When persuasion grows stronger over time
Common sense says persuasion should fade over time. You hear an argument, you're convinced, then you gradually forget and return to your original position. Right?
Wrong. The sleeper effect is a remarkable phenomenon where persuasion actually increases over time—but only when the message comes from a source you initially distrust.
You dismiss the message because of the sketchy source. But weeks later, you remember what was said while forgetting who said it. The discounting cue fades faster than the message itself.
In 1949, psychologist Carl Hovland was studying U.S. Army propaganda films called "Why We Fight." He measured soldiers' attitudes toward Britain after watching "The Battle of Britain."
5 days later: No measurable attitude change. The film seemed ineffective.
9 weeks later: Significant positive shift toward Britain!
The film had worked—it just needed time to "wake up." Thus, the sleeper effect was born.
Read a persuasive message and its source. Rate how much you believe it. Then we'll simulate time passing and test what you remember.
The message and the source are stored separately in memory. Over time, the association between them weakens. You remember what was said but forget who said it. Without the "discounting cue" (the sketchy source), the message stands on its own merits—and becomes more persuasive.