Barbara Fredrickson

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. She is also the Principal Investigator of the Positive Emotions and Psychophysiology Lab (PEPLab) at the University of North Carolina at Chapel Hill.

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: Top-Notch Research Reveals the 3-to-1 Ratio That Will Change Your Life (2009), a general-audience book that draws on her own research and that of other social scientists. The book's thesis is largely drawn from her work with Marcial Losada, claiming a mathematical ratio for happiness. The ratio, however, was "based on a series of erroneous and, for the most part, completely illusory 'applications' of mathematics." Fredrickson was unable to reproduce the math behind her research published with Losada and in a later response the mathematical models for the paper were formally withdrawn.