Probably a combination of environment (nurture) and simple evolution. The brain is a complex computer that handles a metric-fuck-ton of information. Some minor variation in how that information is processed or accessed is bound to develope, especially when the sample size is in the billions.

I don’t think issues is a great word for something that doesn’t have an obvious negative outcome.

I have an inner monologue that is something like an auditory version of my thoughts. Reminds me of a movie narrator explaining what people arre thinking, but not a verbal exchange like the article describes. It is absolutely zero help in remembering things because it switches to my current thoughts, and doesn’t just run in the background. It doesn’t seem to be a negative at all, and it is hearing hearing what I’m thinking but not rrally hearing because it doesn’t sound like anyone in particular.

On the visual side, I can’t picture something I haven’t seen before and only have brief flashes of what I have seen before. Can’t picture anything in my mind except the vaguest of stereotypical ideas, like a tropical island is a tiny island with a palm tree or a lagoon. Maybe the rough outline of a mountain peak. Can’t draw anything like that from imagination, but can do a pretty solid sketch of something that I have a visual reference for. Also not really an issue, since most things don’t require picturing them without seeing them, but it did derail my interest in art and I can’t do any of the meditation exercises that involve picturing myself somewhere.

I assume any of these kinds of differences can be caused by a combination of genetics and environment since genes are expressed differently based on experience and environments can also impact people in ways that don’t involve genes.