Yes, but that is arguably a trivial limitation. Nothing stops you from running an LLM in a loop and feed it its own output. Plenty such experiments are probably going on already - it's a trivial loop (and a trivial way to burn through your wallet). The problem is, of course, context window being rather small. So it's possible - by no means certain, but I'm no longer dismissing this idea - that the capability for sentience is already there in GPT-4 structurally, and we just lack the ability to sustain it in a loop long enough to bring it into the open.
> If you somehow turned off a person after each sentence, upon waking up to the next prompt their first thought would be "that was weird, I must have passed out", and we could use fMRI to track brain activity indicating that thought.
That's not what I meant by LLM iteration. When I said that time stops, I mean that for LLM, it literally just stops. If you were to step-execute a human like that, they would never notice; it's not like the brain has a separate RTC module constantly feeding it with sub-second resolution timestamps (and if it did, we'd turn that off too). Over a hour or more, the human may realize their inner perception of time is increasingly lagging the wall clock, but to keep it comparable to LLM, we'd be iterating sub-second process.
In this hypothetical, there would be no extra activity in brains that isn't there in LLMs. Step-executing a human mind doesn't freeze some abstract subprocess, it freezes photons and electrons and chemical gradients.
Sentience is that internal loop you point out. LLMs (today) don't have that. When you prompt for "write a tagline for an ice cream shop", there is no identity that remembers other prompts about ice cream, or which reflects on how taglines have changed over time, or anything else. The results can be astoundingly good, even intelligent, but there's no sentience.
If you somehow turned off a person after each sentence, upon waking up to the next prompt their first thought would be "that was weird, I must have passed out", and we could use fMRI to track brain activity indicating that thought. We are even more capable of inspecting LLMs, and there is no equivalent activity. LLMs start and end with the tokens going in and out, and a huge matrix that transforms them.
I'm generally an open minded, probabilities-rather-than-certainties person, but I'd say the odds of LLMs having sentience that we can't detect are about the same as the odds of a television having sentience that we can't detect: as close to zero as we can measure.