Barbara Lee Fredrickson (born June 15, 1964) is an American professor in the department of psychology at the University of North Carolina at Chapel Hill, where she is the Kenan Distinguished Professor of Psychology.
Fredrickson is a social psychologist who conducts research in emotions and positive psychology. Her main work is related to her broaden-and-build theory of positive emotions, which suggests that positive emotions lead to novel, expansive, or exploratory behavior, and that, over time, these actions lead to meaningful, long-term resources such as knowledge and social relationships. She is the author of Positivity, a general-audience book that draws on her own research and that of other social scientists.
Studies from Fredrickson's lab have randomly assigned participants watch films that induce positive emotions such as amusement and contentment, negative emotions such as fear and sadness, or no emotions. Compared to people in the other conditions, participants who experience positive emotions show heightened levels of creativity, inventiveness, and "big picture" perceptual focus. Longitudinal studies show that positive emotions play a role in the development of long-term resource such as psychological resilience and flourishing.
The undoing effect 
Fredrickson and others hypothesize that positive emotions undo the cardiovascular effects of negative emotions. When people experience stress, they show increased heart rate, higher blood sugar, immunosuppression, and other adaptations optimized for immediate action. If individuals do not regulate these changes once the stress is past, they can lead to illness, such as coronary disease, and heightened mortality. Both lab research and survey research indicate that positive emotions help people who were previously under stress relax back to their physiological baseline.
Sex differences in self-objectification 
Prior to her work on positive emotions, Fredrickson researched social and environmental cues that can carry sexist messages and enhance stereotypical gender differences. She found that when women are randomly assigned dress in a way that calls attention to their bodies, they show impaired performance on a math task and were literally more likely to "throw like a girl". This research suggested that drawing attention to women's bodies also activated stereotypical beliefs about their gender.
Fredrickson received the Templeton Prize in Positive Psychology in 2000 for her work on the broaden-and-build theory, which included a $100,000 grant to fund her work. Her work has been supported by grants from the National Institute of Mental Health.
Selected publications 
- Fredrickson, Barbara (2009). Positivity. New York: Crown.
- U.S. Public Records Index Vol 1 (Provo, UT: Ancestry.com Operations, Inc.), 2010.
- Fredrickson, B. L. (2003). The value of positive emotions. American Scientist, 91, 330-335.
- Fredrickson, B. L., Mancuso, R. A., Branigan, C., & Tugade, M. M. (2000). The undoing effect of positive emotions. Motivation and Emotion. 24, 237-258.
- Fredrickson, B. L. Roberts, T., Noll, S. M., Quinn, D. M., & Twenge, J. M. (1998). That swimsuit becomes you: Sex differences in self-objectification, restrained eating and math performance. Journal of Personality and Social Psychology, 75, 269-284.