Sleeper effect

Biological Parallel

Animals initially discount information from unreliable sources but later recall the content while forgetting the source—message and messenger separate over time. Vervet monkeys learning alarm calls associate specific calls with threat types (eagle vs. leopard vs. snake), but over time remember the call-threat mapping while forgetting which individual first demonstrated it—the survival-critical content persists while social attribution fades. Capuchin monkeys observing tool use techniques retain the method but lose memory of which group member demonstrated it, treating learned behaviors as general knowledge rather than attributed inventions. Common ravens cache food after observing successful hiding techniques from experienced birds, but later retrieve using the learned strategy without recalling the specific demonstrator. The sleeper effect occurs because source memory decays faster than content: your brain prioritizes 'what was said' over 'who said it' for long-term storage. This is efficient compression: storing every message-source pair is expensive, so the brain keeps content and jettisons attribution.