Day by day, bit by bit: Knowledge building mechanisms evolve with development.

Much of human knowledge distills patterns that are consistent across many similar experiences over time, such as the typical layout of a bedroom. This is particularly true of word knowledge. The thousands of words we learn form a stable, interconnected network of word meanings that capture regularities in the way words are typically combined to express ideas, such as that "oranges" are something you can "eat" and similar to "apples". Yet, we know surprisingly little about accumulating knowledge from regularities over time, especially in childhood when building knowledge is paramount. Here, we investigated 4-6-year-old children's abilities to accumulate interconnected word knowledge from regularities experienced repeatedly over a month. Younger children appeared to relearn the regularities anew at each exposure, whereas older children accumulated increasingly strong connections across encounters. These findings point to substantial developmental changes in gradual learning processes that build knowledge over time.