Sleeper Effect

The sleeper effect is a psychological phenomenon whereby a highly persuasive message, paired with a discounting cue, causes an individual to be more persuaded by the message (rather than less persuaded) over time.

Figure A: Normal DecayFigure B: Sleeper Effect
When people are normally exposed to a highly persuasive message (such as an engaging or persuasive television ad), their attitudes toward the advocacy of the message display a significant increase. Over time, however, their newly formed attitudes seem to gravitate back toward the position held prior to receiving the message, almost as if they were never exposed to the communication in the first place. This pattern of normal decay in attitudes has been documented as the most frequently observed longitudinal pattern in persuasion research (Eagly & Chaiken, 1993). In contrast, some messages are often accompanied with a discounting cue (e.g., a message disclaimer, a low-credibility source) that would arouse a recipient’s suspicion of the validity of the message and suppress any attitude change that might occur with exposure to the message alone. Furthermore, when people are exposed to a persuasive message followed by a discounting cue, people tend to be more persuaded over time; this is referred to as the sleeper effect (Hovland & Weiss, 1951; Cook & Flay, 1978). For example, in political campaigns during important elections, undecided voters often see negative advertisements about a party or candidate running for office. At the end of the advertisement, they also might notice that the opposing candidate paid for the advertisement. Presumably, this would make voters question the truthfulness of the advertisement, and consequently, they may not be initially persuaded. However, even though the source of the advertisement lacked credibility, voters will be more likely to be persuaded later (and ultimately, vote against the candidate in the advertisement). This pattern of attitude change has puzzled social psychologists for nearly half a century, primarily due to its counter-intuitive nature and for its potential to aid in understanding attitude processes (Eagly & Chaiken, 1993). In addition, it has been the most widely studied phenomenon in persuasion research (Kumkale & Albarracín, 2004; see also Cook & Flay, 1978).

Source: Wikipedia