Mary Ainsworth (1913–1999)

Mary Dinsmore Salter Ainsworth conducted research in the United States, the United Kingdom, and Uganda, in the mid-twentieth century, on how emotional attachment between mothers and infants impacts development. Together with researcher John Bowlby, she developed the Ainsworth-Bowlby Theory of Attachment, hereafter the ABTA. The ABTA is a theoretical framework that accounts for how and why attachment and separation, particularly between children and mothers, impact psychological and behavioral development. Using her training in clinical psychological assessments, she developed new techniques for assessing security and attachment between infants and mothers. Ainsworth and her colleagues applied those techniques to several long-term studies that provided empirical support for the ABTA. Many of her assessment techniques are still in use as of 2025, and her contributions to the ABTA have enabled researchers to systematically analyze how attachment, security, and separation impact psychological and behavioral development throughout the lifespan, opening new avenues for research and treatment.

Ainsworth was born on 1 December 1913 in a village called Glendale in Cincinnati, Ohio, to Mary and Charles Salter. She was the oldest of three daughters. Her father worked at a manufacturing firm, and both her parents were college-educated. In 1918, her family moved to Toronto, Canada, where she spent most of her childhood and young adulthood. Lenny van Rosmalen, an assistant professor at Leiden University in Leiden, Netherlands, who wrote her PhD dissertation on Ainsworth, explains that Ainsworth was inspired at an early age to study psychology. At age sixteen, Ainsworth began psychology courses at the University of Toronto in Toronto, Ontario.

From 1929 to 1939, Ainsworth completed an undergraduate degree, a master’s degree, and a PhD in psychology at the University of Toronto. In an autobiographical article, she named three mentors who particularly influenced her during her time at the University of Toronto, namely Edward Alexander Bott, the head of the psychology department, Sperrin N.F. Chant, her master’s thesis advisor, and William Blatz, her PhD advisor. After completing an undergraduate psychology degree in 1935, she continued as a master’s student and worked as a teaching assistant for Bott’s introductory medical courses and, later, his courses in experimental statistics. In her autobiographical article, she attributes her scientific perspective to his influence. She gained additional experience with experimentation and analysis with Chant, who mentored her master’s thesis research on galvanic skin responses, which are measures of changes in the electrical conductivity of skin due to emotional arousal, as she surveyed subjects on their attitudes about war.

After completing her master’s degree, Ainsworth continued combining psychological inquiry with clinical assessment techniques in her PhD thesis. Ainsworth notes that Blatz, her PhD advisor, was another influential figure in her life as early as her undergraduate years. Blatz developed a theory in which an infant’s association with their parents as a source of security, or what he called the secure base, enables the infant to develop healthy independence and form relationships with peers and partners later in life. Ainsworth developed novel assessment techniques to survey young adults on their security relationships with their parents and peers. Through all those experiences, Ainsworth gained extensive training in a variety of quantitative assessment techniques, some of which were well-established and others, like Blatz’s, were novel in the 1930s.

Upon completing her PhD in 1939, Ainsworth remained at the University of Toronto as a lecturer before joining the Canadian Women’s Army Corps in 1942 and remaining affiliated with the military until 1946. On 10 September 1939, soon after Ainsworth completed her PhD, the Canadian government declared war on Nazi Germany. For the three years between 1939 and 1942, she took over most of the courses belonging to Bott as he, and most other members of the psychology department, including Blatz and Chant, involved themselves in the war effort. She describes in her autobiographical article that by 1942, she wanted to be where the action was and enlisted. She became an Army Examiner, which entailed assessing recruits and informing officer selection. When the war ended in 1945, her former master’s thesis advisor, Chant, hired her as the superintendent of Women’s Rehabilitation in the Department of Veteran Affairs in Ottawa, Ontario. In her autobiographical article, she describes that, although she was eager to return to academia, her four years in the military provided her with a more clinical perspective, greater knowledge of administration, and an appreciation for multidisciplinary collaboration.

In 1946, Bott offered her a position at the University of Toronto as an assistant professor, which she accepted. She specialized in clinical assessment techniques and authored a variety of works that centered on using Rorschach tests, which are a type of assessment technique where a researcher shows an individual ink blots and prompts them to describe what they see in the abstract images. In 1950, she married Leonard Ainsworth, a graduate student in psychology. That same year, she left her position at the University of Toronto to pursue a research position in London, England. 

After arriving in England in 1950, Ainsworth found a job with John Bowlby at Tavistock Clinic in London. Bowlby shared with Ainsworth an interest in how variables like attachment and security promoted or prevented healthy psychological development, with a particular focus on the relationship with the mother. Bowlby was a physician and researcher with experience observing and treating children who were separated from their mothers. He and a colleague, James Robertson, had undertaken a study of the responses of children who had experienced periods of separation from their mothers. Ainsworth joined the team that was analyzing data, which included Robertson’s work. His work consisted of detailed observations of children before, during, and after periods of separation from their parents due to institutionalization, for example, in hospitals. Bowlby and Robertson came up with a classification system for the different stages of emotional responses that the children displayed, namely, a distressed, despair, and detachment phase.

