From The First Idea: How symbols, language and intelligence evolved from our primate ancestors to modern humans by Stanley I. Greenspan and Stuart G. Shanker:
…a baby first learns “causality” not through pulling a string to rign a bell or other similar behavior, as Piaget thought, but through the exchange of emotional signals (I smile and you smile back). Therefore, this early lesson is emotional and cogniive at the same time. At each stage, new cognitive skills are learned from emotional experiences. Even high-level symbolic and reflective thining employs emotional awareness as part of its defining characteristics.