The scene is a familiar one: an urban park, with young couples picnicking, dog owners playing fetch, parents chatting while their children scamper around. Marie – a young child – becomes entranced by a new wonder of her world – maybe a springtime butterfly, maybe another child throwing an impressive fit. Eventually, looking away from her intense focus, she realises that the world has shifted around her and that her parents are no longer in sight. Interest and elation morph into concern and fear, as she holds back her tears and begins to search. Just around the corner, she finds her father, who scoops her up, and, as quick as her fear started, it dissipates; her world is complete and safe again.
From the moment we are born, we are hardwired to seek attachment to others. Throughout our lives, relationships that involve attachment serve as sources of emotional security, joy and companionship, while at other times, pain and grief. Compared with those of other animals, human relationships are staggeringly multifaceted. Yet despite this, what lies at the core of our relationships is an elaboration of a phenomenon whose roots across the species spectrum are wide and deep. As we wend our way through life’s course – from infancy to adolescence to adulthood to loss – attachment holds a strong grip on our lives, shifting to accommodate our changing needs. While the roots of this phenomenon tell us much about who we are, they tell us just as much about mysteries that remain unanswered in evolution, psychology, neuroscience and more.
In The Conquest of Happiness (1930), the British philosopher Bertrand Russell wrote:
Those who face life with a feeling of security are much happier than those who face it with a feeling of insecurity … The child whose parents are fond of him accepts their affection as a law of nature … The child from whom for any reason parental affection is withdrawn is likely to become timid and unadventurous, filled with fears and self-pity, and no longer able to meet the world in a mood of gay exploration.
What Russell was describing would only later in the 1930s get a scientific description, when the Austrian zoologist Konrad Lorenz observed that ducks and geese are hard-wired to become attached to the first moving figure they encounter in their life, and will demonstrate signs of distress if separated from that figure. Lorenz found this innate drive to be so strong that attachment happens regardless of whether it’s to the birds’ mother, a bicycle tire or Lorenz himself.
While it’s more complicated for human babies, in the 1950s, the British psychologist John Bowlby extended this concept to us. He observed that children who were separated from their families during the air raids of the Second World War first tended to cry out in protest while seeking them out, then would lie in vigilant despair, then become detached. Bowlby’s observations led to his principle that children, from day one, begin to develop unique mental models of how their primary caregivers recognise and respond to their needs. In effect, these caregivers serve as a base from which to explore the world and, in doing so, become the first of many attachments we experience in our lives. As Bowlby wrote:
All of us, from the cradle to the grave, are happiest when life is organised as a series of excursions, long or short, from the secure base provided by our attachment figures.
The importance of this secure base can hardly be understated. Imagine our park denizens in the age of the Second World War. Kai – a child who plays at that park – is evacuated to live in the peaceful countryside without his parents. Another park child, Marie, remains in London, and experiences bombings and war-related events but in the company of her parents. While perhaps not intuitive – after all, Kai’s parents also had their child’s safety at heart – those who stayed in London with their parents, despite the constant threats of bombings, ultimately fared better psychologically.
But why are we – or any other species – innately driven to form attachments? As the Ukrainian American geneticist Theodosius Dobzhansky wrote in 1973: ‘Nothing in biology makes sense except in the light of evolution.’ In infancy, attachment behaviours such as crying likely evolved to keep caregivers nearby and attentive, so that survival needs could be addressed. This ensures that children become adults and pass on their genes to a new generation; survival and passing on genetic material are ultimately the currency of evolution.
Although the attachment bond that forms between parents and children is universal, many flavours of it exist. In 1978, the American Canadian psychologist Mary Ainsworth described how to parse these different styles of attachment. She developed the Strange Situation Procedure, in which she watched infants as their caregiver left them in the room with a stranger and returned later on. By observing the interplay between infant, caregiver and stranger, Ainsworth was able to relate different patterns of attachment to differences in how sensitive and aware mothers were when it came to their children’s emotional needs. If Marie – the butterfly-chasing child from the park – has a consistently sensitive mother, then she will also tend to use her mother’s return to regulate her distress, before returning to exploration without much difficulty. In contrast, Kai might have an inconsistently sensitive mother, leading him to develop an anxious-ambivalent pattern of attachment: a conflicted interplay between showing bursts of anger and clinging to his caregiver when she returns. Yet another child – Pierre – might have a cold and insensitive mother, leading him to develop an avoidant attachment style, evidenced by a tendency to pull away when reunited, seemingly in an attempt to be self-reliant in regulating his own distress.
