Sleeper Effect

The sleeper effect refers to a psychological phenomenon wherein the persuasiveness of a message or information increases over time, even when the credibility of the source diminishes.


The sleeper effect occurs when individuals, after receiving a message, are initially influenced by the credibility of the source delivering the message. However, as time passes, people tend to forget the source but still retain the information. This results in a dissociation between the source of the message and the message content.


The sleeper effect can be attributed to various cognitive processes such as:

  • Decay Theory: The memory of the source weakens over time, leaving behind the impact of the message itself.
  • Discounting Cue: Individuals tend to discount or devalue the credibility of the source due to factors such as bias or ulterior motives.
  • Delayed Comparisons: People may fail to effectively compare the source with alternative sources, leading to a diminishing effect on credibility.


The sleeper effect has significant implications in various fields including advertising, persuasion techniques, and politics. Advertisers often employ this effect by using celebrities to promote products, knowing that the influence of the celebrity may fade, but the impact of the message will remain. In politics, negative messages or smear campaigns might be initially dismissed due to their questionable sources, but can eventually gain influence through the sleeper effect.