I don't think eye tracking and do any good, because recognizing of familiar shapes and then mapping them to a familiar constructs and "structures" comes first.

So, reading a code with familiar shape is one thing (that why Lisp has such emphasis on the form of an expression, and Python put that into extreme), while reading long.chains.of.unfamiliar.methods.is.another.)

Then comes recognition of a familiar zones (areas) of an expression, expecting particular kind of sub-expressions here and there. Then match what you have seen with known whole things.

Lets say it is a recursive process of reduction to something already known by examining shapes, forms, and details.

So, shape matters. Small procedures, around ten lines matters. Naming matters, and, especially, using one-letter, non-confusing (no meaning) names for just a placeholders matters.

Let say that this solved in Lambda Calculus (by a naming strategy), and then in Lisp (by shapping strategy) by accident.)