Controlling for Transient Motivation in Cognitive Manipulation Studies

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Abstract
The four types of control groups commonly employed in cognitive manipulation studies were identified and arguments were presented concerning the problematic nature of each group as a baseline for identifying the “true” treatment effect. A general, two-step control procedure was advocated in which the researcher first identifies the most appropriate control group for a given context and then supplements this experimental control with statistical control. In reference to the latter controls, procedures were presented for developing a task-specific index as a covariable to be employed with a suitable measure of verbal aptitude in an analysis of covariance. The procedure was demonstrated on data from a quasi-experimental design in which it was shown that three different conclusions were possible depending upon the control procedures employed. It was argued that the converging operations obtained from the multivariate approach to the data analyses supported the results from the two-step control procedure. This procedure is not presented as a panacea but represents an attempt to “go beyond” the mechanical appocation of typical experimental controls for placebo effects.