Categories are essential for thinking, learning, and communicating. Research has shown that young children and adults treat categories very differently, with young children favoring whole objects while adults focus on the key information in most cases. If so, then how can young children learn categories requiring focused attention to key features? Studies have shown that drawing attention to rules had facilitative effects. We sought to identify whether the effect was driven by instruction about rules or by stimulus-driven factors. Our results suggest that even with instruction, 4-year-olds were not able to attend to key information. Simply making important information more salient, however, allowed them to learn the category and transfer to situations when the key feature was no longer salient.