This is interesting. Perhaps if the breath reminds you to relax and stay on your chosen focus, though I would be doubtful that increased oxygen intake is direct

This is interesting. Perhaps if the breath reminds you to relax and stay on your chosen focus, though I would be doubtful that increased oxygen intake is directly a cause. I'm not sure about increased comprehension directly, because I've heard that the best way is to more actively engage with the material (e.g. by asking yourself questions about what you read), but there may be a link to mindfulness.