Reading Projects for undergraduates
Whether it is during your interview, or when they read you SoP, there will always read your enthusiasm between the lines. If you happen to be doing some self-study by yourself, it clearly shows that you are personally interested in the subject and enthusiastic about it. 

Plus, by doing undertaking such projects, you will have a much wider perspective about the field and you will be familiar with more complex ideas. So, when they ask you "why do you want to work on this field", you can give a much more specific answer than "I find it interesting".