Readability and familiarity are not the same but closely related. There is nothing inherently more or less readable in the rust or haskell tree example.

I think there is work on "readability", just in another context: Its called typography and orthography. And I think the gist of it is: Do it like everybody else does, first and foremost, strange and unfamiliar equals unreadable.

> I think there is work on "readability", just in another context: Its called typography and orthography.

I think that's a very different case. Maybe some analogies might be drawn between some of that work and some of the lower-level aspects of reading code (related to syntax noise etc), but code readability, if it's a defensible concept at all, is a far more complex and layered phenomenon than letter & word recognition.

The first thing a researcher would need to establish is whether or not readability even exists as a natural kind apart from familiarity. I don't know the field, so this might already have been pursued somewhere.

> There's nothing unreadable [...] it's just unfamiliar if you don't know Rust

Agreed. Note the same applies to Haskell's syntax :)

People confuse "readable" with "based in my knowledge of Java and C, I can't make head or tails of this notation without reading a tutorial first", which in my opinion is not a sensible conclusion.

It's not entirely sensible, but it is understandable. I don't think most programmers are truly aware of how much they know, and how deeply automatic their recognition of programming constructs has become.