A few weeks ago, when I was reading something on my phone, Sean asked me what I was doing. "I'm reading", I said. "But you're not saying anything", said Sean. "I'm just saying it in my head when I'm reading". Since then he keeps asking me if I'm reading in my head.
So I asked him, "can you think in your head?". He got a look of intense concentration for about 20 seconds, kind of like constipation and finally said, "no". But he tried really hard!