Earnings surprise moves stocks through the same equation that fires dopamine neurons in monkey midbrain.

Schultz, Dayan, and Montague showed in 1997 that dopamine neurons fire in response to reward minus expected reward, not in response to reward. A monkey that expects juice and gets juice produces no dopamine spike. A monkey that expects nothing and gets juice produces a large spike. A monkey that expects juice and gets nothing produces a dip below baseline.

Equity markets compute the same quantity in aggregate. A company that earns $1.00 against a $1.00 consensus moves little. The same company earning $1.00 against a $0.50 consensus moves up sharply. The same company earning $1.00 against a $1.50 consensus moves down sharply. Same fundamentals, three different prices.

The match is at the equation level. Both systems compute realized minus expected and use the result to update future expectations. The TD learning update rule that describes dopamine firing also describes how analysts revise forecasts after surprise.

The operational implication: in liquid markets, alpha lives in the prediction error, not in the realized number. The fundamentals are priced. The deviation from expected fundamentals is not.