Reading a text once is useful, the second time it just seems so. When you read something for the first time, you extract new information from it. When you reread a text, you recognize it. Because you recognize the text, you think you know it by heart. However, recognizing a text is not the same as truly knowing it by heart and, for example, being able to answer questions about it. Because you recognize the text, you think less deeply about it, which means you also learn less. In this way, your brain is actually fooling you. What works much better is to write down from memory what you remember after some time (and then look up what you don't remember), answer questions about the text, or create a diagram of the learning material. In this way, you learn more actively.
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