Mary Ainsworth was an American-Canadian female scientist that worked in the field of developmental psychology. Developmental psychology is that study of the concerning the how and why of the changing of humans. Ainsworth was born on December 1, 1913 in Glendale, Ohio, and her parents were Mary and Charles Salter. Mary Salter was a nurse and Charles Salter had a master’s degree in history and worked at a firm in Cincinnati. The Salter family then moved to Toronto in Canada, for the rest of Ainsworth’s childhood. Mary was an intelligent student, and at the age of fifteen, she made a decision to work in the field of psychology. At the University of Toronto, she earned her bachelor’s degree in 1935, her master’s degree in 1936 and her Ph.D in 1939. At graduate school, Ainsworth then studied under William Blatz, her mentor. They studied the security theory, which was a theory where the levels of dependence on parents, would result in different quality relationships with them, and with partners in the future. William Blatz then theorized that a more healthy relationship was created with secure interactions with individuals within the relationship. After graduating the University of Toronto, Mary joined the Canadian Women’s Army Corps in 1942 during World War II, but later returned to Toronto to study and research more into psychology. She was married in 1950 to Leonard Ainsworth who was also a psychologist. Through accompanying Leonard for his career, Mary had met several important and influential psychologists, and particularly John Bowlby, which she joined his research team at the Tavistock Clinic, The team studied the effects of the separation of an infant from its mother, on child development, or the attachment theory. The earliest form of sexual development is an infant’s attachment to their parents. She then left to Africa, to also study the interactions between a mother and its child. Mary observed an Ugandan practice that sent a child away from its mother, and to his/her’s relatives to live. While examining the practice, Ainsworth tried to learn the language of the people and soon grew close and fond of the culture. Infancy in Uganda was a book she later wrote about her research trip to Africa. The book is still considered a classic ethnological study in the development of attachment. After her divorce with Leonard in 1960, Mary Ainsworth was then presented with a opportunity to show her research from Uganda at a study group concerning interaction between the mother and infant. She was asked to define attachment, which she replies with a infant crying when her mother left the room, and reacting positively (such as smiling and bouncing) when the mother returned. Five years later, she started working with Wittig on the Strange Situation Procedure. The procedure assessed differences between mother-infant attachment behavior when an infant was in stressful moment, and how he/she reacted. The procedure was for twenty one minutes. The experiment went like this: First, the child and her/his caregiver go into a laboratory setting and the infant is provided with toys. After a while, a stranger to the young child enters the laboratory setting and tries to make friends and be friendly with the infant. The infant’s caregiver leaves the child with that stranger for a few minutes, returns, then leaves for another few with the stranger. After, the stranger goes back to the setting to comfort the young child, and then her/his caregiver comes in to pick the infant up. During this experiment, they would observe the infant’s exploration with the toys and in general, reactions to his/her caregiver leaving, levels of anxiety with the meeting of the stranger, and reactions to reuniting with his/her caregiver. The twenty six children observed were placed in three groups, anxious-avoidant insecure, secure, and anxious-resistant insecure attachments. The first category called anxious-avoidant insecure attachment was if the infant avoids the caregiver whether she is coming or leaving. The infant doesn’t show many emotions and doesn’t explore much at all, no matter the conditions. Secure attachment is when the infant relies on the presence of his/her caregiver to explore, interacts with the stranger, and shows negative emotions when the caregiver leaves and positive ones when she comes back. The last category, anxious-resistant insecure attachment, is when the infant is already showing distress with the caregiver by his/her side. They acted clingy and hard to calm down once the caregiver would return. A fourth group was created by Mary’s colleague, Mary Main, called disorganized/disoriented attachment. The Strange Situation had also experienced much critique. Other believed there was more emphasis on the mother, and bias because all the participants in the study were middle class Americans. Some felt it was artificial, and some question its validity, whether the timeframe of twenty one minutes was not long enough, and there were too many active variables. Later on in her life, Mary Ainsworth received the G. Stanley Hall Award for developmental psychology, and the Gold Medal for Scientific Contributions. In 1999, at the age of 86, Mary died in Charlottesville, Virginia. Even with her death, Ainsworth’s work lives on. The Strange Situation is now one of the more widely used experiments for child development study and research. Her book Infancy in Uganda reflects on the well-done and ethnological research Mary had done back in Africa. She also inspired others to start large research projects on child attachment, and helped psychologists understand the development of children more.