This particular thought occurred to me the first time when I was in the UK. All of a sudden, when deeply engaged in reading the heavy philosophical texts as part of my study, it hit me that I was not really paying attention to what I was reading! It was true that I wasn't distracted, or was not paying attention to the text I was reading, just that my mind was simultaneously busy with something else.
I could conveniently read a text and still be gladly letting my mind think of something else altogether, without breaking the flow of reading. I tried if reading aloud helped me concentrate on the text, rather than let my mind be on something else and surprisingly I found that it was easier that silent reading!!
I couldn't get my mind around this strange phenomenon that I noticed in myself and tried to see how and where could I have picked up this habit of disconnecting my eyes, mouth and mind! I soon found the source: during prayer! One day, sooner than later, it struck me that I was praying the breviary, the psalms, but my mind was elsewhere. That's when it hit me that over the years, I've learnt to think of something totally unrelated to what I am reading - thanks to my community prayer moments! I can confidently, in a loud and clear voice, read the psalms from the breviary, all the while thinking about my office work or plan a budget!
Over the years I've tried to break this unhealthy habit, but with no success. I realise I've deeply imbibed it unconsciously, perhaps.