Sleeper Effect

Definition

A sleeper effect in persuasion is a delayed increase in the impact of a persuasive message. In other words, a sleeper effect occurs when a communication shows no immediate persuasive effects, but, after some time, the recipient of the communication becomes more favorable toward the position advocated by the message. As a pattern of data, the sleeper effect is opposite to the typical finding that induced opinion change dissipates over time.

Discovery and Original Interpretation

The term sleeper effect was first used by Carl Hovland and his research associates to describe opinion change produced by the U.S. Army's Why We Fight films used to improve the morale of the troops during World War II. Specifically, Hovland found that the film The Battle of Britain increased U.S. Army recruits' confidence in their British allies when the effect of this film was assessed 9 weeks after it was shown (compared with an earlier assessment).

After the war, Hovland returned to his professorship at Yale University and conducted experiments on the sleeper effect to determine its underlying causes. According to Hovland, a sleeper effect occurs as a result of what he called the dissociation discounting cue hypothesis—in other words, a sleeper effect occurs when a persuasive message is presented with a discounting cue (such as a low-credible source or a counterargument). Just after receiving the message, the recipient recalls both message and discounting cue, resulting in little or no opinion change. After a delay, as the association between message and discounting cue weakens, the recipient may remember what was said without thinking about who said it.

History of Research

The Hovland research gave the sleeper effect scientific status as a replicable phenomenon and the dissociation discounting cue hypothesis credibility as the explanation for this phenomenon. As a result, the sleeper effect was discussed in almost every social psychology textbook of the 1950s and 1960s, appeared in related literatures (such as marketing, communications, public opinion, and sociology), and even obtained some popular notoriety as a lay idiom.

However, as the sleeper effect gained in notoriety, researchers found that it was difficult if not impossible to obtain and replicate the original Hovland findings. For example, Paulette Gillig and Tony Greenwald published a series of seven experiments that paired a persuasive message with a discounting cue. They were unable to find a sleeper effect. They were not the only ones unable to find a sleeper effect, prompting the question “Is it time to lay the sleeper effect to rest?”

The Differential Decay Hypothesis

Two sets of researchers working independently of each other were able to find reliable empirical conditions for producing a sleeper effect. In two sets of experiments conducted by Charles Gruder, Thomas Cook, and their colleagues and by Anthony Pratkanis, Greenwald, and their colleagues, reliable sleeper effects were obtained when (a) message recipients were induced to pay attention to message content by noting the important arguments in the message, (b) the discounting cue came after the message, and (c) message recipients rated the credibility of the message source immediately after receiving the message and cue. For example, in one experiment, participants underlined the important arguments as they read a persuasive message. After reading the message, subjects received a discounting cue stating that the message was false and then rated the trustworthiness of the message source. This set of procedures resulted in a sleeper effect.

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