RT Pramod¹, Samuel Hutchinson¹, Nancy Kanwisher; ¹MIT

Recent studies implicate regions of the human bilateral fronto-parietal cortices in intuitive physical reasoning—our ability to perceive, plan in, and predict the physical world. However, it remains unclear whether this "Physics Network" (PN) constitutes a distinct and domain-specific system, or whether instead it overlaps with the domain-general multiple demand (MD) network. To answer this question, we scanned subjects (N = 20) with fMRI in a pre-registered study and measured spatial overlap and resting-state correlation between the PN and MD networks. In each participant, the Physics Network was identified with our standard localizer contrasting a physical reasoning task on block tower stimuli (“Where will the block tower fall?”) with a color-based task (“Are there more blue or yellow blocks in the tower?”). The MD network was localized using a standard hard > easy spatial working memory task. We report three findings: (1) The overlap between the two networks was minimal, with an average Dice coefficient of 0.08. (2) Network-specific voxels exhibited consistent selectivity in held-out data. Voxels in the PN, identified using one half of the data, exhibited stronger physics > color task contrast in held-out data compared to the hard > easy spatial working memory contrast, and vice versa for the MD network (p < 0.0005 for network x localizer interaction in an ANOVA). (3) Resting-state functional correlation revealed that subregions within each network were more strongly correlated with each other than with subregions of the other network (average correlation: r = 0.49 within the PN, r = 0.51 within the MD network, and r = 0.29 between physics and MD networks). These findings indicate that the Physics Network is dissociable from the Multiple Demand system in both spatial location and resting functional time course, supporting its distinct role in intuitive physical reasoning.