Although often referenced as “Bowlby’s attachment theory,” attachment theory as we know it today was developed by several researchers over the course of the late 20th century. British psychoanalyst John Bowlby developed the concept of attachment behaviors around the 1950s. His theory was that children’s tendency to emotionally attach to their caregivers and to become distressed and seek them out in their absence was an adaptive evolutionary trait, something that allowed children to survive by clinging to an attachment figure who provided support, protection, and care when they were too young to care for themselves.
Mary Ainsworth, a psychologist and one of Bowlby’s colleagues, expanded on Bowlby’s original attachment theory by identifying individual differences in how infants handled separations from their parents. Her famous “strange situation” experiment in 1969 identified four attachment types among infants: secure, anxious-resistant, avoidant, and disorganized.
Later in the 1980s, social psychologists Cindy Hazan and Phillip Shaver began to apply Ainsworth and Bowlby’s attachment theory to adult romantic relationships, giving birth to the concept of the adult attachment styles we know today. In 1998, research psychologist Kelly Brennan and her colleagues further expanded on adult attachment, demonstrating two distinct dimensions that shape attachment patterns: attachment-related anxiety and attachment-related avoidance. People can be low in both, high in one and low in the other, or high in both, which determines their attachment style. (See above graphic.)
Today, there’s some criticism of attachment theory among psychologists who say it’s a stretch to believe caregivers can so dramatically shape infants’ personalities at such a young age. Indeed, thus far, studies attempting to draw a line between infant attachment patterns and their adult attachment styles have only found “small to moderate” correlations, according to Fraley himself. “Based on these kinds of studies, it seems likely that attachment styles in the child-parent domain and attachment styles in the romantic relationship domain are only moderately related at best,” Fraley writes in a University of Illinois article.
But the concept of attachment styles is enduring for a reason: It gives people language to describe the distinct ways they show up in their relationships, and it challenges them to look to their past experiences to help them understand why they are the way they are.