Donald Trump can change the temperature of a room with a sentence. One minute he is certain, the next he is backtracking. One day he is threatening, the next he is hinting at a deal. Even before anything concrete happens, people brace for his next turn.

That reaction is not just political. It is what unpredictability does to any system that requires stability. To act at all, you need some working sense of what is happening and what is likely to happen next.

One influential framework in brain science called predictive processing suggests the mind does not wait passively for events. It constantly guesses what will happen, checks those guesses against reality, and adjusts.

A brain that predicts can prepare, even when what it prepares for is uncertainty. The gap between what you expect and what actually happens is known as a prediction error. These gaps are not mistakes but the basis of learning. When they resolve, the brain updates its picture of the world and moves on.

This is not about what anyone intends, but about what unpredictability does to systems that need some stability to work. Trouble starts when mismatches do not resolve because the source keeps changing. People are told one thing,........

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