Mechanical and semantic knowledge mediate the implicit understanding of the physical world

Most recent accounts highlight the importance of two aspects of cognition in the implicit understanding of the physical world: semantic knowledge (the ability to recognize, categorize, and relate concepts) and mechanical knowledge (the capability to comprehend how things mechanically work). However, how the human brain may integrate these cognitive processes remains largely unexplored. Here, we use functional magnetic resonance imaging to investigate this integration employing a novel free-viewing task. Participants viewed images depicting object-tool pairs that were either mechanically consistent (e.g., nail - steel hammer) or mechanically inconsistent (e.g., scarf - steel hammer). These pairs were situated on a metal plate atop a table, with a stripped electrical cable in contact with the plate that could be plugged in or out from the electrical line, rendering the tools either electrified or not. Task-based functional connectivity revealed an interplay among specific left-brain regions - the middle temporal (MTG), inferior frontal (IFG), and supramarginal (SMG) gyri - during the processing of mechanical actions and physics principles, associating the activity of these areas with mechanical knowledge (SMG) and object-related semantic knowledge (MTG). Notably, the IFG was active during both types of processing, suggesting a critical role of this region in multi-modal information integration. These findings support the most recent integrated neurocognitive models of physical understanding, deepening our comprehension of how we make sense of the physical world.