Watch for
Finding yourself persuaded by something without remembering where you heard it.
Memory & AttentionBias #77
Sleeper Effect
Persuasion can increase as the source is forgotten.
A delayed increase in the persuasive impact of a message over time after the low-credibility source is forgotten while the message content remains accessible.
Why it matters: Important in advertising and propaganda. Explains why discredited information can still shape beliefs.
Try this
Evaluate the message and the source together when you first encounter them.
Real-world example
Remembering a product claim weeks later but forgetting it was made by a discredited spokesperson.
Key researchers
Carl Hovland, Irving Janis
First described in 1951
Psychological mechanism
Source-memory dissociation. The content and the credibility tag decay at different rates. If the content persists while the discounting cue fades the message gains retroactive persuasive power.
Seminal research
Carl I. Hovland, Irving L. Janis, and Harold H. Kelley (1953), "Communication and persuasion."
Below is a realistic scenario. Read it, then choose what you would do. The feedback will show whether a cognitive bias influenced your choice — not to judge, but to reveal the pattern in action.
Thought Experiment
This experiment places you in a realistic decision. Your instinctive choice will reveal whether bias is at work.
STEP 1 → ReadSTEP 2 → ChooseSTEP 3 → Reveal
Debrief
The sleeper effect shows that separating message from source over time gives low-credibility information retroactive power. The defence is to evaluate source and content simultaneously. If you find yourself persuaded by something check where it came from.