Ainsworth remained at Tavistock Clinic from 1950 to 1953, becoming closely acquainted with Bowlby’s emerging theoretical framework on attachment. The World Health Organization, or WHO, commissioned Bowlby to write and publish a report on the current state of research on children without families, in 1951. Ainsworth reviewed the documents and literature for that report, and, in a co-authored retrospective article, they describe that the abundance of research linking periods of separation from the mother with developmental issues later in life struck them. Ainsworth describes in her autobiographical article that the Bowlby team’s research intrigued her, and Robertson’s data collection impressed her. She resolved that she would undertake similar research.

However, Ainsworth was not always in agreement with Bowlby’s approach, particularly when Bowlby began using ethology, which is the study of natural animal behaviors, and evolution as the foundation for his approach to attachment. Ainsworth initially expressed skepticism as to whether such an approach was accurate. In her autobiographical article, she described that it was initially difficult for her to doubt the dominant psychological theories of the time, which viewed attachment as a consequence of other, more fundamental, instincts. Bowlby proposed that attachment was an instinct in and of itself, and although Ainsworth tried to dissuade him from his position, she also endeavored to find a way to test it.

In 1953, Ainsworth moved to Kampala, Uganda, upon her husband accepting a research position at the East African Institute of Social Research, where she began her first longitudinal study on infant-mother relationships. While Bowlby and the team at Tavistock Clinic had experience making clinical observations, they primarily interacted with children who were already institutionalized in the UK, mostly in London. Ainsworth tested Bowlby’s developing ideas on attachment by assessing them in a novel setting and with a novel sample. She recruited twenty-eight mother-infant pairs and visited them for observational sessions and interviews every two weeks for nine months. She developed two rating systems, one for the degree of attachment between the infant and its mother and another to categorize the mother’s sensitivity to the infant’s signals, or in other words, the mother’s responsiveness. She found a positive correlation between the security of the infant’s attachment to the mother and the mother’s attentiveness to its signals. In her autobiographical article, she reflects that the Uganda study convinced her of the utility and importance of Bowlby’s approach, which viewed infant-mother attachment as its own set of evolved instincts and behaviors.

In 1955, Ainsworth moved from Uganda to Baltimore, Maryland, and by early 1956, she had joined the faculty at Johns Hopkins University in Baltimore. The faculty at Johns Hopkins was unable to hire her for a full-time position, so her role was a combination of teaching evening courses, supervising students who wanted clinical experience at Sheppard and Enoch Pratt Hospital, a psychiatric hospital in Baltimore, and offering her own services as a clinical psychologist two days a week at the same hospital. She also began a referral-based private practice that primarily focused on treating children.

In the late 1950s and early 1960s, she experienced significant transitions in her personal and professional life. Ainsworth and Bowlby had communicated infrequently after she left the clinic, but in 1959 he visited her in Baltimore, and they renewed their exchanges. She began attending the biennial study groups he hosted at Tavistock Clinic. At one of those meetings, she shared the results of her study, which she did not publish until 1967, thirteen years after conducting it. Another significant transition was her divorce from Leonard Ainsworth. In her autobiographical article, she describes her response to the divorce as depressive, leading her to undertake eight years of psychoanalytic treatment. She further elaborates in the same article that her firsthand experience with psychoanalytic treatment deepened both her interest and respect for psychoanalysis. The last transition she experienced was the ending of her clinical appointment at Sheppard and Enoch Pratt Hospital in 1961. With more time available, Ainsworth began her second longitudinal study titled the Baltimore Longitudinal Study of Attachment, hereafter referred to as the Baltimore project.

Ainsworth, along with several assistants, conducted the Baltimore project from 1962 to 1967. They recruited a total of twenty-six mother-child dyads when the infant was three weeks old and observed them until fifty-four weeks after birth, collecting an average of seventy-two hours of observations for each mother-child dyad. In addition to extensive observational notes, they also developed a testing procedure called the Strange Situation Procedure, or SSP. That twenty-minute scenario involved the mother, infant, and a third person unknown to the infant situated in a room that contained toys. She intended the scenario to stimulate the infant’s curiosity, but the results of the study exhibited more about attachment styles. Initially, it is only the mother and infant in the room, then a stranger joins them, and the mother leaves the infant alone with the stranger, but then soon returns. A second separation occurs when the stranger leaves and the mother leaves again, leaving the infant alone in the room. The final stage occurs when the stranger returns first, and then the mother. Ainsworth assessed the extent to which the infant felt comfortable playing and exploring as a measure of the strength and quality of their attachment and security. The Baltimore project constituted a combination of long-term naturalistic observations with short-term experimental procedures.

