The purpose of the present work was to identify some of the factors that influence effectiveness of warnings. Two laboratory experiments designed to examine behavioral effectiveness indicated that a warning placed before procedural instructions is more likely to lead to compliance than a warning that follows instructions. Two rating experiments indicated that for greatest perceived effectiveness, environmental warnings generally require a signal word plus hazard, consequence, and instruction statements. A third rating experiment suggested that informative, nonredundant statements add to a warning's perceived effectiveness. Several field demonstration studies showed that cost of compliance and salience influence behavioral effectiveness. Implications and applications to warning design are discussed.

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In order to generalize the results of an experiment beyond the specific stimuli employed, it is necessary to consider variance due to stimulus sampling. This can be accomplished by treating stimuli as a random effect rather than the traditional procedure of treating stimuli as a fixed effect. The serious consequences of the traditional approach are illustrated using examples from applied psychology. Statistical and design considerations for generalizing the results of experiments are discussed.

A paradigm was developed to examine the effectiveness of warnings in a laboratory task. A task was presented to subjects as one examining how people perform a basic chemistry demonstration. Experiment 1 examined the effects of two locations of the warning (before and after instructions) and two different signal word presentations (WARNING and Note). An additional condition with no warning or signal word served as a control. No effects were found on time or accuracy. However, compliance (use of mask and gloves) was affected by the inclusion of the warning as well as by its location. Greatest compliance occurred when the warning was placed prior to the instructions. Experiment 2 replicated the effect of location. The addition of a printed statement placed before the instructions (with warning at the end) to read through the instructions before beginning produced intermediate compliance that was not significantly different from the warning beginning and end conditions.Observation revealed that when the warning message was at the end of the instructions subjects complied only when they saw the warning message before starting the task. These results indicate that i f warnings are placed in front of instructions the consumer is more likely to read and comply.