Sleeper Effect

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.

Sleeper Effect Discovery and Original Interpretation

Sleeper EffectThe 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).

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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 the Sleeper Effect 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.

The procedures developed by these researchers are sufficiently different from those of earlier studies to warrant a new interpretation of the sleeper effect. As a replacement for the dissociation hypothesis, a differential decay interpretation was proposed that hypothesized a sleeper effect occurs when (a) the impact of the message decays more slowly than the impact of the discounting cue and (b) the information from the message and from the discounting cue is not immediately integrated to form an attitude (and thus the discounting cue is already dissociated from message content).

The procedures associated with a reliable sleeper effect and the differential decay hypothesis do not often occur in the real world. However, one case in which these conditions are met is when an advertisement makes a claim that is subsequently qualified or modified in a disclaimer (often given in small print and after the original message). In such cases, the disclaimer may not be well integrated with the original claim and thus its impact will decay quickly, resulting in the potential for a sleeper effect.

Other Sleeper Effects

Although much of the research on the sleeper effect has focused on the discounting cue manipulation, researchers have developed other procedures for producing sleeper effects including (a) delayed reaction to a fear-arousing message, (b) delayed insight into the implications of a message, (c) leveling and sharpening of a persuasive message over time, (d) dissipation of the effects of forewarning of persuasive intent, (e) group discussion of a message after a delay, (f) the dissipation of reactance induced by a message, (g) delayed internalization of the values of a message, (h) wearing-off of initial annoyance with a negative or tedious message, (i) delayed acceptance of an ego-attacking message, and (j) delayed impact of minority influence. Although these other procedures for obtaining a sleeper effect have been less well researched, they may indeed be more common in everyday life than are sleeper effects based on the differential decay hypothesis.


  1. Gillig, P. M., & Greenwald, A. G. (1974). Is it time to lay the sleeper effect to rest? Journal of Personality and Social Psychology, 29, 132-139.
  2. Gruder, C. L., Cook, T. D., Hennigan, K. M., Flay, B. R., Alessis, C., & Halamaj, J. (1978). Empirical tests of the absolute sleeper effect predicted from the discounting cue hypothesis. Journal of Personality and Social Psychology, 36, 1061-1074.
  3. Hovland, C. I., Janis, I. L., & Kelley, H. H. (1953). Communication and persuasion. New Haven, CT: Yale University Press.
  4. Pratkanis, A. R., Greenwald, A. G., Leippe, M. R., & Baumgardner, M. H. (1988). In search of reliable persuasion effects: III. The sleeper effect is dead. Long live the sleeper effect. Journal of Personality and Social Psychology, 54, 203-218.