changes because, even though their physical needs are met, they’re unable to form a secure emotional attachment to a caregiver and they endure chronic stress. Studies of the brains of children raised in Romanian orphanages with ten-to-one infant-adult ratios found abnormalities in the prefrontal cortex and amygdala. As a result, the children were more impulsive and had deficits in attention and intellect.

Does this mean that experiencing any stress at all is bad for children?

Not at all. It’s important for babies and young children to learn to tolerate moderate amounts of stress, and then to experience relief. When infants cry to be fed and are nursed by a responsive mother, their brains release a flood of endorphins into their nervous systems. These are the “feel-good” hormones we experience after exercise. This arousal-relief cycle actually helps tone infants’ brains by developing self-regulatory neural patterns and building trust that their needs will be met.

Similarly, when children separate from their parents to go to preschool, they may be upset and cry. If comforted by loving caregivers — and reunited with the parents later, as promised — they learn confidence and are better protected from developing anxiety in the future. Repeated separation or feelings of anxiety, followed by reassurance and calming, is actually protective. That process is like a workout for the brain; it creates neural pathways that help you manage stress and anxiety. Children who never face stress are more likely to respond with anxiety or overreaction because it’s so unfamiliar.

Our children pick up on our strategies for managing strong emotions and difficult situations. This hit me hard one day after school. My intense older child James announced: “I’ve had a very stressful day. I can’t handle this right now!” The chaos of snack and jostling with an energetic younger sister had pushed him over the edge.

But in his irritated voice, I heard an exact copy of my tone and the words that I would use with them. If they were too noisy, or I hadn’t gotten enough sleep, I would feel on edge and jittery and dysregulated. But rather than taking responsibility for bringing myself back under control, I would blame the circumstance or — worse — blame my own children. I had to learn to own whatever moods and feelings washed over me and to model self-regulation if my kids were going to learn to do the same. I realized that in deciding to become a parent, I had lost the luxury of reacting with immature outrage when my feelings or pride get hurt. From then on, I made an effort to say things like, “I’m feeling stressed. I need to take a five-minute walk to calm down.”

Every parent has different baggage. For me, perfection and rigidity were holding me back. Maybe you’re one of the many parents managing an anxiety or mood disorder. In their lifetime, about 29 percent of American adults experience an anxiety disorder, 25 percent deal with an impulse control disorder, 21 percent have a mood disorder, and 15 percent abuse substances, according to government data.

Clutching Ava’s hand, I speed-walked to catch up with James. We dodged a hipster college student in line for the food truck. James’s dark mop of hair came into view.

I grabbed his shoulder. From my review of Tottenham’s research, I knew that kids copy our autonomic physiological systems as well as our body language and the words we say. I forced myself to take a deep breath and speak in a calm voice. I needed to restore our parent-child connection, the linchpin to mental health.

“James, let’s get some food,” I said. “We’ll all feel better after lunch.”

“I’m not hungry,” he snapped at me. He pulled his body out of reach.

“Look, there’s a Chinese dumpling food truck,” I said, relieved that he’d stopped running.

Anger had sometimes sent James stalking away from the family, out of sight even on unfamiliar city streets. Now he stood a safe distance away from me, face knotted in a scowl.

Ava and I ordered three different kinds of dumplings and noodles. We perched on a nearby bench. Ava devoured the food. I picked at the cheap, doughy noodles. James sat with us, but spurned the food. I urged him to eat. I didn’t need a scientist to evaluate my connection to James right then. Any of the random passersby looking at his rigid back and clamped-shut mouth could have seen that it was strained.

Looking at his stiff back, I knew we had to reconnect. I didn’t have time to wait for the results of Tottenham’s research. Maybe a gentle touch would help him calm down.

“James, it’s okay,” I said. I put an arm around his shoulder. He let it rest.

“It’s not okay,” he shouted. “I ruined your book! I’m always messing up.”

“You didn’t ruin the book. I’ll find a way to write around it. Or I’ll find another lab that will let me observe. The important part is describing the research,” I said. “I was wrong to blame you. Once they read through all my answers on the questionnaires, they would’ve called to tell us not to come tomorrow. We wouldn’t have been able to participate. This actually helped us plan to have a fun day tomorrow.”

He turned to face me. Lip thrust out. Eyes wet.

“Why don’t you have something to eat?” I said.

“This food is disgusting,” he said. But he picked up a fork. He chose a noodle from the corner of the white Styrofoam container, without any meat sauce on it. Slurped it into his mouth.

“I really appreciated your help,” I said. “You took pictures for me in case the photographer’s don’t come out. You were so patient during the boring sections when Ava and I were both occupied.”

He wasn’t smiling. But at least he swallowed another noodle. And then another. “What should we do now? Do you want to go back to Uncle Chris’s apartment and build some Legos?”

Both kids agreed. I wrapped up the remains of the Chinese food and grasped my son’s hand.

We walked to the subway entrance. Together.

The day hadn’t gone as I expected. Instead of merely observing science in action, I’d seen the importance of the parent-child relationship play out in my own family. When I lost my temper and lashed out, my child responded by fleeing. It took a gentle touch and apology (and some food) to restore that connection and help James bring his amygdala back under control. Thinking of the electrodes surrounding me and Ava as we sat together in the lab, I resolved to focus more on my own reactions to conflict, to calm my own body before trying to soothe a child’s upset.

Am I a good mom? I wouldn’t get an answer to that question from Nim Tottenham today. But no matter what a scientific test would’ve shown me or what the researchers could’ve observed from an MRI scan, I was pretty sure I already had some idea.

Katherine Reynolds Lewis is a Washington, D.C.–area journalist, author, and mother of three. This is an adapted excerpt from The Good News About Bad Behavior: Why Kids Are Less Disciplined Than Ever – And What to Do About It by Katherine Reynolds Lewis. Copyright © 2018. Available from PublicAffairs, an imprint of Perseus Books, LLC, a subsidiary of Hachette Book Group, Inc.