In humans, nearly a quarter of children grow up with a disorganized attachment style — the most extreme form of insecure attachment, linked to trauma, fear, and emotional instability. But in the West African forests of Taï National Park, researchers just spent nearly 4,000 hours observing wild chimpanzee mothers and their young — and they didn’t see a trace of it.
The new study published today in Nature Human Behaviour delivers the first field evidence that wild chimpanzees form organized attachments to their mothers — secure or insecure-avoidant — but never disorganized. The implications challenge long-held assumptions about human attachment.
“We found no evidence of disorganized attachment in wild chimpanzees, unlike in humans and in orphaned chimpanzees raised in captivity,” says Eléonore Rolland Institute of Cognitive Sciences Marc Jeannerod, in an email to ZME Science. “This supports the idea that disorganized attachment may not be an evolutionarily adaptive strategy in high-risk environments like the wild.”
“However, we did observe clear individual differences that aligned with recognized human attachment patterns — specifically, secure and
insecure-avoidant types. This suggests that the attachment system is deeply rooted in our evolutionary past and may operate similarly across species in certain contexts.”
Disorganized Attachment May Be a Human Problem
Psychologists identify four main types of attachment, based on how infants respond to stress and their caregiver’s availability. Secure attachment is the healthiest, most adaptive type. Insecure-avoidant attachment is linked to more independent behavior but also suppressed emotional needs. Insecure-resistant (or ambivalent) attachment is linked with clinginess and anxiety. The most troubling one is disorganized attachment. This is linked to emotional dysregulation, mental health problems, and difficulties forming stable relationships.
The study challenges a common belief: that all human attachment types are equally rooted in evolution. They’re not. Disorganized attachment, with its confused, fearful approach-avoidance behavior, doesn’t seem to show up in the wild.
If a baby chimp doesn’t know whether to run to or from its mother when scared, it may freeze at the worst possible moment. That’s not a useful strategy. It’s a glitch. In the unforgiving wild, such glithces are quickly wiped out. But if human infants develop disorganized attachment in environments where there’s no predator to tax you — well, that glitch can persist.
In this study, none of the wild chimpanzees showed signs of “disorganized” attachment.
“Our findings suggest that humans and chimpanzees share foundational aspects of attachment behavior, indicating that this system has deep evolutionary roots. At the same time, environmental conditions play a significant role in shaping how attachment is expressed.”
“For example, disorganized attachment seems to emerge more frequently in environments where offspring are not exposed to survival threats, such as in captivity or modern human societies.”
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A Look At Chimps
To find out how wild chimpanzee infants form bonds with their mothers, researchers followed 50 young chimps — ranging from newborns to ten-year-olds — for over 3,700 hours in Taï National Park, Côte d’Ivoire. They watched how these infants behaved during real-life stressful events: sudden aggression nearby, alarm calls, loud noises in the forest. These were natural threats, the kind that actually matter for survival in the wild.
They focused on what the chimps did in these moments of fear — did they run to mom, stay put, or act independently? Using a detailed catalogue of behaviors, they tracked each infant’s responses and analyzed patterns over time. To detect attachment styles, they applied machine learning techniques to identify behavioral clusters, similar to human categories like “secure” and “insecure-avoidant.”
As none of the chimpanzees showed the erratic, conflicted behaviors that define disorganized attachment in humans and captive chimps, this suggests that such responses may not be viable in the wild.
“In humans, attachment is often assessed using the Strange Situation Procedure, where infants are briefly separated from their caregiver and reunited, and their responses are observed. Since such an experimental setup isn’t possible and is unethical in the wild, we developed a non-invasive approach that captures the core principles of attachment theory.”
Some infants would immediately seek comfort from their mother, while others would move away independently. “These consistent behavioral differences allowed us to identify distinct attachment types, regardless of the age of the offspring,” the researcher adds.
In humans, disorganized attachment is surprisingly common: about 23.5% of children exhibit it. In orphaned chimps raised in captivity, it’s even more prevalent — 61%. But in the jungle? Nada.
This is the main finding, and it supports the idea that disorganized attachment may not be an adaptive survival strategy in the wild. If you’re a baby chimp, you’re either clinging to mom for dear life, or learning to handle yourself — but you’re not flailing around in a confused mess. Because if you are, you probably don’t survive long enough to pass on your genes.
So, what does this say about us?
This Is Also About Humans
Rolland’s findings suggest that the basic architecture of attachment — secure and avoidant — may be shared across our evolutionary relatives. That makes sense. Across primates (and mammals in general), the ability of infants to stay close to a caregiver during threats is a matter of life and death.
But modern humans don’t face those same threats. We’ve traded leopards for layoffs and community for daycares. We live with the tactile comfort for screens, free from many of the evolutionary pressures shared by our ancestors and our close relatives. In these radically altered environments, attachment patterns may not play out in the same adaptive ways.
“Our results deepen our understanding of chimpanzees’ social development and show that humans and chimpanzees are not so different after all,” says Rolland. “But they also make us think: have some modern human institutions or caregiving practices moved away from what is best for infant development?”
The implication is unsettling. Modern environments — especially those marked by social fragmentation, institutional care, or inconsistent parenting — might inadvertently foster attachment patterns that are out of sync with what our brains evolved to expect.
The rise of disorganized attachment in human societies be a signal that something is off in how we structure early childhood. Studies in humans have shown that consistent, responsive caregiving can prevent disorganized attachment — even in high-risk settings.
They’re continuing to follow the chimpanzees as they grow into adolescence and adulthood.
