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Equation 3 · Part 1 · Ecological Rationality: When Biases Are Adaptations

Symbol c_fa

cfac_{fa}
cfac_{fa}

What this part means

the fitness cost of a false alarm.

Its job in the formula

cfc_fa is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.

Where the article explains it

Where cfac_{fa} is the fitness cost of a false alarm and cmissc_{miss} is the fitness cost of a miss, the threshold that minimizes total expected fitness cost is to infer H whenever:

The passage around this formula

This is a rule about optimal thresholds, not merely an intuition, and it has a compact formal statement. A decision-maker observes ambiguous evidence D bearing on whether a state H holds — a predator is present, a partner is unfaithful, an approach signals romantic interest — against the alternative that it does not. Where cfac_{fa} is the fitness cost of a false alarm and cmissc_{miss} is the fitness cost of a miss, the threshold that minimizes total expected fitness cost is to infer H whenever:

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Sources cited in the article section

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