History of the sleeper effect: Some logical pitfalls in accepting the null hypothesis

The history of research on the sleeper effect prior to 1978 can be divided into 5 stages: (a) initial discovery of the effect, (b) development of the underlying theory, (c) widespread acceptance of the effect and of the discounting cue explanation of it, (d) realization that past operational definitions of the effect were not isomorphic with the conceptual definition, and (e) repeated failure to demonstrate the effect once operational definitions were employed that corresponded to the conceptual definition (P. M. Gillig and A. G. Greenwald, 1974). These failures resulted in an invitation to accept the null hypothesis and to "lay sleeper effect to rest." This article illustrates why it is not justifiable to accept the null hypothesis about the sleeper effect. It is suggested that provisional acceptance of the null hypothesis depends on assuming that all the necessary theoretical, countervailing, statistical, and procedural conditions for an adequate test of the effect have been demonstrably met. It is further suggested that none of the empirical studies prior to 1978 demonstrably succeeded in meeting these conditions. However, adequate tests following the guidelines described by the authors for provisionally accepting the null hypothesis have recently been conducted, and the effect has been repeatedly found. A deductive model of the logical factors that should guide provisional acceptance of the null hypothesis is contrasted with a current model that stresses induction and statistical power analyses. (29 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved).