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Humans are social creatures, and long ago, our survival even depended on our ability to build relationships— otherwise, you’d probably get eaten by a leopard or something. Today, strong, healthy relationships are still important, because they offer us security and comfort.

And they’re especially important in childhood. A lot of the research about how babies form relationships revolves around an idea called attachment theory, which describes how infants relate to their parents or caregivers. Today, we know that your experiences during infancy might even shape how you form significant relationships for the rest of your life.

But how that works, and whether or not you have any control over it, isn’t always as straightforward. Shortly after birth, infants seem to start getting attached to their primary caregivers—usually, their parents. Psychologists define attachment as the deep, emotional bond that makes you want to be with another person.

It’s why you miss someone when they’re gone. The modern idea of attachment theory comes from research conducted by psychologists John Bowlby and Mary Ainsworth starting in the late 1950s. It was based on the idea that kids go through various stages of developing attachment, and that forming a secure bond with at least one main caregiver is really important for a child’s social and emotional development.

First, Bowlby estimated that there are roughly four stages of attachment, which change as a baby gets older. In early infancy—when they’re less than two months old— babies are in a pre-attachment stage. He believed infants that young couldn’t recognize or understand the difference between a stranger and a parent.

Research since then shows that was probably wrong— newborns can recognize their parents— so it might be better to lump them into Bowlby’s second category: the attachment-in-the-making stage, where babies know who their caregivers are but are fine being around strangers. This lasts until about babies are about six months old, when they develop clear-cut attachment. At this stage, they start showing separation anxiety by crying and protesting when separated from their parents.

So if your friend hands you their baby and they start screaming, it doesn’t necessarily mean you’re bad with kids. Finally, when infants get to be about two years old, they start to understand that their caregivers have a schedule and their own lives, and separation anxiety goes down. After that, kids develop more independence and tend to be a little more relaxed when separated from their parents.

But attachment theory isn’t just about the stages of attachment:. It’s also about the kinds of attachments children make, usually during their first year of life, and how those relationships can affect kids down the road. To study this, Ainsworth developed a procedure she called the Strange Situation—essentially, a series of interactions that involved an infant, their parent, and a stranger.

Since it was the 1960s and most people still expected the moms to do the childrearing, almost all of this research was done using mothers and their babies. But some recent studies have shown that other parent-child relationships seem to work in similar ways. There were three phases of the Strange Situation.

First, the mom and baby would be left alone to provide a baseline for their interactions. Then, the researchers would see how the baby reacted if a female stranger entered the room— and what the baby would do if they were left either completely alone or left alone with the stranger. After observing this test with more than 100 infants across four different studies, Ainsworth and her colleagues noticed and described four distinct styles of attachment.

The most common kind—and arguably most healthy—is secure attachment. In the Strange Situation, secure babies are comfortable exploring and moving away from their parents, but might get upset if they’re left alone. Then, they’re quickly comforted when their parent returns.

Resistant attachment is more intense. Babies stay close to their parents, and then get extremely upset if they leave, sometimes reacting with anger when the parent returns. When a baby doesn’t seem to care whether or not there’s a parent or a stranger in the room, that’s known as avoidant attachment.

And if a baby isn’t very responsive or seems depressed, but shows some bursts of intense emotion, it’s called disorganized attachment, which is the kind that’s been most associated with behavioral issues later in life. Even though there are four categories, in recent studies, attachment styles aren’t sharply defined that way— you could kind of consider them on a spectrum from secure to insecure based on certain behaviors. Building off Ainsworth’s studies, scientists have described a couple of dimensions of attachment, which together can show how secure a child is on a sliding scale.

One dimension is proximity-seeking versus avoidant, which basically means how much a baby wants to be near their caregiver. The other is angry and resistant strategies, which describes how angry a baby gets at a caregiver for leaving them alone. If the parent-child relationship is solid and the baby really wants to be around their parent but doesn’t freak out too much if left alone, that generally indicates secure attachment.

But if a baby ignores their parent, or treats them with anger, that’s usually a sign of insecure attachment. But it’s not really clear if using sliding scales instead of categories is that useful or necessary. What’s most important is observing the way a parent treats their child and how the child reacts to that.

No matter how you classify it, that’s what seems to predict later behavior. And attachment styles can be affected by all kinds of things, or a combination of them. It’s specifically thought that parenting has a strong influence, but a baby’s attachment can be influenced by nearly anything that changes how much access they have to their caregiver during their first year of life.

In most cases, stable, affectionate parenting leads to secure attachment, while things that can negatively affect parenting— like abuse, neglect, or even poverty—can cause insecure attachment. If a parent is able to spend a lot of time with their baby— playing with and talking to them, and making sure they always have a clean diaper and a warm bottle— that’s more likely to lead to a securely attached baby. But if, say, a single parent works long hours and can’t spend a lot of time with their baby, or if a caregiver neglects the child, a baby could end up insecure, because they subconsciously feel like they can’t depend on their parent.

