Déjà vu

Biological Parallel

Pattern-matching systems must trade speed against accuracy, and occasionally fire prematurely. Prey animals like rabbits and deer trigger flight responses to partial predator cues—a glimpsed movement, a specific shape—rather than waiting for confirmation. This false-positive bias (run from shadows that might be predators) outperforms false-negative bias (wait for certainty) in survival terms. The familiarity-detection circuit operates similarly: neural recognition systems signal 'known pattern' based on partial matches because waiting for complete verification in ancestral environments meant delayed responses to threats or opportunities. Déjà vu is the subjective experience of this prediction machinery misfiring—the brain signals 'I've seen this' before completing verification. Across mammals, the cost of occasional false recognition is far lower than the cost of delayed recognition.