Classics in the History of Psychology

An internet resource developed by
Christopher D. Green
York University, Toronto, Ontario

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Introduction to

"A Laboratory Study of Fear: The Case of Peter"
Mary Cover Jones (1924)

Alexandra Rutherford, York University

© 2001 Alexandra Rutherford
All rights reserved.

Mary Cover Jones was christened "the mother of behavior therapy" in the early 1970s by colleague and friend Joseph Wolpe, and has been portrayed throughout the psychological literature as a pioneer in the field of behavior therapy because of her seminal research on the unconditioning of the fear reaction in infants. Her study of the three-year-old named Peter has probably been cited more extensively than any other aspect of her work (see Jones, 1924), and is commonly referred to as the follow-up to Watson and Rayner’s "Little Albert" experiment (Watson & Rayner, 1920). Closer examination of Jones' career, however, reveals a rich and personologically-oriented approach to the study of personality across the lifespan that is overshadowed by the now mythic status of the Peter study.

Mary Cover was born on September 1, 1897, in Johnstown, Pennsylvania. After graduating from high school in 1915, she enrolled at Vassar College. At Vassar she took "every psychology course offered" (Reiss, 1990, p. 205) -- except one. She could not attend Margaret Floy Washburn's senior seminar in psychology because of a mediocre grade in an earlier laboratory course. When pressed, Washburn declared, "You wouldn’t enjoy the Senior Seminar, it's just like that sophomore lab course that you didn't like!" (Jones, cited in Reiss, 1990, p. 206). Despite Washburn's rejection, Mary Cover graduated from Vassar in 1919. In that year, she also attended a weekend lecture given by J. B. Watson in New York City. This lecture, in which he described the Little Albert study undertaken with Rosalie Rayner (a Vassar graduate and friend of Mary's), cemented her desire to pursue graduate work in psychology, rather than pediatric medicine.

To this end, Mary Cover began graduate work at Columbia University in 1919, and completed her Master's degree by the summer of 1920. That same summer she married fellow graduate student, Harold Jones. In 1923, she was appointed Associate in Psychological Research at the Institute of Educational Research, Teachers' College, Columbia University. During this time, Jones conducted her study of Peter under the supervision of J. B. Watson. Watson, although he was no longer working in academia, had been hired by Teachers' College to serve as a consultant on a grant received from the Laura Spelman Rockefeller Memorial to study child development and provide parent education. Briefly, Jones treated Peter's extant fear of a white rabbit with a variety of fear-reducing procedures. The most successful procedure was that of "direct conditioning," in which a pleasant stimulus (food) was presented simultaneously with the rabbit. As the rabbit was gradually brought closer to him in the presence of his favorite food, Peter grew more tolerant, and was able to touch it without fear.

After publishing these results (Jones, 1924), Jones completed a doctoral dissertation on the development of early behavior patterns in young children (Jones, 1926). This work was supported by a fellowship from the Laura Spelman Rockefeller Memorial, and was conducted using a sample of 365 infants from three Baby Welfare Stations in New York City. Ironically, the Little Peter research was not considered appropriate for a doctoral dissertation because of its small sample size. Jones did not receive attention for this work until the 1960s, when the field of behavior therapy began to coalesce under the leadership of Joseph Wolpe.

In the summer of 1927, the Jones family (she now had two young daughters) packed their bags and headed west. Harold Jones had been offered a position as Director of Research at the recently established Institute for Child Welfare at the University of California, Berkeley. Mary took a position as Research Associate and soon became involved in one of three longitudinal studies conducted through the Institute. Her involvement with and commitment to the Oakland Growth Study (OGS) colored the rest of career.

The OGS began in 1932 and was designed to follow a group of approximately 200 fifth- and sixth-grade students from puberty through adolescence. In fact, several follow-up studies were undertaken as members of this group moved into middle and older adulthood, a feat largely attributable to Jones' conscientiousness and personal relationships with the project's members. Many of the study members became her friends and benefited from her support and generosity of spirit.

Jones published over 100 articles using data from the OGS. Among these was a series of studies on the long-term psychological and behavioral effects of early- and late-physical maturation in adolescence (e.g., Jones, 1957). Throughout her published work, she was extremely careful to relay a sense of the uniqueness of individual participants, and often used case studies and idiographic analysis to qualify her statistical results. Despite her behaviorist beginnings, Jones' work reflected an eclectic theoretical outlook and an emphasis on the whole person in his or her developmental, environmental, and social context.

In 1952, at age 56, Jones was appointed Assistant Professor of Education at Berkeley. Strict anti-nepotism rules had precluded her appointment to the psychology department because of her husband's position there. In that year, she and Harold produced the first educational television course in child psychology. In 1959, one year before her retirement, she became full professor. In 1960, she served as president of the Division of Developmental Psychology of the APA. Tragically, in that same year, just months into their retirement, Harold suffered a fatal heart attack.

Jones continued to work productively after Harold's death, and received the G. Stanley Hall Award from APA in 1968. In a keynote address at the first Temple University Conference in Behavior Therapy and Behavior Modification in 1974, she offered this assessment of her career and her personal and theoretical outlook:

[M]y last 45 years have been spent in longitudinal research in which I have watched the psychobiological development of our study members as they grew from children to adults now in their fifties… My association with this study has broadened my conception of the human experience. Now I would be less satisfied to treat the fears of a 3-year-old, or of anyone else, without a later follow-up and in isolation from an appreciation of him as a tantalizingly complex person with unique potentials for stability and change. (Jones, 1974, p. 186)

Mary Cover Jones died in Santa Barbara, California on July 22, 1987. She was almost ninety-one years old. Minutes before she passed away, she said to her sister, "I am still learning about what is important in life" (cited in Reiss, 1990). As a result of her lifelong commitment to learning, Jones was a pioneer in the field of behavior therapy, and made a rich contribution to the understanding of development across the lifespan.


Jones, M. C. (1924). A laboratory study of fear: The case of Peter. Pedagogical Seminary, 31, 308-315.

Jones, M. C. (1926). The development of early behavior patterns in young children. Pedagogical Seminary, 33, 537-585.

Jones, M. C. (1957). The later careers of boys who were early- or late- maturing. Child Development, 28, 113-128.

Jones, M. C. (1968). Personality correlates and antecedents of drinking patterns in adult males. Journal of Consulting and Clinical Psychology, 31, 2-12.

Jones, M. C. (1974). Albert, Peter, and John B. Watson. American Psychologist, 29, 581-583.

Reiss, B. K. (1990). A biography of Mary Cover Jones. Unpublished doctoral dissertation. The Wright Institute, Los Angeles, CA.

Watson, J. B. & Rayner, R. (1920). Conditioned emotional reactions. Journal of Experimental Psychology, 3, 1-14.