But I suspect your notion of understanding is not measurable, is it? For you, chatGPT lacks something essential such that it is incapable of understanding, no matter the test. Or do you have a way to measure this without appeal to consciousness or essentialism?
Does understanding require consciousness? Maybe yes, for the kind of understanding I'm thinking of, but I'm not certain of that.
How do you measure understanding? You step a bit outside the training set, and see if whoever (or whatever) being tested can apply what it has learned in that somewhat novel situation. That's hard when ChatGPT has been trained on the entire internet. But to the degree we can test it, ChatGPT often falls down horribly. (It even falls down on things that should be within its training set.) So we conclude that it doesn't actually understand.
How come humans are so efficient when these computers are using enormous amounts of energy? When will we have a computer that only requires a few slices of pizza worth of energy to get to the next step?
I don't think this is the case at all. Language is how we encode and communicate ideas/concepts/practicalities; with sufficient data, the links are extractable just from the text.
What GPT does is not "text" - although it centers that as the interface - but "symbols". The billions of parameters express different syntaxes and how they relate to each other. That's why GPT can translate languages and explain things using different words or as different personas.
So when we ask it to solve a spatial problem, we aren't getting a result based on muscle memory and visual estimation like "oh, it's about 1/3rd of the way down the number line". Instead, GPT has devised some internal syntax that frames a spatial problem in symbolic terms. It doesn't use words as we know them to achieve the solution, but has grasped some deeper underlying symbolic pattern in how we talk about a subject like a physics problem.
And this often works! But it also accounts for why its mathematical reasoning is limited in seemingly elementary ways and it quickly deviates into an illogical solution, because it is drawing on an alien means of "intuiting" answers.
We can definitely call it intelligent in some ways, but not in the same ways we are.
To the extent that humans have encoded the concepts into words, and that text is in the training set, to that degree ChatGPT can work with the words in a way that is at least somewhat true to the concepts encoded in them. But it doesn't actually understand any of the concepts - just words and their relationships.