What Is Attachment Theory? Definition and Stages

Mother Holding Baby Boy

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Attachment describes the deep, long-term bonds that form between two people. John Bowlby originated attachment theory to explain how these bonds form between an infant and a caregiver, and Mary Ainsworth later expanded on his ideas. Since it was initially introduced, attachment theory has become one of the most well-known and influential theories in the field of psychology.

Key Takeaways: Attachment Theory

  • Attachment is a deep, emotional bond that forms between two people.
  • According to psychologist John Bowlby, in the context of evolution, children’s attachment behaviors evolved to make sure they could successfully remain under the protection of their caregivers in order to survive.
  • Bowlby specified four phases of child-caregiver attachment development: 0-3 months, 3-6 months, 6 months to 3 years, and 3 years through the end of childhood.
  • Expanding on Bowlby's ideas, Mary Ainsworth pointed to three attachment patterns: secure attachment, avoidant attachment, and resistant attachment. A fourth attachment style, disorganized attachment, was later added.

Origins of Attachment Theory

While working with maladjusted and delinquent children in the 1930s, psychologist John Bowlby noticed that these children had trouble forming close relationships with others. He looked into the children’s family histories and noticed that many of them had endured disruptions in their home lives at an early age. Bowlby came to the conclusion that the early emotional bond established between a parent and their child is key to healthy development. As a result, challenges to that bond could have consequences that impact a child throughout their lifetime. Bowlby delved into a number of perspectives to develop his ideas, including psychodynamic theory, cognitive and developmental psychology, and ethology (the science of human and animal behavior within the context of evolution). The result of his work was attachment theory.

At the time, it was believed that babies become attached to their caregivers because they fed the baby. This behaviorist perspective, saw attachment as a learned behavior.

Bowlby offered a different perspective. He said that human development should be understood in the context of evolution. Infants survived throughout much of human history by ensuring they stayed in close proximity to adult caregivers. Children’s attachment behaviors evolved to make sure the child could successfully remain under the protection of their caregivers. Consequently, the gestures, sounds, and other signals infants give off to attract the attention of and maintain contact with adults are adaptive.

Phases of Attachment

Bowlby specified four phases during which children develop attachment to their caretakers.

Phase 1: Birth to 3 Months

From the time they’re born, infants show a preference for looking at human faces and listening to human voices. During the first two to three months of life, infants respond to people but they don’t distinguish between them. At around 6 weeks, the sight of human faces will elicit social smiles, in which babies will happily smile and make eye contact. While the baby will smile at any face that appears in their line of sight, Bowlby suggested that social smiling increases the chances that the caretaker will respond with loving attention, promoting attachment. The baby also encourages attachment with caregivers through behaviors like babbling, crying, grasping, and sucking. Each behavior brings the infant in closer contact with the caregiver and further promotes bonding and emotional investment.

Phase 2: From 3 to 6 Months

When infants are about 3 months old, they start to differentiate between people and they begin to reserve their attachment behaviors for the people they prefer. While they’ll smile and babble at the people they recognize, they won’t do more than stare at a stranger. If they cry, their favorite people are better able to comfort them. Babies’ preferences are restricted to two to three individuals and they usually favor one person in particular. Bowlby and other attachment researchers often assumed this individual would be the infant’s mother, but it could be anyone who most successfully responded to and had the most positive interactions with the baby.

Phase 3: From 6 Months to 3 Years

At about 6 months, babies’ preference for a specific individual becomes more intense, and when that individual leaves the room, the infants will have separation anxiety. Once babies learn to crawl, they will also attempt to actively follow their favorite person. When this individual returns after a period of absence, babies will enthusiastically greet them. Starting at about 7 or 8 months old, babies will also start to fear strangers. This can manifest itself as anything from a bit of extra caution in the presence of a stranger to crying at the sight of someone new, especially in an unfamiliar situation. By the time babies are a year old, they have developed a working model of their favored individual, including how well they respond to the child.

Phase 4: From 3 Years Until Childhood Ends

Bowlby didn’t have as much to say about the fourth stage of attachment or the way attachments continued to impact people after childhood. He did observe, however, that at around 3 years old, children start to comprehend that their caretakers have goals and plans of their own. As a result, the child is less concerned when the caretaker leaves for a period of time.

The Strange Situation and Patterns of Infant Attachment

After moving to England in the 1950s, Mary Ainsworth became John Bowlby’s research assistant and long-term collaborator. While Bowlby had observed that children exhibited individual differences in attachment, it was Ainsworth who undertook the research on infant-parent separations that established a better understanding of these individual differences. The method Ainsworth and her colleagues developed for assessing these differences in one-year-old children was called the “Strange Situation.”

The Strange Situation consists of two brief scenarios in a lab in which a caregiver leaves the infant. In the first scenario, the infant is left with a stranger. In the second scenario the infant is briefly left alone and then joined by the stranger. Each separation between caregiver and child lasted about three minutes.

