The study of early emotional life reveals much about the nature of development. First and foremost, it becomes clear that development entails a particular kind of growth or unfolding wherein what emerges derives in a logical, though complex way from what was present before as a precursor. The “emergent” is qualitatively different from the precursor and at a new level of complexity; yet the precursor serves as a prototype for the emergent, embodying an important core essence of that which is to come.

The joy in peekaboo, for example, which involves among other things anticipation, coordination of a stored image with a present experience, and some degree of person permanence, is qualitatively different from the newborn's sleep smile or the 10-week-old's pleasure smile to familiar faces, but all three experiences involve the arousal (or tension) modulation core that is central in the reaction.

Likewise, guilt is a qualitatively more sophisticated and differentiated reaction than shame. Guilt involves a deviation from an internalized standard for behavior, entailing a threat to self-esteem and a desire for atonement.