Sentience is the ability to sense and experience the world, do you really need a study on a algorithm that predicts what words it should combine to create believable sentences to understand how it's not sentient? Let alone self aware or intelligent? It has no sensors to interact with the wider world or perceive it, no further computation of actually processing the information or learning from it. It just scrapes and parses data then stitches it together in a way that makes it read as human like....

Cite me a study that you have a brain, would be nice to have one, but it's not information that is needed by a person who understands the simplest of biology and thus is able to know that there is in fact a brain there.