the measurement of the advertisement's attention-getting abilities and its relative persistence. These measures are obtained at relatively low costs.
After all these years of research, can we state when sleeper effects will occur? Many explanations of the sleeper effect have been proposed. Unfortunately, very few have been demonstrated to be reliable and the extent to which sleeper effects occur outside the laboratory has not been documented. A reliable sleeper effect has been obtained using operations suggested by the differential decay hypothesis. The specific operations used to produce a sleeper effect in the laboratory probably do not occur with any great frequency in natural settings. Given the pervasiveness of the decay of message impact, however, the differential decay of opposing persuasive materials can cause concern for attitude change agents.
The real value of laboratory research on the sleeper effect is not its production of a definitive interpretation of the real world, but its external invalidity. According to Mook ( 1983) it is often not the intention of laboratory research to describe the real world. "Artificial" findings are interesting because they demonstrate what can occur -- even if it rarely does. For example, there is no real world analog of a high energy physics experiment. Nevertheless, the study is valuable in what it teaches about the structure of atoms.
Given that a laboratory researcher has near unlimited control over the message recipient and situation, it is indeed amazing that there has been so much difficulty in producing a reliable sleeper effect. The use of externally invalid procedures further demonstrates the difficulty in overcoming the natural tendency for experimentally-induced opinion change to decay. Despite the difficulty, it is reassuring that persuasion theory and research have gained the sophistication to produce such an unwieldy effect as the sleeper effect in persuasion.
This research was supported by National Science Foundation Grants SOC 74-13436, BNS 76-11175, BNS 82-17006 and National Institute of Mental Health Grant MH 32317 all entitled Research in Persuasive Communications. Steven J. Breckler, Mahzarin R. Banaji, Andrew A. Mitchell, and Susan L. Schechtman provided valuable comments about the research.
Baumgardner, M. H. Leippe, M. R., Ronis, D. L., & Greenwald, A. G. ( 1983). In search of reliable persuasion effects: II. Associative learning and persistence of persuasion in a messagedense environment. Journal of Personality and Social Psychology, 45, 524-537.