Wheeler M (2019) Breaking the Waves: Beyond Parity and Complementarity in the Arguments for Extended Cognition. In: Colombo M, Irvine L & Stapleton M (eds.) Andy Clark and his Critics. Oxford: Oxford University Press, pp. 81-97. https://global.oup.com/academic/product/andy-clark-and-his-critics-9780190662813?cc=gb&lang=en&
First paragraph: According to the hypothesis of extended cognition (henceforth ExC), the physical machinery of mind sometimes extends beyond the skull and skin. More precisely, there are actual (in this world) cases of intelligent thought and action, in which the material vehicles that realize the thinking and thoughts concerned are spatially distributed over brain, body and world, in such a way that certain external (beyond-the-skin) elements (paradigmatically, technological devices) are rightly accorded fundamentally the same status (i.e., cognitive status) as would ordinarily be accorded to a subset of your neurons. So, if ExC is true, then sometimes your mobile phone isn’t just an external information storage device that saves your poor old brain the trouble of storing all those phone numbers (although it is that), it is also literally part of your memory, and thus part of your mind, in the sense that it’s part of your mnemonic machinery.