I'm not aeh, but crystallized intelligence refers to acquired knowledge, or "hard facts," if that helps, which largely depend on personal experience of some sort, whether that's in the form of events, personal experiments, direct learning, etc. For example, vocabulary is built through experience when we read, or when we hear others using terms in their correct contexts. A richer experience of language will naturally assist children in test questions that assume familiarity with the terms used.
This differs from fluid intelligence, which is what we rely on when we experience novel puzzles or challenges, and have to figure them out on the fly. Questions where you have to fill in the blanks for number and geometric patterns rely on this ability.
