Science texts often use visual representations (e.g. diagrams, graphs, photographs) to help readers learn science knowledge. Reading an illustrated text for learning is one type of multimedia learning. Empirical research has increasingly confirmed the signaling principle's effectiveness in multimedia learning. Highlighting correspondences between text and pictures benefits learning outcomes. However, the signaling effect's cognitive processes and its generalizability to young readers are unknown. This study clarified these aspects using eye-tracking technology and reading tests. Eighty-nine sixth-grade students read an illustrated science text in one of three conditions: reading material with signals, without signals (identical labels of Diagram 1 and Diagram 2 in text and illustration), and with signals combined with reading instructions. Findings revealed that the signaling principle alone cannot be generalized to young readers. Specifically, "Diagram 1" and "Diagram 2" in parentheses mixed with science text content had limited signaling effect for students and reading instructions are necessary. Eye movements reflected cognitive processes of science reading; students who received reading instructions employed greater cognitive effort and time in reading illustrations and tried to integrate textual and pictorial information using signals.