Almost every day we show a two-minute children's video to all three children, then ask a question about it. The question is usually relatively simple as it involves recall of a fact, and does not require analysis or even comprehension.
Yesterday we ask our almost 7 year-old son the question, and he gives a completely irrelevant answer from a completely different part of the video. We tell him that's incorrect.
We ask his little sister the exact same question. Sometimes she knows, sometimes she doesn't know, and sometimes we suspect she pretends to not know because she finds it cute and fun. However, she is four years old, so this is a learning experience for her, not something we expect her to already be able to do.
We ask his big sister who is mentally 3 years old because of cerebral palsy the exact same question. Sometimes she surprises us by knowing. This time she thinks it's a game to not know because of her siblings' responses. I whisper the answer to her and she gives it.
I ask the four year-old sister the question again and she answers correctly this time, having heard her sister give the correct answer after I whispered it to her.
I ask our son the question again, who was quiet and looking directly at his sisters when they each gave the correct answer to the exact same question. He gives the exact same off-the-wall answer he tried to give before!
We know from previous experience that he will usually get stuck on that answer. We can repeat the cycle a few more times and he will give the same answer, so now we just give up and try it again tomorrow. We think he is so focused on trying to give the right answer that he is thinking about his best guess for it, and forgets to listen to what's going on around him, even though outwardly he appears to be paying close attention.
This happens two or three times per week, and what also has us concerned is that sometimes he may not really understand a correct answer he gives, but just got lucky at guessing which random phrase we will ask about.
So my questions are how can we tell when he is really paying attention and when he is just making lucky guesses or copying others, and how can we help him snap out of these inward cycles? Is there a name for this kind of behavior that I can use to research it further?