A few years ago, I worked in a neuroimaging research lab and taught some basic Python programming to quite a few research assistants with psych degrees. At the time, a scientific computing or intro to programming course wasn't part of the psych curriculum at the university that the lab was. 0-indexed arrays were often a big sticking point. It just didn't mesh with their intuition.
For example, if `len(some_list)` returned 2, they would try to get the last value with `some_list[2]` and then get confused. Or for another example, if they used `for i in range(n)`, they'd be confused when `i` didn't start at 1 and end at n. They eventually caught on and learned further syntax such as `some_list[-1]` for getting the last value in a list. But, it was a bit of a frustrating experience for both them and myself because I only had time to teach them the basics and some google-fu as well as give them some example code. While 0-indexing was a source of a lot of their bugs in the beginning, I learned that the best method for them to get the hang of it was to encourage them to do a lot of print debugging, which was more than adequate for any scripts they'd be writing. They just really needed more feedback from what they wrote and what it actually did to get a better grasp of the idiosyncrasies of programming vs. their intuition.
Side note: The frustration of teaching non-techies Python was nothing compared to teaching them LaTeX. I was luckily able to eventually convince the PI to adopt Overleaf and organizing the text into separate files and using `\include` or `\input` to reduce the headache of collaborative writing as well as move all the internal docs to markdown. The latter became a huge help when we eventually moved to Jupyter notebooks for a lot of our python-related scripts as the team members already became adept enough with markdown. It was also easier to teach everyone how to use pandoc for making pretty PDFs of the internal docs or converting their markdown drafts into LaTeX.