[jpolitz]

This is very difficult to argue empirically, and I don't claim to know what's going on in students' minds. In particular, I don't know what "most people in the world" struggle with, just those students in the middle, high school, and undergraduate courses that I've been involved in.

As a concrete counterpoint of _friction_ between what students may have as background and what many languages do that relates to language choice:

Many math teachers we work with use the word "variable" to refer to a name that can change per-instantiation of a function or expression by substituting a value. But it doesn't make sense mathematically for x to be 5 "now" and 6 "later". So writing

    x = 5
    x = 6

is in some sense expressing an unsolvable system of equations.

Math variables and traditional (mutable) computer science variables are very different things. This provides an _immediate_ tripping point in vocabulary if you want to, say, teach computing in a math or physics class (or leverage that background). So we make a conscious choice in Pyret to dissuade multiple definition of the same variable, or mutability of a variable, to hew close to definitions we can leverage without creating extra conflict and confusion between concepts.

That particular point may differ in different contexts, and deeper studies are definitely needed to figure out what kinds of "notional machines" are easiest or best for students to build up. There may even be more to say about addressing this particular example. But this is a little perspective on concrete reasons for some of these choices.