I don’t have aphantasia but learning about it made me reflect on the way my perception and mental processes work.
For me it’s all about feelings. I spend lots of time asking myself why I’m feeling the way I do and which feelings contribute to an emotion. For example when I’m feeling not well l really try hard to find the cause – like is it anger, frustration, sadness, fear, uncertainty, loneliness, boredom… (mostly it’s a combination)
Those feelings are to me the building blocks of emotions and by taking my own emotions apart I kind of started recognising some patterns in the behaviour of others. E.g. if someone yells at me I start thinking: That might not be agression but uncertainty.
It is like the feelings are the pieces of a mosaic. The smaller the pieces the better you can recreate your representation of something you see in someone else.
Your description is very interesting as it seems that you have the mosaic pieces and are able to create complex emotions with them for fictional characters but it is hard for you to do the same with actual people.
A difference could be that with fictional characters you might get a description of their feelings (like in books you find detailed descriptions of the thoughts and feelings of a character). In real life it is more like guesswork and depends on intuition. There is a lot of uncertainty involved and it might be stressful to react to a real situation. You might misjudge the situation or get it right but the other one doesn’t like your reaction. So many things could go wrong!
It would be interesting to find out if it it is perception (not knowing what the other feels) or stress/uncertainty that prevents you from expressing empathy.
If it’s the latter, I found out that people are in general more tolerant towards our actions than we think. If we get it wrong, we get the chance to explain our own uncertainty and no damage is done. This allowes me to experiment with different reactions, get more insights and improve…