Anecdata: My high school got access to a computer (dialup modem). I essentially taught myself programming and then took the official class to teach me programming. Aced it, obviously. My younger sister saw how much I enjoyed programming so she took the class and struggled tremendously. I tutored her... I recall a problem where she had to do an operation repeatedly, an obvious (to me) application of a "for" loop. She struggled with why one problem pattern required a "for" loop and one pattern required an "if" statement.
My sister is very smart and was a straight "A" student in things that she could memorize, graduated from college summa cum laude (IIRC). She became a very good elementary school teacher. Myself, I was very much not an "A" student, especially in things that required me to memorize facts, but I "got" programming instantly.
More anecdata: I am now mentoring FIRST Robotics teams. I continue to see a dichotomy in aptitude for programming... two years ago I walked a student through a program for controlling a robot. She got pretty excited and interrupted my explanations and said "wait, let me think this through"... and she (verbally) worked out the logic of a complex "if" statement. She took over programming that year, is now in college pursuing a Computer Science major, and loving every minute of it.
Still more anecdata: Last year and this year I have a student that loves computers and intends to pursue it as a carrier, but he isn't a "natural." I spent a huge amount of time last year coaching him, but he still struggles to understand what pattern he is looking at and why e.g. he needs a "for" loop to solve the problem.
I could give a lot more anecdata, but I've worked with Robotics students that can program e.g. move sequences once I coached them through the details and I've worked with Robotics students that took off and created complex programs with nothing more than a simple introduction to constants, variables, loops, and conditional statements.