This one's not too tough. Even our narrator knows he's detached:
These are some of my Behavioural Problems
A. Not talking to people for a long time [...]
K. Not noticing that people are angry with me. (73.2)
He doesn't like "chatting" or talking to people in general, and he hates being touched. He can't identify emotions in others, and has trouble recognizing them in himself. So it's no wonder that his attitude toward everything is pretty distant.
Take a look at this passage:
Father was standing in the corridor. He held up his right hand and spread his fingers out in a fan. I held up my left hand and spread my fingers out in a fan and we made our fingers and thumbs touch each other. We do this because sometimes Father wants to give me a hug, but I do not like hugging people, so we do this instead, and it means that he loves me. (31.5)
This is an incredibly sweet moment, we think. But we get the feeling that Christopher doesn't get that it's sweet. The subtle difference between "we do this instead, because he loves me" (not his words) and "we do this instead, and it means that he loves me" (his words) actually reveals massive difference in tone. He knows what things mean (that's why he's so good with logic), but he just doesn't feel them.