Why did we evolve the capacity for different attachment styles? Why would an infant become detached when faced with an unresponsive caregiver? We can imagine that such caregivers, especially in the evolutionary past, might have been unresponsive because they were busy trying to survive in a dangerous or resource-scarce environment. A detached and self-reliant attachment style might be the best way to try to keep this caregiver around but without overwhelming them and risking being abandoned. In other words, even insecure attachment styles probably evolved as context-appropriate adaptations that help children survive in the world.
The insights gained from watching infants’ reactions in the Strange Situation Procedure remain foundational today, and it’s clear that styles of attachment – in childhood and beyond – are intimately related to the quality of early caregiver sensitivity. Yet just as we don’t form irreversible attachments to the first moving thing we see, human attachment types ultimately reflect the multifaceted nature of our experiences. People demonstrate a wide spectrum of all sorts of behaviours, including an array of social attachment. Attachment theory alone can’t explain the complete spectrum and, just as with the psychoanalytic frameworks that preceded it, we shouldn’t allow it to.
Existing secure attachments can be a backbone for absorbing and alleviating stresses from new relationships
As we grow older, we venture away from the secure base of our parents and into deeper relationships with peers. In 1973, Bowlby analogised this continuity of attachment behaviour as a railway system in which a traveller leaving a city centre becomes more and more committed to their trajectory over time. How we navigate this trajectory reflects our attachment experiences. For instance, if Kai has already developed an anxious style of attachment, he might tend to demand a greater amount of intimacy and be hypersensitive to signs of responsiveness or its absence. On the other hand, Pierre, who has developed an avoidant attachment style, will tend to minimise intimacy or interdependence in his new relationships. Marie, who has a secure attachment style, might have a greater ability to ignore or forgive temporary unavailability.
Although Bowlby and Ainsworth didn’t endorse romantic or friendly relationships as extensions of attachment behaviour, others have pointed out that, just as childhood attachment figures play a role in providing comfort and alleviating distress, so, too, do peers and romantic partners. This ability to distribute and buffer stress is especially significant in adolescence, amid the turmoil of new friends, first breakups, hormonal changes and more. It might not surprise you, then, that like Marie, adolescents who have secure attachment styles tend to develop more positive coping skills than their insecurely attached peers, who are more prone to a variety of maladaptive outcomes, including symptoms of depression. In part, this might be because existing secure attachments can be a backbone for absorbing and alleviating stresses from new relationships. Those who come from a world of insecure attachments don’t have the same luxury.
Altogether, early life attachments serve as training grounds for the adult bonds that we go on to engage in. Regardless of attachment style, all of us tend to be drawn towards the allure of falling in love and forming romantic relationships that are hallmarked by pair bonding. Within the context of these bonds, Kai, Pierre, and Marie’s adult attachment styles are likely to be similar to what they were in their early lives, by turns demanding, pulling away from, or exhibiting confidence in their respective relationships. But as with most complex behaviours, attachment styles are not set in stone; individuals can shift towards or away from different ends of the spectrum, especially when faced with experiences such as an unexpected infidelity or an unusually caring partner. Although we know relatively little about the wilful change of attachment styles, we do know that it’s possible, and that, if adults choose to, therapy and self-knowledge can be a catalyst.
Pair bonds form the core of social monogamy, a mating system that arose independently throughout the animal kingdom, and is found in less than 10 per cent of mammals. (Social monogamy involves paired living arrangements between adult males and females, versus genetic monogamy, in which adults pair-mate strictly with each other for life.) Social monogamy had a particularly late emergence in the primate lineage, and it remains our preferred mating system as humans. There is no single answer to why social monogamy has emerged over and over through the course of evolution but, in all cases, pairing up must have provided an evolutionary benefit. For our predecessors, this benefit might have helped in producing more offspring but, more importantly, it might have helped to maximise the ability of those offspring to pass on their own genes to the next generation.
