Lea Pulkkinen, born in Finland in 1939, is Emerita Professor of Psychology at the University of Jyväskylä (Finland). She is best known for creating the ongoing Jyväskylä Longitudinal Study of Personality and Social Development (JLSPSD). The study was specifically intended to test the hypothesis that the human brain allows for more variation in behavior than the simple ‘fight or flight’ response observed in animal studies of aggression. She further hypothesized that humans’ capacity for cognitive control over emotional behavior was the key factor involved in controlling aggressive behavior. These hypotheses led her to devise an impulse control model to depict behavioral alternatives, which she tested with teacher and peer ratings of aggressive and nonaggressive behaviors. Forty years later, the JLSPSD revealed the long-term significance of self-regulation for socio-emotional behavior. Results from the study showed that aggressive behavior during childhood tends to be associated with other types of under-controlled behavior during adulthood. On the other hand, ‘constructive’ behavior in childhood tends to lead to positive social relations, mental health, and successful integration in the work force.