Mary Cover Jones (September 1, 1897 – July 22, 1987) was an American developmental psychologist and a pioneer of behavior therapy, despite the field being heavily dominated by males throughout much of the 20th century.

Joseph Wolpe dubbed her "the mother of behavior therapy" due to her famous study of Peter and development of desensitization.

[3] Soon after graduating from Vassar College, in 1919, Cover Jones attended a lecture by the noted behaviorist John B. Watson, in New York City.

After publishing the result from the Peter study in 1924, she completed a doctoral dissertation on the development of early behavior patterns in young children.

Jones did not receive attention for her work until the 1960s, when the field of behavior therapy began to coalesce under the leadership of Joseph Wolpe.

She then accepted a position as research associate at the Institute for Child Welfare at Berkeley where she became involved in the longitudinal Oakland Growth Study (OGS).

Some of Jones' contributions include her study of Peter, which laid the foundation for behavior therapy, and her development of desensitization and direct conditioning to overcome fears.

While attending a speech by leading behavioral psychologist, John B. Watson, Cover Jones became interested in his most famous study, the "Little Albert experiment".

In this experiment, an infant was classically conditioned to express a fearful response when a white rat was presented along with a loud noise that shocked the child.

Cover Jones began to wonder if the techniques used by Watson could be used to make children less fearful of a stimulus, in essence reversing his findings.

These thoughts led to her most cited work, a study of the removal of a fear of rabbits through conditioning conducted on a three-year-old named Peter at Columbia University.

[6] Cover Jones began her experiment with the goal of finding the most effective way to eliminate irrational fears in children.

[6] Due to the rediscovery of this research in the 1970s, Cover Jones was considered "the mother of behavioral therapy" by her friend Wolpe and other colleagues.

[9] Within the field of child development, Jones believed there was some evidence that supported the idea that adolescent children who have started maturing (reaching puberty) at an earlier age were perceived and treated differently by their peers and other adults.

[11] In Child Development, the flagship journal of the society of Research and Child Development, published an articles were published by Paul Mussen and Mary Cover Jones (1957, 1958) and that investigated the relationship between physical maturation status and self-concepts in late- and early-maturating adolescent boys and girls, respectively.

Paul Mussen and Mary Cover Jones (1957) conducted a study that investigated the relationship between maturational status and certain aspects of personality during late adolescence.

[11] The following year, Paul Mussen and Mary Cover Jones (1958) replicated the study using late and early maturing adolescent girls.