This paper has two objectives: to identify and review factors that research has shown to be most significant in determining the
effectiveness of warnings; and, to offer suggestions regarding challenges and opportunities for future research on warnings. In order for
warnings to be effective, they must accomplish two objectives: they must be noticed and encoded; and they must provide understandable
information needed for recipients to make informed decisions regarding compliance. A number of variables or factors have emerged as
being especially significant in determining whether or not a warning achieves these objectives. These factors include both warning system
design variables as well as characteristics of the target audience and the situation in which the warning is presented. While there has been
significant progress in understanding the factors that influence warning effectiveness, there are also remaining challenges and
opportunities. Challenges include issues associated with growing international trade such as language barriers, literacy and cultural
values. Innovative approaches and opportunities are offered by developing communication technologies.
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