Expressions as signs and their significance for emotional development.

For research on emotional development, defining emotions as psychological systems of appraisals, expressions, body reactions, and subjective feelings in all phases of ontogenesis raises tricky methodological issues. How can we measure single emotions when appraisals and feelings cannot be assessed from outside, when expressions do not seem to be tied unequivocally to single emotions, and feelings are sometimes decoupled from perceivable expressions? Furthermore, how does a restricted set of neonate emotions differentiate into a culturally modified set of adult emotions? This article presents an innovative answer to these issues by applying Vygotsky's culture-historical approach on the psychological significance of social signs to the analysis of emotion, expression, and their development. The core assumption is that humans learn to use emotional expressions as communicative signs that appeal to another person to regulate their interaction through emotions and as psychological signs that appeal to the self to regulate the self's actions through emotions.