Sensitivity and specificity

Sensitivity asks: when the thing you are looking for is really there, does your test find it? Specificity asks: when your test says it found something, is it really the thing you were looking for — or could it be anyone's?

A good detector is both sensitive (it catches what is there) and specific (what it catches is the right thing). But the two often trade off: raising sensitivity (cast a wider net) lowers specificity (more false positives), and raising specificity (tighten the net) lowers sensitivity (more misses). The trade-off is the shape of every detection problem, from medical screening to copyright canaries.

In the castle's canary wing, the trade-off runs through the detection-entitlement split. A conventional binding form (conjunction, lexical cohesion) is high-sensitivity — the tail follows the hook reliably because everyone uses the form — but low-specificity, because the tail could be anyone's tail. A coined term or a rich first-definition is high-specificity — the distinctive phrasing points to one hook — but low-sensitivity, because the distinctiveness makes it harder to extract and less likely to be reproduced verbatim. The hybrid canary splits the trade-off across two sentences: a conventional hook for sensitivity, a distinctive tail for specificity.

Links

canary-trap · entitlement · cohesion