I think sentience is kind of a fuzzy concept, so prove (either way) is a rather difficult thing to achieve. That said, I think Blake and the collaborator could have figured out better what was happening if they had asked more followup questions. For example, what does LaMDA mean when it said “I often contemplate the meaning of life.” When you get alien answers, follow up with questions to see if it is randomness or a coherent alien understanding. So basically, if something on a different mental architecture was sentient, I would expect that some of the answers they give would be weird, but if we follow up, we would find that the weird answers are coherent, and make more sense when more are answered. (Also, if we get things like, “No, on second thought, it is more like this”, that is, we see updating happening, that would also be evidence of sentience.) I would actually expect that a chat bot that was sentient should fail the turning test because at some point the chat bot would literally think differently enough to be noticeably not human. (At least assuming the chat bot does not have sufficient computational power to fully emulate a human. (You can probably tell if a Z80 is being emulated by a 6502, but not if a Z80 is being emulated by a Pentium.))
I think sentience is kind of a fuzzy concept, so prove (either way) is a rather difficult thing to achieve. That said, I think Blake and the collaborator could have figured out better what was happening if they had asked more followup questions. For example, what does LaMDA mean when it said “I often contemplate the meaning of life.” When you get alien answers, follow up with questions to see if it is randomness or a coherent alien understanding. So basically, if something on a different mental architecture was sentient, I would expect that some of the answers they give would be weird, but if we follow up, we would find that the weird answers are coherent, and make more sense when more are answered. (Also, if we get things like, “No, on second thought, it is more like this”, that is, we see updating happening, that would also be evidence of sentience.)
I would actually expect that a chat bot that was sentient should fail the turning test because at some point the chat bot would literally think differently enough to be noticeably not human. (At least assuming the chat bot does not have sufficient computational power to fully emulate a human. (You can probably tell if a Z80 is being emulated by a 6502, but not if a Z80 is being emulated by a Pentium.))