Fundamental, first order emotions that are structurally and dynamically simpler (primarily due to a lack of cognitive influence) operating chiefly during early childhood (e.g. joy, fear). They develop earlier, constitute foundations for more complex or secondary emotions, emphasize survival, well-being, functional specificity and initiate fast, often automatic reactions.
Izard, C. (2011). Forms and Functions of Emotion: Matters of Emotion-Cognition Interactions. Emotion Review, 3 (4), 371-378. doi: 10.1177/1754073911410737