highlighting and underlining don't per-se cause you to learn. However they do have two useful properties.
1. The act of looking for and underlining or highlighting text helps you to focus on identifying core ideas or concepts in the text.
2. Underlined and highlighted text are useful as hints when reviewing a text and reviewing a text is a critical part of learning.
These properties are so helpful that many texts actively help you to absorb their content by bolding, underlining, or otherwise calling attention to core concepts and ideas for you.
1. The act of looking for and underlining or highlighting text helps you to focus on identifying core ideas or concepts in the text.
2. Underlined and highlighted text are useful as hints when reviewing a text and reviewing a text is a critical part of learning.
These properties are so helpful that many texts actively help you to absorb their content by bolding, underlining, or otherwise calling attention to core concepts and ideas for you.