Photo of Mary Koss

Mary Koss

Training Location(s):

PhD, University of Minnesota (1972)

BA, University of Michigan (1970)

Primary Affiliation(s):

Kent State University (1976–1988)

University of Arizona (1988–present)

Career Focus:

Sexual violence, restorative justice, campus sexual assault.


Mary Koss is American Regents’ Professor in the Mel and Enid Zuckerman College of Public Health at the University of Arizona. Her scholarly research and advocacy have contributed significantly and impactfully to the ways that violence against women is conceptualized and addressed in public policies at national, state, and local levels.

Born in Louisville, Kentucky, Koss was raised by her maternal grandparents while her mother recovered from polio. After graduating high school at age 17, Koss went on to earn her Bachelors degree in Psychology from the University of Michigan and her PhD in Clinical Psychology from the University of Minnesota-Twin Cities.

In 1978, while working as a Psychology Professor at Kent State University, Koss was recruited by the Victims of Violence Center and the National Institute of Mental Health to facilitate a study on rape prevalence. This 1987 study entitled “The Scope of Rape: Incidence and Prevalence of Sexual Aggression and Victimization in a National Sample of Higher Education Students” was the first large-scale, national study on rape prevalence rates. The study highlighted the inadequate methods that had been used to measure rates and experiences of sexual violence, resulting in underreporting as reflected in national crime statistics, convictions, and incarceration rates related to sexual assault.

This study led to Koss being credited with coining the terms “date rape,” “acquaintance rape,” and “campus rape.” It consisted of a sample of 6,159 students enrolled in 32 higher education institutions in the United States and demonstrated that rape occurs at far higher rates than were previously believed or reported in the research literature. According to the study, 27.5% of college women reported experiencing rape and 7.7% of college men reported perpetrating rape. In addition, the study revealed that one quarter of college women had experienced attempted or completed rape before the age of 14, and that then-current statistics on rape prevalence and victimization rates reported in official surveys such as the National Crime Statistics were inaccurate and lower than what was actually experienced.

Koss asserted that research reports at the time reflected the experiences of rape victims who had been recruited through ads, police and court records, and who were victims who sought help at rape crisis centers or emergency rooms. Yet “hidden victims” whom Koss described as those who “do not report rape, seek services, or even identify themselves as rape victims” should also receive attention in future research studies. Information on the “hidden rape victim” was elaborated in Koss’s 1985 study entitled “The Hidden Rape Victim: Personality, Attitudinal, and Situational Characteristics.” Koss identified and described the “hidden rape victim” as “one who has never reported her experience to a rape crisis center or to police.” Koss argued that the number of unacknowledged rape victims, those who experience behaviors that constitute legal definitions of rape, but who do not conceptualize these experiences as rape, may be far greater in number than victimization studies suggest. The study also found that most of the hidden rape victims experienced assault perpetrated by an acquaintance; in fact, 84% of the rapes reported in Koss's study were perpetrated by someone the survivor knew. Through this novel and innovative research, Koss raised awareness among the public of not only the actual scope and magnitude of rape prevalence rates, but also of how often the research literature fails to capture the experiences of rape victims and hidden rape victims.

Koss experienced harsh backlash for her research in 1990 when she was asked to testify about her findings to the State Judiciary Committee. This was shortly after then-Senator Joseph Biden had introduced the Violence Against Women Act. Biden had frequently used Koss’s 1 in 4 statistic to advocate for the necessity of the bill and for stronger legal protections for survivors of gender-based violence. Yet critics believed that the bill could be easily undermined by distorting Koss’s research findings on rape prevalence rates and therefore federal funding could be allocated to problems they deemed more important. Despite the criticism that she faced, the methods that Koss used in her research became the standard for studying rates of sexual violence on college campuses. Koss’s research laid the foundation for a generation of researchers who continue to survey and study sexual violence, and it is clear that she has had a lasting impact on how sexual violence is researched, measured, and addressed in both federal policy and in higher education.

Most recently, Koss has proposed a rehabilitation-focused alternative for dealing with perpetrators of sexual assault and the problem of sexual violence in higher educational institutions. From the years 2002-2007, Koss worked as the principal investigator of the RESTORE Program, the world’s first restorative justice program of its kind for committed sex offenders. Part of the restorative justice program involves voluntary, supervised conferences where primary and secondary victims communicate with the perpetrator about the harm that has been committed, and formulate a redress plan together with the perpetrator. The RESTORE program is now being used as a foundational model by the Office of the National Institute of Justice in their goal to offer a non-adversarial option for those who commit acts of sexual violence. Following her study on the outcomes of the RESTORE Program, Koss has reported that it has the potential to achieve greater justice for survivors of gender-based violence.

In 2000, Koss received the American Psychological Association Award for distinguished contributions to research in public policy for her work on gender-based violence, and in 2006 she became a University of Arizona Regents Professor, an honorary title given to only the top 3% of university professors who have made significant contributions to their fields of research. Her body of work was recognized in 2019 with the Carolyn Wood Sherif Award, the most prestigious award given by the Society for the Psychology of Women of the American Psychological Association.

Throughout her career, Mary Koss has been a trailblazer who has boldly conducted research that has increased our knowledge of sexual violence. She has not only created mechanisms for survivors of sexual assault to have greater access to justice, but has also succeeded in ensuring that scientific research conveys the lived realities of those who have experienced gender-based violence.

By Shalyn Isaacs (2020)

To cite this article, see Credits

Selected Works

Selected Works By

Koss, M. P. (1985). The hidden rape victim: Personality, attitudinal, and situational characteristics. Psychology of Women Quarterly, 9(2), 193-212.

Koss, M. P., Gidycz, C. A., & Wisniewski, N. (1987). The scope of rape: Incidence and prevalence of sexual aggression and victimization in a national sample of higher education students. Journal of Consulting and Clinical Psychology, 55(2), 162-170.

Koss, M. P., & White, J. W. (2003). National and global agendas on violence against women: Historical perspective and consensus. American Journal of Orthopsychiatry, 78(4), 386-393.

Koss, M. P. (2011). Hidden, unacknowledged, acquaintance, and date rape: Looking back, looking forward. Psychology of Women Quarterly, 35(2), 348–354.

Koss, M. P. (2014). The RESTORE Program of restorative justice for sex crimes. Journal of Interpersonal Violence, 29(9), 1623-1660.

Donde, S. D., Ragsdale, S. K., Koss, M. P., & Zucker, A. N. (2018). If it wasn't rape, was It sexual assault? Comparing rape and sexual assault acknowledgment in college women who have experienced rape. Violence against Women, 24(14), 1718-1738.

Koss, M. P. (2018). Developing and implementing a treatment intervention for college students found responsible for sexual misconduct. Agression, Conflict, and Peace Research, 10(2), 134-144.

Selected Works About

Award for Distinguished Contributions to Research in Public Policy: Mary P. Koss. (2000). American Psychologist, 55(11), 1330-1332.

Rutherford, A. (2017). Surveying rape: Feminist social science and the ontological politics of sexual assault. History of the Human Sciences, 30(4), 100-123.