I had a relative who used to do this. She had a personality disorder (genuine diagnosis) and only saw people as for her “use”, she hated any idea that her “loved ones” world might not revolve around her. We all had to walk on eggshells around her and if we were quiet she’d want to know what we’d been thinking about and then ask if we were telling the truth.
She stopped asking me after my replies were the following;
“You look very preoccupied. What are you thinking about?”
“I’m thinking about how long my tampon has been in. I accidentally left it in for three hours longer than I should have when I was on my last period and then I got a nasty infection and I’m sure it might have been to do with that, you know I have a very heavy flow and it can’t be good to have something like that in there for too long. The smell was awful. I consider myself to have had a very lucky escape. I worry that I could have got toxic shock syndrome. You know when I think about it, I wonder if tampons are even all that good for you. When I was in California, they had tampons made of organic cotton. Cotton can be toxic I think. I hope there aren’t any long term repercussions. I did think of getting a mooncup but then I’m quite small down there and I’m not sure what size to go for...I take it you’ve heard of mooncups? Oh you haven’t, wait, let me Google and I’ll show you!”
“You look puzzled. What are you thinking about?”
(She was really not academic)
“Do you ever realise that you’ve suddenly forgotten something that you used to be really good at? Just now...it sort of popped into my head that I have completely forgotten how to do Quadratic Equations. I’m trying to remember when I forgot how to do them. I feel like this time last year I could have quite confidently have done a few without even blinking but now...all of a sudden...it’s gone. And yet, for years...I could do them. Gosh! I think I’ve even forgotten very basic trigonometry. Is it possible that, whilst studying for my GSCE’s, with the scope and breadth of everything that we were studying all at once, that I never actually committed basic algebra to my long term memory? Maybe it all went into short term memory? I wonder how long things stay in our short term memories? Is there an expiry date do you think? When exactly does it get...pushed out? Gosh...don’t you think that this sort of thing is completely FASCINATING?! I do. I could talk about it for DAYS!”
The one that really upset her was,
“You’ll maybe know the answer to this seeing as you are Catholic! I’m thinking about the Creed. You know where is says “I look forward to the resurrection of the dead and the life of the world to come?” Where are the dead now? Like right this moment. So the people that have been dead for thousands of years? Are they not resurrected yet? Do they have an awareness of the fact that they are dead but not resurrected? I’ve heard that the resurrection of the dead is when souls are reunited with their earthly bodies so does that mean that right now those souls are wandering around without an body and, if so, where are their bodies right now? And do you get to choose the age of the body you have when you are fully resurrected? I’ve heard theologians say that God’s time is not like our time and that it’s not linear or that what for us is a thousand years is like, a second for God, so when we die are we on God’s time...like when we change time zones on holiday? Or are we on human time until the “resurrection of the dead”. I just worry about wandering about in limbo, a soul without a body for...twenty thousand years or something, just waiting for the resurrection of the dead. I do hope we end up on God’s time and it’s more like a second because doesn’t the alternative just send shivers up and down your spine and fill you with absolute dread and fear?”
After that she never asked me what I was thinking again 
.