Anthony R. Pratkanis
Carnegie-Mellon University

Anthony G. Greenwald
Ohio State University

Attitude change agents are often concerned about the fruits of their labor
after the passage of time. A government agency charged with litter control
hopes that its anti-litter campaign will be effective long after its leaflets have
been discarded. An advertiser hopes that the impact of a TV commercial per-
sists through the interval between presentation and subsequent shopping
trip. The pulpit preacher seeks a conviction of everlasting salvation and, not
just momentary bliss from the congregation.

For the most part, research on persuasion finds that whenever opinion
change occurs, it usually dissipates over time (see Cook & Flay, 1978 for a re-
view). Over 50 years ago, researchers found a pattern of data opposite to this
typical trend. This chapter tells the story of the history of this effect -- termed
the sleeper effect in persuasion.

In 1928 the Motion Picture Research Council commissioned a series of stud-
ies to investigate the effects of motion pictures on children. Peterson and
Thurstone ( 1933) took up their charge by showing films about the Germans,
gambling, prohibition, and other social issues to school children living in the
midwest. They found that many of the films did indeed change children's at-
titudes with effects diminishing slightly over time. However, a pro-German

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