Beginning in 1969, Ainsworth published the findings from the Baltimore project in a series of articles. In the retrospective article she co-authored with Bowlby, she reflects on the key takeaways of the Baltimore project in terms of ABTA. She noted that infants who she categorized as insecurely attached showed higher instances of separation anxiety when left alone. In general, she interpreted her findings as bearing out many of Bowlby’s predictions and therefore offering strong evidence for the efficacy of the ABTA. The implementation of the SSP also demonstrated that attachment and separation behaviors varied with context, as infants behaved differently in those scenarios than they did at home. For example, an infant who cried upon separation from its mother at home might behave indifferently when separated from the mother during the SSP. Those findings added further complexity to the variables under consideration in the ABTA, such as considering how the stressfulness of the scenario impacts the attachment behaviors the infants displayed.

In the 1960s and 1970s, no longer stretched between duties at the hospital, university, and private practice, Ainsworth primarily taught and mentored psychology graduate and undergraduate students at Johns Hopkins. Ainsworth and her students conducted several studies that expanded on the ABTA using larger sample sizes, such as a study that implemented the SSP among 106 one-year-olds. Ainsworth also published works expanding on the ethological approach of the ABTA to non-parental attachment bonds. Many of her students went on to faculty and clinical positions and continued to apply the ABTA in new contexts.

In the early 1970s, changes in the Johns Hopkins faculty stimulated Ainsworth to seek a new position, and in 1975, Ainsworth began a faculty position in the psychology department at the University of Virginia in Charlottesville, Virginia. She describes in her autobiographical article that she was the only developmental psychologist on the Johns Hopkins faculty, but that she had support from particular faculty members and intellectual stimulation from research and study groups in which she participated. Those groups included the Tavistock Institute Mother-Infant Interaction Study Group and the Society for Research on Child Development. However, when the supportive faculty members left for other universities, she began to feel as if she had lost her backing in the department and, in her words, restive. The department at the University of Virginia included several developmental psychologists and Ainsworth began as visiting faculty before committing to the full-time position in 1975.

Ainsworth remained at the University of Virginia from 1975 to 1984, primarily teaching and mentoring, but also publishing and contributing to research groups. From 1977 to 1979, she was the president of the Society for Research on Child Development. She was instrumental in establishing the clinical psychology training program at the University of Virginia.

Ainsworth retired from the University of Virginia in 1984, but remained professionally active into the 1990s, also receiving several prominent awards. She continued to consult with and mentor the next generation of attachment researchers, actively participating in coding new SSPs and AAIs, and publishing her own articles. She and Bowlby were co-awarded recognition from the American Psychological Association in 1989, and they continued exchanging ideas via letter until Bowlby’s death in 1990. In 1992, she became a member of the American Academy of Arts and Sciences, and in 1998 she received the Gold Medal Award for Life Achievement in the Science of Psychology from the American Psychological Foundation.

However, both in her own time and more recently, scholars have publicized several critiques of her work. In particular, several scholars have pointed out that the ABTA justifies gendered roles, particularly that of the mother. Some scholars interpreted the Uganda and Baltimore project as arguments in favor of traditional stay-at-home motherhood due to the emphasis on maternal responsiveness for positive developmental outcomes. Ainsworth rebutted that critique in her autobiographical article, indicating that substitutions for maternal responsiveness are possible and that it is the responsiveness, not the maternal, that is most important. She also indicated that infant behavior evolved in a time when the mother often performed the caretaking role and that people better understood some of the anachronisms of the ABTA as anachronisms of evolutionary history.

Despite the critiques, Ainsworth’s theory and experimental procedures have significantly impacted contemporary developmental psychology, according to the writings of her peers, students, and other scholars in the discipline. In the 1998 publication that accompanied her Lifetime Achievement Award, the authors describe that one of the most exciting aspects of Ainsworth’s contributions was that they continued to grow, becoming the most dominant paradigm in developmental psychology. A 2002 publication from the Society for Research on the Child listing the twenty most influential researchers in the field cites Bowlby in the number three position and Ainsworth in number four. Writing in 2015, van Rosmalen indicates that the SSP remains the most commonly used assessment technique in attachment research. In 2023, an author refers to the ABTA as a received idea, meaning it remains a dominant paradigm into the 2020s. As of 2025, many of her students and students’ students continue to do attachment research and expand it in new directions. For example, Mary Main, another researcher who studied attachment, along with her student, expanded the ABTA into the Adult Attachment Interview, or AAI, to assess attachment throughout the lifespan, enabling longer longitudinal studies.

Ainsworth’s personal and professional lives were closely intertwined, and she often referred to her academic community as her family. She did not remarry after her divorce in the 1960s nor did she have any children. In her autobiographical article, Ainsworth indicates what she calls her academic family provided her with a similar delight and gratification as having a family of her own. In the later years of her life, a former PhD student and his wife were Ainsworth’s primary caretakers.

Ainsworth died in Charlottesville, Virginia, on 21 March 1999.

Sources

1. Ainsworth, Mary S., and John Bowlby. “An Ethological Approach to Personality Development.” American Psychologist 46 (1991): 333–41.
2. Ainsworth, Mary S. “Mary D. Salter Ainsworth: An Autobiographical Sketch.” Attachment and Human Development 15 (2013): 448–59.
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