In the 1990s, psychologist John Sottman hit on what he calls the “magic ratio” of five positive for every negative interactions while studying factors that contribute to divorce. He realized he could predict, after one 15-minute conversation with newlyweds, whether they would be divorced in ten years, based on the ratio of positive to negative interactions in that brief time.
Since then, the effectiveness of praise in increasing productivity and the validity of the five-to-one ratio has been confirmed by extensive studies in business settings. Consultant Marcial Losada (working with academicians Barbara Fredickson, Ph.D. and Emily Heaphy, Ph.D.) even established a minimum baseline–the Losada line–for well-balanced, productive teams.
When the praise/criticism ratio falls below 2.9, team performance falters.