Sleeper Effect

When a message that initially carries little impact on an individual becomes stronger over time. This is opposite to the findings of most communications research, which suggest that the potency of a message decreases over time. It was first identified in 1949 by Carl Hovland, Lumsdaine, and Sheffield, when they looked at the effects of World War II propaganda films on army recruits. The sleeper effect occurs when there is a dissociation-discounting cue—for example, the message is presented by a nonreliable source, and so at first, the message is discounted. Over time, however, the message gains in potency as the message is dissociated from its source and the memory of the message does not decay as quickly as the memory of the source. For more information, see Hovland, Lumsdaine, and Sheffield (1949).