For that, you need Hilbert spaces, linear operators on them, a little spectral theory, …

Many people are trying to give a definitive answer, and there are good theories, but honestly, it is still very much an open question. There are multiple interpretations and as people tend to do in popular science, some spread their opinion as a fact, but we don’t have one correct answer.

The only thing I quickly found is this paper, which says that learning multiple things is not better nor worse than one thing at a time, but it also states in the abstract that cognitive psychologists believed up to that point that mixing multiple topics is beneficial.

That is actually not backed by science. Mixing material is a lot more effective than focusing on one thing.

It’s afro American sociolect.

Obviously, the apartment with the Confederate flag has a swastika inside.