When the Brain Shapes Belief

"Picture two jurors sitting through the same trial. They listen to identical testimony, watch the same videos, and take notes on the same pieces of evidence. Yet by the end of the trial, they are more certain than ever that the other is wrong. One votes guilty, the other not guilty, and both are convinced their interpretation of the facts is the rational one. How can that be?"

"The brain is an efficient processor of information, but it operates under constraints. Neurons can only fire so much, and signals must reach a threshold before they trigger an action. These biological limits mean that the information we "see" is never a perfect reflection of what exists in the world; it is an interpreted, filtered version shaped by both our prior beliefs and our preferences."

"When new information arrives, it passes through this filtering system. The sensory system encodes the evidence, but before it becomes a decision, the brain compares it to a threshold that represents what we expect or value most. If the evidence is strong enough to surpass that threshold, we adjust our belief. If not, we tend to interpret it as consistent with what we already thought."

The brain processes information efficiently under biological constraints, causing it to filter rather than fully record sensory input. Neurons have limited firing capacity and decisions require signals to reach thresholds, so evidence is evaluated relative to expectations and values. Strong evidence that crosses these thresholds updates beliefs, but weaker signals are interpreted to fit prior beliefs and preferences. That adaptive filtering supports fast, energy-efficient decisions while producing confirmatory bias and divergent judgments among individuals exposed to identical information. Shared information can therefore widen disagreements because people encode and weigh identical facts differently, complicating efforts to reduce polarization.

Read at Psychology Today