Ainsworth and her colleagues’ observations of the Strange Situation led them to identify three different patterns of attachment. A fourth attachment style was later added based on the findings from further research.

The four attachment patterns are:

  • Secure Attachment: Infants who are securely attached use their caregiver as a secure base from which to explore the world. They will venture out to explore away from the caregiver, but if they're frightened or in need of reassurance, they will return. If the caregiver leaves they will get upset just as all babies will. Yet, these children are confident that their caregiver will return. When that happens they will greet the caregiver with joy.
  • Avoidant Attachment: Children who exhibit avoidant attachment are insecure in their attachment to the caregiver. Avoidantly attached children will not become overly distressed when their caregiver leaves, and upon their return, the child will deliberately avoid the caregiver.
  • Resistant Attachment: Resistant attachment is another form of insecure attachment. These children become extremely upset when the parent leaves. However, when the caregiver returns their behavior will be inconsistent. They may initially seem happy to see the caregiver only to become resistant if the caregiver attempts to pick them up. These children often respond angrily to the caregiver; however, they also display moments of avoidance as well.
  • Disorganized Attachment: The final attachment pattern is most often displayed by children who have been subject to abuse, neglect, or other inconsistent parenting practices. Children with a disorganized attachment style seem to be disoriented or confused when their caregiver is present. They seem to view the caregiver as a source of both comfort and fear, leading to disorganized and conflicting behaviors.

Research has demonstrated that early attachment styles have consequences that reverberate for the rest of an individual’s life. For instance, someone with a secure attachment style in childhood will have better self-esteem as they grow up and will be able to form strong, healthy relationships as adults. On the other hand, those with an avoidant attachment style as children may be unable to become emotionally invested in their relationships and have difficulty sharing their thoughts and feelings with others. Similarly those who had a resistant attachment style as one-year-olds have difficulty forming relationships with others as adults, and when they do, often question whether their partners truly love them.

Institutionalization and Separation

The necessity of forming attachments early in life has serious implications for children who grow up in institutions or are separated from their parents when they're young. Bowlby observed that children who grow up in institutions often don’t form an attachment to any adult. While their physical needs are attended to, because their emotional needs aren’t fulfilled, they don’t bond with anyone as infants and then seem incapable of forming loving relationships when they get older. Some research has suggested that therapeutic interventions might help make up for the deficits these children experienced. However, other events have demonstrated that children that haven’t developed attachments as infants continue to suffer from emotional issues. Further research is still required on this topic, however, one way or another, it seems clear that development proceeds best if children are able to bond with a caretaker in their first years of life.

Separation from attachment figures in childhood can also lead to emotional problems. In the 1950s, Bowlby and James Robertson found that when children were separated from their parents during extended hospital stays—a common practice at the time—it led to a great deal of suffering for the child. If children were kept from their parents for too long, they seemed to stop trusting people, and like the institutionalized children, were no longer able to form close relationships. Fortunately, Bowlby’s work resulted in more hospitals allowing parents to stay with their young children.

Implications for Child-Rearing

Bowlby and Ainsworth’s work on attachment suggests that parents should see their babies as fully equipped to signal what they need. So when babies cry, smile, or babble, parents should follow their instincts and respond. Children with parents who promptly respond to their signals with care tend to be securely attached by the time they are a year old. This doesn’t mean that parents should take the initiative to go to the child when the child hasn't signaled. If the parent insists on attending to the child whether the infant is signaling their desire for attention or not, Bowlby said the child can become spoiled. Bowlby and Ainsworth felt, instead, caretakers should simply be available while letting their child pursue their own independent interests and explorations.


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  • Cherry, Kendra. “The Different Types of Attachment Styles” Verywell Mind, 24 June 2019. https://www.verywellmind.com/attachment-styles-2795344
  • Crain, William. Theories of Development: Concepts and Applications. 5th ed., Pearson Prentice Hall. 2005.
  • Fraley, R. Chris and Phillip R. Shaver. “Attachment Theory and Its Place in Contemporary Personality Theory and Research.” Handbook of Personality: Theory and Research, 3rd ed., edited by Oliver P. John, Richard W. Robins, and Lawrence A. Pervin, The Guilford Press, 2008, pp. 518-541.
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Vinney, Cynthia. "What Is Attachment Theory? Definition and Stages." ThoughtCo, Dec. 6, 2021, thoughtco.com/attachment-theory-4771954. Vinney, Cynthia. (2021, December 6). What Is Attachment Theory? Definition and Stages. Retrieved from https://www.thoughtco.com/attachment-theory-4771954 Vinney, Cynthia. "What Is Attachment Theory? Definition and Stages." ThoughtCo. https://www.thoughtco.com/attachment-theory-4771954 (accessed March 27, 2023).