Attachment style could also be influenced by something like a childhood illness, when a baby has to spend a long time alone in a hospital and doesn’t get enough interaction with their parents. And this is more than just a bunch of fancy psychology labels. Attachment styles have been shown to impact children as they get older, too.

Many studies about this come from a huge database that tracked over 1000 children and their families from infancy into high school in the 90s and 2000s. It measured how child care experiences related to overall growth and development in childhood, and the data has been used for over 600 studies. For example, researchers found that having a secure attachment in infancy was a good predictor for whether or not kids would be good at self-regulation in preschool— that is, if they could manage their emotions in stable and socially acceptable ways, like not pelting other kids with LEGO bricks.

Meanwhile, having insecure attachments as a baby made older kids more likely to have behavioral problems, like fearfulness and social withdrawal, or bullying and vandalism. And some studies have found that when mothers aren’t attentive to their infants, it can lead to disorganized attachment. In middle childhood and adolescence, these kids are more likely to develop controlling relationships with their parents, where they attempt to direct their behavior— almost like they’re confused about who’s the parent and who’s the kid.

And other research has also shown what seems to be a link between insecure attachment styles and mood disorders, like depression and anxiety, later in life. In most cases, attachment problems don’t come with a clinical diagnosis, but if a child seems especially unresponsive and seems sad, afraid, or reserved, they might be diagnosed with reactive attachment disorder. This is a rare condition that almost only happens in really severe cases, like in abusive families where the child can’t establish a healthy relationship with their caregiver.

And if it’s not treated, it can lead to kids becoming abusive and lacking empathy. Still, it’s not all or nothing. Having a certain attachment style as an infant doesn’t mean you’re destined to show certain behaviors or traits as you get older.

People and circumstances can change. In general, babies who feel they can’t depend on their caregivers are more likely to suffer from other issues later in life— but it’s not a guarantee. And today, thanks to the research done by Bowlby and Ainsworth, there’s also a whole field of study focused specifically on adult attachment, along with how it relates to infancy.

Specifically, adult attachment focuses on the relationships between adults and their friends and romantic partners. There are even surveys to determine what someone’s adult attachment style might be, like the Adult Attachment Scale, which was developed by two psychologists in 1990. It asks questions about someone’s level of trust and intimacy in relationships, like how easy it is for them to feel close to others.

And like recent views of infant attachment, it’s measured from secure to insecure. Just like secure attachments seem to be best for infants, evidence suggests that the traits ranked most desirable in a romantic partner are associated with secure attachment behaviors— like warmth and sensitivity. And overall, adults that test as secure tend to be happier in relationships than insecure adults.

Now, according to some studies, there is a modest relationship between childhood and adult attachment. In a longitudinal study published in journal Child Development in 2000, about 70% of the 50 participants had the same attachment style 20 years after infancy. But if they had experienced a serious negative life event, like losing a parent, a divorce in the family, serious illness, or abuse, their adult attachment style was more insecure.

On the flip side, another study tracking more than 150 young women in 1997, which was published the Journal of Personality and Social Psychology, found that some of the participants actually got more secure as they got older. The researchers concluded that it likely had to do with their changing ideas about relationships, trust, and stability. So under stable family conditions, and without life-altering events, your attachment style as an infant will probably carry into your adult life.

But it’s not set in stone, and there are a lot of dimensions that can affect it. For example, some scientists believe that if your attachment is insecure, but you’re in a relationship with a secure partner, it can improve your own security—and that makes a lot of sense. If you had a rough childhood, being with someone who is caring and attentive can change your outlook on relationships.

And the reverse is also true. There’s also some speculation that certain relationship experiences— like a nasty break up—could have a negative impact on your attachment, because it can make you feel like you can’t depend on your partners. But we’re still figuring out how exactly our attachment to our parents in childhood impacts our relationships as adults— and how our life experiences change our attachments as we age.

Because adulthood is… complicated, and the paths that take us to it— and to adult relationships—are super variable. One way or another, the research seems pretty clear that our relationships— and the care we’re given as newborns—can have a life-long impact on us. But it’s not always black-and-white:.

Being treated a certain way by your parents won’t automatically mean you grow up to have behavioral problems, or that you’ll be guaranteed to have healthy romantic relationships. So attachment theory is useful in clinical settings and to help predict therapeutic needs, but it’s not the end-all-be-all. I guess what I’m saying is… don’t get too attached to attachment theory.

We’re all different. Thanks for watching this episode of SciShow! If you love learning about psychology and exploring how the mind works, you can find plenty of videos like this one over at youtube.com/scishowpsych. [OUTRO ♪].