In the space of two decades, research has moved from documenting the associations between frontal EEG asymmetry profiles and positive/negative affect, to later reinterpreting these as approach/withdrawal behavior patterns, to documenting individual differences in relationships between EEG and temperament and inhibition/uninhibition. The research has associated greater relative right frontal EEG activation with depression in adults and in depressed women and their infants. Stability of these EEG profiles has been noted from the neonatal stage to early infancy to the preschool years. More recent research assessed mood induction and physical intervention effects on these EEG activation patterns as well as their associated biochemistry and behavior.