Sleeper Effect

Persuasion from a source we initially distrust has low immediate impact — but grows over time, because we forget the unreliable source while retaining the message.

• WWII propaganda films shown to American soldiers had little initial effect on attitudes, but produced measurable shifts weeks later — the 'enemy source' label faded faster than the content.
• A tabloid's misleading health scare is immediately discounted by most readers — but the claim persists in memory long after the dubious source is forgotten.
• Advertising from an unknown brand is dismissed at first exposure but builds recall and credibility through repetition, as the 'unfamiliar brand' tag fades.