In this jointly authored book, Kirchhoff and Kiverstein defend the controversial thesis that phenomenal consciousness is realised by more than just the brain. They argue that the mechanisms and processes that realise phenomenal consciousness can at times extend across brain, body, and the social, material, and cultural world. Kirchhoff and Kiverstein offer a state-of-the-art tour of current arguments for and against extended consciousness. They aim to persuade you that it is possible to develop and defend the thesis of extended consciousness through the increasingly influential predictive processing theory developed in cognitive neuroscience. They show how predictive processing can be given a new reading as part of a third-wave account of the extended mind. The third-wave claims that the boundaries of mind are not fixed and stable but fragile and hard-won, and always open to negotiation. It calls into question any separation of the biological from the social and cultural when thinking about the boundaries of the mind. Kirchhoff and Kiverstein show how this account of the mind finds support in predictive processing, leading them to a view of phenomenal consciousness as partially realised by patterns of cultural practice.
Well worth a quick read if you are somewhat familiar with the consciousness literature. I learned about the three "waves" of extended cognition, what markov blankets are and how they are an interesting perspective/tool to look at organisms on different level.
It seems the main argument about extended consciousness is that the predictive processes that give rise to conscious experience are temporally and spatially distributed, and depend to a degree on culture and external experiences. It is quite straightforward to find mechanisms outside our bodies that contribute to the predictive processes, and not very easy to make a clear cut about where consciousness ends.
I find the argument presented in this book exciting, though not fully convincing.