I have a background in languages and linguistics, and I have both feet firmly in the humanist camp, so it quite often happens when I read a scientific text that I ask the author to explain passages to me. I guessed that he had made a mistake when typing, and had wanted to write 'on' instead of 'off' at least once. But when?
When I asked my colleague if he was sure it was correct, he read the sentence and said it was correct. He is a physicist, though, and I thought that he may have just read the equations. In this case, I asked him to tell me if when S=0, the circuit is on or off. "Off", he answered. Next, I asked him if when S=1, the circuit is on or off. "On" was the reply. I crossed out the relevant "off", and wrote in "on", and asked him if it made sense now. He laughed when he realised he had read the piece three times and hadn't noticed.
Often, when we read or listen, we start to lose concentration, and our brains 'fill in' any information we don't pick up, by understanding what should be there. The other side of the coin is when we concentrate too much on the concept, and stop concentrating on what is being said or written. To see this is action, the next time you are in a restaurant, and the waiter asks in passing "Is everything alright?", answer in a pleasant tone of voice, "No, thank you, I'm not at all happy". Most probably, the waiter will smile, reply "That's fine", and walk off. Of course, this fact can be very useful at times.
The solution to this is quite easy, and is simply to ask the other person to repeat back what you have said, or to repeat what they have just said, in the form of a question. "So, if S=1, is the circuit off?" would be an example of checking to see that someone is listening to what they are saying. To check if the waiter was listening to you, the question might be "Is it fine that everything is not alright?"
The thing to remember, though, is this: If you're going to check that someone is paying attention, you had better be paying attention yourself!
