The sleeper effect identified by psychologist Carl Hovland refers to the "hidden" effect of a propaganda message even when it comes from a discredible source.

Hovland studied the effects of the Frank Capra World War II propaganda film Why We Fight on US soldiers. He found that when the soldiers found the source of a piece of information discredible, they would discount it. However, after an amount of time soldiers would forget where a given message originated, but they would still remember the message itself. In this way, information from a low credibility source could increase in effectiveness.

In one experiment, students read arguments about nuclear power. One group was told the arguments came from an American nuclear scientist, and the other was told that they came from the Soviet newspaper Pravda. Only the first group showed attitude change in the short term. After several weeks, once the supposed sources of the information had been forgotten, both groups showed the same degree of attitude change.

The effect has since been confirmed by other studies.

See also: mere exposure effect.

References

• Hovland, C. I., Lumsdaine, A. & Sheffield, F. (1949). Experiments on mass communication. Princeton, NJ: Princeton University Press.
• Hovland, C. I., Janis, I. L. & Kelley, H. H. (1953). Communications and persuasion: Psychological studies in opinion change. New Haven, CT: Yale University Press

External links

• Changingminds.org: sleeper effect