In a dangerous or resource-poor environment, pair bonding might have enabled our mammalian species – in which the presence of the mother is required for nursing – to thrive. The ongoing presence of the father might have been essential for the survival of offspring who might otherwise be killed by a different male aiming to end the pause in female fertility that often accompanies breastfeeding. Other arguments invoke mate scarcity, meaning that a male might have been better off sticking around and waiting for a sequential mating opportunity with the same female, rather than leaving and hoping to find another mate. And in some cases, selective pressures might have had little to do with the surrounding physical environment, and more to do with avoiding pathogens; a limited number of mating partners is an excellent way to avoid passing on sexually transmitted infections.
Regardless of the specific pressures that led to pair bonding, what emerged was that our hominin ancestors paired up to raise children together, in the setting of hunter-gatherer tribes in which mothers and fathers probably had equality in residential decision-making. The presence of two caretakers enabled, for the first time, simultaneous care for multiple dependent children, which, during our evolutionary past, was nearly impossible for a mother to do alone. The source of this additional care wasn’t necessarily the father, either; one counterargument is that the survival of grandmothers well beyond their reproductively active years – a trait not seen in other primates – was selected for because it helps to provide such care.
Attachment theory can help all families by informing social policy
In any case, the prolonged supply of resources for children provided the time and energy required for us to grow larger, more complex brains. The relationship between social bonds and brain size is probably bidirectional, too, with the emergence of more complex brains also leading to more complex social relationships. As a result, we as a species are capable of tremendous flexibility, and employ a variety of social organisations – polyandry, polygyny, polyamory, serial monogamy, and others – depending on factors that include culture, religion and the distribution of resources in society. However, what remains a universal human truth – even in societies that don’t demonstrate pure monogamy – is that we all rely on bonds. We are unaware of any documented culture in which humans are truly solitary creatures who raise their offspring in isolation.
Although we can’t point to universal evolutionary reasons for specific attachment styles, we know that their diversity and continuity should be interpreted in the context of broader socioeconomic factors. In other words, the reason why Pierre develops an avoidant attachment style while Marie develops a secure one goes far beyond factors that are purely intrinsic to their parents. While many parents valiantly provide excellent care even in the face of challenges beyond their control, there remain very real constraints that are related to societal and economic realities. These constraints, which in the US include a lack of compensated parental leave, contribute to an uphill battle in finding the time and energy to provide emotional sensitivity, and thus secure attachment. Likewise, no parent is a blank slate, and Pierre’s parents might themselves have come from an upbringing of insecure attachment or, even worse, exposure to abuse or trauma. This highlights the age-old adage that ‘it takes a village’ to raise our children; attachment theory can help all families by informing social policy. Decades ago, Bowlby’s ideas helped to bring about a policy that we take for granted today: that parents are routinely admitted to hospitals alongside their children. Modern policy relating to early education, childcare and social assistance could similarly benefit from the perspectives of attachment theory.
Our systems for thinking about attachment are notably limited, however, in their applicability to cultures that differ from those that the US evolutionary biologist Joseph Henrich refers to as ‘WEIRD’: Western, English-speaking, industrialised, rich and democratic. This is especially true in an age in which pair bonds come in many forms and are being progressively less institutionalised into marriage. Differences in bonding preferences should remain disentangled from ethical judgment, and we should be wary of stigmatising natural variations in behaviour. This is especially salient given the history of practices that have harmed neurodivergent children across the behavioural spectrum by carrying out procedures such as restraint and forced eye contact, in the name of providing ‘attachment-based’ therapy. Even if our science someday gives way to a capacity to medically alter the spectrum of attachment behaviour, there will always lie the question of medicalisation and what it means to consider oneself or someone else as disabled.
The neuroscience of attachment imparts yet another layer of richness to our understanding. Consider a young Pierre who derives comfort from a favourite blanket, a college-aged Marie who derives comfort from a daily run, or an adult Kai who derives comfort from meditation or worship. In all of these scenarios, the object of attachment provides a sense of security and reward; it’s likely that many attachment behaviours, including social attachment and even maladaptive attachment to drugs of abuse, recruit overlapping brain mechanisms of reward and motivation.
