A researcher is studying the development of problem-solving skills in children. They theorize that these skills do not improve gradually but rather in sudden, distinct leaps. For example, a child might struggle with a certain type of puzzle for months and then, seemingly overnight, understand the underlying logic and be able to solve it consistently. Which visual metaphor would best represent this researcher's theory of skill development?

A researcher studying how children learn to share toys observes that their behavior changes in abrupt shifts. For several months, a child might refuse to share at all. Then, almost overnight, they begin to share occasionally but only with specific friends. Later, they suddenly start sharing more freely with any peer. Which visual metaphor best represents this researcher's observations of the child's development?