How we change what others think, feel, believe and do
Make the subject believe that nobody cares about them.
Withhold letters and block all calls. Tell them that their friends have abandoned them. Say that nobody is trying to rescue them or get them released. Let them write letters and then withhold the replies so it looks as if nobody is interested in them.
Tell them that accomplices have been caught and have betrayed them. Use evidence that they do not know you have to add weight to this argument.
Have your colleagues be unkind and uncaring with them. They may either ignore them as if they are not there, or may be directly unpleasant. This is particularly usable when you have more than one interrogator. Guards should just be very distant (although the one friendly guard can also be a ploy).
With regard to yourself, there are two tactics. You can either be their only friend in the world, guiding them in what to do next (this is the most common ploy). Or you can pile on the pressure by being their worst oppressor.
You've got two brothers, haven't you. I would have thought they'd enquire about you, but nobody at all has called. Looks like they know you're in trouble and have abandoned you.
You know I hate working here. Nobody is very nice, are they? Why don't we just have a cup of coffee. I'll shut them out for a while.
Why are you protecting them? They have already told us that it was you who did it all.
We all have strong social needs including belonging and esteem. When people we think would care for us do not try to help us our self-esteem goes down as we suspect that their esteem of us is not as high as we thought it was.
When we find that our friends do not care, we feel rejected and that we no longer belong to their group. This may lead us to seek belonging elsewhere, which may include with the interrogator.