The effect of knowledge of missing an experimental treatment on behaviour

Walther, Barnabas Joseph (1981) The effect of knowledge of missing an experimental treatment on behaviour. Masters thesis, Memorial University of Newfoundland.

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Abstract

The research examined how individuals react when they know they are missing an experimental treatment as a function of assignment to a control group and considered whether these reactions could produce treatment effects. There were three experimental conditions. Subjects in one condition were informed that they were a control group and unlike the experimental group would not receive extra money for doing well on experimental tasks. Subjects in a second condition were informed that they were in a control group and unlike the experimental group would not receive electric shocks for poor performance on experimental tasks. In the third condition subjects were given no information concerning the existence of any other condition. Dependent measures included task performance and measures of attitudes toward the experiment. Subjects who believed they were missing a positive treatment tended to be less careful, make more errors, and do less work than subjects unaware of any other condition. Subjects who believed they were missing a negative treatment tended to be more careful, make fewer errors, and do more work than individuals unaware of any other condition. Apparently, knowledge of missing either a positive or negative experimental treatment does affect behaviour. There were no differences in attitude towards the experiment as a function of experimental condition. These significant differences in task performance were discussed in terms of various social psychological theories, the evaluation of social programs, and Campbell's suggestion of "informed randomization”.

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