Brain Region Analysis — Real vs. Reversed Physics

This is the dominant real-physics-predictive region. The anterior and mid-cingulate cortex (ACC/MCC) functions as a forward model that predicts future states (Alexander & Brown, 2019). Limongi et al. (2013) showed that temporal prediction errors — the discrepancy between when an event was expected to occur and when it actually occurred — modulate coupling between the cingulate and insula. For real physics videos, the cingulate can successfully build a forward model: a ball falls, accelerates under gravity, bounces. In reversed videos, the forward model breaks down — objects spontaneously launch upward, fluids reassemble — which is why the cingulate activates more for real physics where predictions are coherent and sustained.

Part of the mPFC, involved in predictive coding and maintaining internal models. Fischer et al. (2016) identified a network including premotor cortex and supplementary motor area that activates during intuitive physical reasoning. The mPFC likely supports high-level prediction and model-updating when watching coherent physical scenes.

The posterior lateral fissure borders the superior temporal gyrus and the inferior parietal lobule, near the temporoparietal junction. This region is adjacent to motion-sensitive areas (MT+/V5) and areas involved in event structure processing. It would process the temporal dynamics and causal structure of physical events — when objects move in physically consistent ways, this region can extract meaningful event structure.

These temporal regions are involved in higher-order visual processing, including motion perception, object recognition, and event structure. The middle temporal gyrus (near MT+/V5) specifically processes visual motion. Real physics videos have coherent, physically plausible motion patterns that this region would process more efficiently.

This is perhaps the most important finding. Schwettmann et al. (2019) showed that dorsal fronto-parietal cortex — including the IPS — encodes invariant representations of physical variables like mass, generalizing across different scenarios, materials, and motion patterns. Fischer et al. (2016) identified a broader "physics engine" network (primarily premotor cortex and supplementary motor area) that activates during intuitive physical reasoning. The IPS is part of this extended network. Here, the IPS predicts reversed physics. This is counterintuitive at first, but has a compelling explanation: when watching reversed videos, the brain's physics engine detects violations — objects moving in physically impossible ways — and activates more intensely as it tries to reconcile the visual input with its internal physical model. This is consistent with prediction error theory.

The insula is the brain's primary salience and prediction error hub. The anterior insula encodes risk prediction errors (Bossaerts, 2010) and signals deviations from expectations via bursts of beta oscillations (Haufler et al., 2022). Limongi et al. (2013) showed that temporal prediction errors specifically modulate cingulate-insular coupling. Reversed physics videos represent massive violations of temporal and physical expectations. Objects move at the wrong times, in the wrong directions, with impossible causal sequences.

The parahippocampal gyrus encodes spatial layout and contextual associations (Epstein & Kanwisher, 1998). Research shows it is primarily engaged when processing scenes and spatial context — it responds strongly to congruent, meaningful scene contexts. Our interpretation is that reversed physics videos disrupt normal contextual processing: objects appear in impossible spatial configurations (liquid flying upward, objects launching off surfaces), which would alter the parahippocampal response compared to normal physics. However, calling it a "violation detector" would be an overstatement — its established function is encoding contextual associations, not detecting violations per se.

Part of the temporoparietal junction (TPJ), the supramarginal gyrus is involved in temporal order judgments. Davis, Christie & Rorden (2009) showed that the TPJ activates specifically when making judgments about the temporal order of events. Reversed videos inherently violate temporal order — events happen backward — which would specifically engage this temporal-order processing region.

The frontopolar cortex (Brodmann area 10) is involved in monitoring and evaluating competing cognitive representations. When watching reversed physics, the brain simultaneously processes the visual input (what it sees) and the expected physics (what should happen), creating a conflict that engages the frontopolar cortex's conflict-monitoring function.