Barbara Fredrickson

Who

American social psychologist, Kenan Distinguished Professor at UNC Chapel Hill. Principal Investigator of the Positive Emotions and Psychophysiology Lab (PEPLab). Known for the Broaden-and-Build Theory of positive emotions.

Broaden-and-Build Theory (1998, 2001)

The theory addresses a puzzle in emotion research: negative emotions have clear survival value (fear → escape, anger → attack), but what evolutionary purpose do positive emotions serve?

Broaden

Positive emotions (joy, interest, contentment, love) broaden cognitive and behavioral repertoires:

Joy → urge to play, be creative
Interest → urge to explore, learn
Contentment → urge to savor and integrate
Love → urge to connect and build bonds

This is the opposite of negative emotions, which narrow attention to specific threats.

Build

Over time, these broadened states build lasting personal resources:

Physical: Health, energy, longevity
Intellectual: Knowledge, creativity, problem-solving
Social: Relationships, support networks
Psychological: Resilience, optimism, identity

The Upward Spiral

Positive emotions create a self-reinforcing cycle: positive emotions → broadened thinking → resource building → more positive emotions. This upward spiral is the mechanism by which small happiness interventions can produce lasting change.

Positivity Ratio (and Controversy)

Fredrickson and Losada (2005) proposed a specific “critical positivity ratio” of 2.9:1 (positive to negative emotions) as a threshold for flourishing. This was later discredited (Brown, Sokal, & Friedman, 2013) due to fundamental mathematical errors in the nonlinear dynamics modeling.

Fredrickson’s updated position: The specific mathematical ratio is withdrawn, but the general principle — that flourishing requires substantially more positive than negative emotional experiences — is supported by other evidence. The exact ratio varies.

The Undoing Effect

Positive emotions can “undo” the cardiovascular aftereffects of negative emotions, helping the body return to baseline faster after stress.

Key Publications

Fredrickson, B. L. (2001). The role of positive emotions in positive psychology: The broaden-and-build theory. American Psychologist, 56(3), 218–226.
Fredrickson, B. L. (2009). Positivity.
Fredrickson, B. L. (2013). Updated thinking on positivity ratios. American Psychologist, 68(9), 814–822.