We used a semantic feature matching task combined with multivoxel pattern decoding to test contrasting accounts of the role of the default mode network (DMN) in cognitive flexibility. By one view, DMN and multiple-demand cortex have opposing roles in cognition – with DMN and multiple-demand regions within the dorsal attention network (DAN) supporting internal and external cognition respectively. Consequently, while multiple-demand regions can decode current goal information, semantically-relevant DMN regions might decode conceptual similarity irrespective of task demands. Alternatively, DMN regions, like multiple-demand cortex, might show sensitivity to changing task demands, since both networks dynamically alter their patterns of connectivity depending on the context. Our task required human participants (any gender) to integrate conceptual knowledge with changing task goals, such that successive decisions were based on different features of the items (colour, shape and size). This allowed us to simultane...