We can think of these brain mechanisms as a network of circuits that carry different streams of information, selectively sped up or slowed down by a variety of chemicals and moulded by experience. Consider serotonin, a chemical that began to be synthesised more than a billion years ago by unicellular organisms. Among other things, this single chemical has gone on to facilitate the stinging mechanism of coral, the swimming of sea urchins, and the emotional behaviour of humans. Although we remain unable to pin down the symphony of effects orchestrated by this ancient molecule, serotonin is integral for feelings of reward. Perturbations in the serotonin system during early development shape individual differences in anxiety and social behaviour. Serotonin accordingly remains the target of some of the most commonly used pharmacological approaches for treating depression and anxiety. Other chemicals, such as dopamine and endogenous opioids, also play crucial roles in signalling reward. Altogether, across the lifespan, many circuits and chemicals probably serve similar functions across a wide array of attachments.
Yet there is a neuroscience that underlies social attachment, in particular. In the 1950s, the ancient signalling molecule oxytocin was found to be a master regulator of maternal behaviour and physiology by inducing labour and the release of milk during lactation. These physiological actions, however, would serve little purpose if oxytocin didn’t also induce a strong desire in a mother to care for her young.
Attachment behaviours emerge from a sea whose tides are being shaped by genetics, experience and chance
Oxytocin’s role in maternal affiliation led the US neurobiologists C Sue Carter and Thomas Insel to ask whether the same molecule also underlies other forms of attachment. To test this, they turned to a small rodent found ubiquitously throughout the central grasslands of North America, the aptly named prairie vole. Like humans but unlike the more commonly studied laboratory rodents, prairie voles form lifelong pair bonds, sharing a burrow and co-parenting their offspring. In 1992, Carter, Insel and colleagues found that they could keep bonds from forming by blocking oxytocin signalling, or could induce animals into forming a bond if they infused oxytocin. With James Winslow, they went on to show that vasopressin, a cousin of oxytocin that originates from the same ancestral gene and differs from oxytocin in just two chemical locations, is equally important to pair bonding, but only in males. While oxytocin and vasopressin critically modulate adult attachment, they do so not in a vacuum but in concert with the other systems of the brain, which all come together in exerting their effects on individual cells, or neurons.
We know that attachment behaviours ultimately emerge from how this sea of chemicals affects the brain’s neurons, a sea whose tides are constantly being shaped by a combination of genetics, experience and chance. But modern science is only beginning to understand how this all happens, and how it plays out across life in different regions of the brain, from neurons of the hypothalamus, a highly multifaceted survival-focused area, to the prefrontal cortex, which carries out higher-level computations, such as social rank. In our own work, we have often studied the nucleus accumbens, a region that monitors motivation and orchestrates goal-directed behaviour. We have found that neurons in the nucleus accumbens of the prairie vole encode a representation of partners that seems to grow as pair bonds deepen over time. We still don’t know how generalisable these processes are to human experience. What we do know, however, suggests that such complex systems, underpinned by oxytocin and vasopressin, translate the differences between Pierre, Marie and Kai into their biology, shaping their present-day social behaviours. Science is still far from deciphering the biological tapestry of human attachment and how it plays out over time. As Bowlby himself said: ‘Here is still a continent to conquer.’
In the same park where Marie, Pierre and Kai played as children, there might very well be a memorial bench that bears witness to what is perhaps the final manifestation of attachment: loss. The loss of loved ones – parents, partners, siblings, friends – are some of the most traumatic events we undergo in our lives. In her memoir The Year of Magical Thinking (2005), the writer Joan Didion described the process of bereavement as a ‘relentless succession of moments during which we … confront the experience of meaninglessness itself’.
From an evolutionary perspective, the existence of grief has long been a puzzle: why did we evolve this capacity to feel intense pain that can make us unable to return to our previous lives, unable to – as Charles Darwin put it – recover our elasticity of mind? Bowlby’s answer was that grief was not selected for on its own but was rather a byproduct of attachment in general. In other words, our attachments manifest not only as the sense of reward that we derive from being around those we love, but also as the negative emotions we feel when separated from them. Bowlby observed that the response to loss seems to parallel the protest-despair-detachment stages of being separated from a caregiver in childhood. In the case of loss, these negative emotions can’t be relieved through reunion, so the bereaved must instead learn to cope and adapt.
