I do think AI could be a better language tutor than an average language teacher, but I don't think Duolingo's approach is very effective.
The ideal AI-powered tutor would work more closely to a private language tutor. It would speak with you and gradually integrating language concepts into the conversation. When you make mistakes, it could correct you on the spot and keep track of where your strengths and weaknesses are.
You should look at HelloTalk. It's real people communicating in each others' language. Unbelievably great service, almost as good as sitting down to a coffee with someone.
Actually, in some ways better. HelloTalk has a "correct the other person's sentence" feature that shows an inline diff, yet it's simple enough for people who have never heard the term diff.
Correction is not always desirable. The goal in learning a language is rarely to be grammatically "correct" in the language, but rather to communicate. And communication doesn't need perfect grammar.
When I was working as language teacher, I was tasked specifically with teaching speaking. I would often use information gap activities. These are activities where two or more parties have pieces of information but need to obtain pieces from others in order to complete the task. Sometimes, these would us language forms (re: sentence structures), but most of the time they were free flow activities. It didn't matter how "correct" the language was so long as the idea was communicated.
To think about it another, how often do we make mistakes when speaking? Writing? And yet, we still managed to communicate just fine.
That's not to say there shouldn't be any focus on form, but simply that it's not nearly as important as many tend to think when it comes to language learning.
A lot people on HN got their early programming chops from Stack Overflow and spotty internet tutorials, and have made the mistake of thinking that everything else can also be learned this way.
I'm neither, but I tried learning Spanish from a "language teacher" and it didn't work. I'm not alone. I've spoke to dozens who had the same experience.
Years later I learned from people with the same method I described.
The AI models (large LANGUAGE models) of today seem very close to replicating that experience.
Try telling ChatGPT with voice mode "let us talk about X in [pick language]... Correct me when I'm wrong and explain why".
I'm curious where you think it's failing.
What do you feel is missing to replicate a good language teacher?
The ideal AI-powered tutor would work more closely to a private language tutor. It would speak with you and gradually integrating language concepts into the conversation. When you make mistakes, it could correct you on the spot and keep track of where your strengths and weaknesses are.