Example: Vosniadou's research examining the development of children's conceptions of the earth (flat earth - pancake (combining spontaneous notion of flat with learned formal notion of round earth), dual-earth (one round that is depicted on globes, shots from moon; one flat that we live on), hollow earth (live inside a hollow sphere)
Example shows how spontaneous and formal notions meet and shift the child's concepts.
Example: Bruner's Spiral curriculum. Concepts revisited at higher levels of abstraction or formalism as children progress through the curriculum.