In the novel The Stranger (1942) by Albert Camus, a man named Meursault stands trial for murder. In the case brought against him, the prosecutor tells the jury that Meursault seemed not to grieve even at the death of his mother, suggesting this as more evidence of Meursault’s criminality. This argument is convincing because grief is a universal human experience. However, we now know that, just as attachment is a spectrum, so too is the experience of grief. Most people experience feelings of acute grief followed by an ‘integrated’ grief in which they begin to obtain satisfaction from life again. For many, integrated grief involves a reworking of a relationship rather than its end; bereaved people sometimes characterise this as transitioning from painful to bittersweet memories of their lost loved one. However, Pierre, Marie and Kai are likely to engage in these processes in ways that partially reflect their attachment styles, ultimately affecting how they incorporate the finality of loss into their lives. Bowlby theorised that Pierre’s tendency to be hypersensitive to responses from attachment figures could translate into chronic hyperactivation when faced with loss, leading to a chronic yearning. Conversely, Kai’s avoidant attachment style could translate into a tendency to dissociate or distance himself from thoughts of loss, leading to failure to integrate and accept its finality. Although this theory is too simplistic to capture the complexities of why we each grieve the way we do, there are nevertheless meaningful associations between an avoidant attachment style and poorer grieving outcomes.
Stoic philosophy counsels us to recognise that our loved ones are on loan and cannot be possessed
Perhaps reflecting these individual differences in how we engage in grieving, one in every 10 to 20 people experience a feeling of grief that lives on and on, reflecting a stalling of the normal recovery process. This sort of grief, which is medically known as pathological or complicated grief disorder, can manifest as more than a year of feeling the same degree of pain day after day, the same inability to reengage with friends and hobbies that were previously satisfying. Although many progress through this experience on their own, others often seek out help. Our therapies for helping them are often effective but they’re nevertheless hindered by our limited understanding of the psychological and neurochemical underpinnings of loss. We know similarly little about what happens when Pierre or Marie experience the end of attachments through rejection in adolescence or divorce in adulthood; do the underlying processes resemble those of grief? These sorts of questions will become only more pressing over time, especially given the millions worldwide who are facing or will face the loss of loved ones to the COVID-19 pandemic.
While our attachments are punctuated by the extremes of joyful reunion and painful loss, for most of our lives, the tenor of attachment is best described as somewhere in between. The reality is that, in all social attachment, there are undercurrents of satisfaction and dissatisfaction that can be traced back to a variety of origins, from the actions and inactions of partners, to matters of compatibility and an inexplicable lack of feeling fulfilled. One view that has provided inspiration over many centuries is that particular approaches to attachment can themselves lead to pain and suffering. Stoic philosophy counsels that peace of mind arises from living a life in which we minimise how affected we are by events that lie beyond our control – including events from the social realm, and even when in love – by recognising that our loved ones are on loan and cannot be possessed. Buddhist doctrine also advocates nonattachment – not as a dictate to withdraw from relationships, but as a call to engage in them while recognising the impermanence of those we engage with, just as readily as we recognise the impermanence of our own selves. The Buddhist concept of nonattachment has little parallel with Bowlby’s concept of secure attachment, but has been studied on its own accord, with evidence to suggest that higher levels of nonattachment are associated with more positive interpersonal outcomes. One interpretation is that the self is not viewed as separate from everyone and everything else.
There is an unending tug-of-war in which our sciences try to distil the complexity of the world down to fundamental principles. But it’s impossible for scientific theories to express even a fraction of how it can feel to lose – or reunite with – someone we cherish. These attachments, we rightfully believe, are ours, and not reducible to a set of scientific observations. And yet, there is nevertheless something that we can take away from the science, and that is a call to honour the ineffability of our attachments, knowing that they are built from processes that have evolved their way through billions of years and live on in each of us today. While we might come away with disgust at how a person such as Meursault could seemingly live a life without social attachment, maybe it’s more fitting to feel pity for the life that hasn’t experienced an attachment worth grieving for – and to treasure our own all the more.
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