From Key Terms in Philosophy of Mind (Continuum, 2010):
extended mind, the hypothesis that mental states themselves, as opposed to the factors determining their CONTENT, extend beyond the physical boundaries of an organism to include environmental phenomena. The extended-mind hypothesis may thus be characterized as a kind of vehicle EXTERNALISM and contrasted against content externalism (see VEHICLE; CONTENT/VEHICLE DISTINCTION). A key argument for the extended-mind hypothesis advanced by Andy Clark and David CHALMERS involves a THOUGHT EXPERIMENT concerning two characters, Inga and Otto (their names are evocative of “inner” and “outer”), who both make their way to a museum they’ve been to previously. Otto’s “memory” of where the museum is located is not encoded in his nervous system (he’s imagined to be an Alzheimer’s patient with difficulty doing such a thing) but is instead written down in his notebook. Inga, however, has no external record of the location of the museum but remembers the location in the usual way of what we would consider her MEMORY, perhaps by accessing INFORMATION stored in her nervous system. Clark and Chalmers urge the conclusion that the distributed system that includes Otto’s brain and notebook counts as no less a SUPERVENIENCE base for a (vehicle of) BELIEF than does Inga’s purely (or, at least, more) internal system.