Barbara Fredrickson is an America Professor of Psychology at North Carolina. She has written extensively on positive emotions and links with resilience, and worked with Marcel Losado on the Losado ration. She has developed the broaden and build theory of positive emotions.
Barbara's book Positivity looks at
You can find out more about Barbara's work at her website: http://www.positivityratio.com/index.php
Below is Barbara's YouTube video Positive Emotions Transform Us