Perceived effectiveness of environmental warnings

This stultv' examined perceived effectiveness of warning signs for various hazard situations. Four-statement signs contained a signal word, a hazard statement, a consequencestatement, and an instruction statement. Four additional three-statement signs, each with a different stetement systemetically removed from the four-statement sign, were used, for a total of 5 signs for each hazard sItuation. The results of Experiments I and 2 indicated that removing content statements reduced perceived effectiveness. Hazard and instruction statements were the most important statements, showing the greatest decrease in effectiveness when deleted. Signs for the most hazaroous situations were perceived as the most effective warnings. Experiment 3 examined redundancy of statements in a sign. The results suggested that the deletion of redundant statements, particularly signal words, had less influence on effectiveness. The hazard statement showed the lowest redundancy consistant with it producing the greatest effectiveness decrement when deleted. INTRODUCT I ON As our society becomes more technologically advanced we must deal with increaSingly more complex systems. Used appropriately these systems are capable of dramatically improving the quality of our lives. However, misuse of these systems has the potentia) to produce bodlly injury or death. The first line of defense against Injury from hazardous situations is to "design out" the hazard and the second is to provide the necessary safety barriers. However, technology and/or costs may preclude designing out hazards, and adequate barriers are not always possible. Furthermore, proliferation in the variety and complexity of new technological systems decreases the likelihood that users will recognize the potential hazards. Even if users recognize that a hazard exists, they may misjudge the probablity of sustaining injury (Slovic, Fischhoff, and Lichtenstein, I 979) or the severity of the consequences. Hence the user must be directly informed of the exact nature and magnitude of the hazard, its potential consequences, and the appropriate and prohJbited behavior in the hazard area. Warnings, although considered a last line of defense in the effort to protect the user from potential hazards, have become Increasingly important. In recent years, personal injury and product liability litigation has presented issues ralevant to the Human Factors professional. One issus of increasing concern has been the effectiveness of warnings. It is important to note regarding effectiveness is that "the ultimate criterion is whether the warning has actually modified human behavior" (Peters, 1984). In essence behavioral effectiveness asks, has there been a reduction of undesirable and unsafe acts that would otherwise have occurred without the warning? A serious obstacle to conducting behavioral investigations is the absence of an appropriate methodology. One difficulty Is the construction of a re8lietic and believable scenario. Obtaining behavioral measures through observation is also difficult due to the relatIvely low frequency of critical 664 incidents. Controlled experimentation on effectiveness generates the problem of maintaining ecological validity without presenting the subject wIth a truly hazardous situation. Also there are problems of ethics in conducting .studies concerning hazardous situations.