Licensed Professional Engineers



A newsletter dedicated to keeping attorneys informed of the technical side of product liability cases.

Issue 60: Vol. 1 April/May 2014

© 2014 M.A.S.E. LLC

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FORENSIC CLUES # 60 - "The Psychology of Warnings" by John L. Ryan

Engineering design principles call for a hazard analysis of any product to identify hazards. Once these hazards are identified, they can be mitigated to protect the end user. The most effective method is to eliminate the hazard from the design. If eliminating the hazard is impossible, the hazard must be safeguarded to neutralize the hazard. Only if safeguarding is impossible should warnings be used as a primary source of safeguarding. This Clues discusses the psychology of warnings, and information processing theory as it relates to warning design. Information processing theory is a psychological model for how humans process information. The principles of this theory can be applied to improve the effectiveness of warnings.

Perception is the first stage of information processing. Perception includes sight, sound, touch, smell, and taste. Warning comprehension and effectiveness normally involve sight, but other senses may come into play, especially sound if audible warnings are used. Perception of information must first occur before any further, deeper, processing of the information is possible. Perception does affect warning design directly also. Product users must be able to see and perceive the elements of the warning label. To ensure this, designers must be aware of the physical characteristics of the warning label such as the size of the warning label, text size, warning location, etc.

Attention is the next stage of the information processing model. Once a person perceives a warning label, to further process the warning label information, the warning label must be attended to. Just because something is perceived doesn’t necessarily mean that a person’s consciousness and thoughts will be focused on the warning label. In many work environments, there are a lot of different loud noises, cluttered work areas, and random activity that can prevent a person from focusing their attention on any one stimulus. This factor must be carefully planned for – the warning label must capture the attention of the product user in order for the warning label to be processed on the next level. Some of the same factors that affect perception also affect attenuation. The size of the warning label must be sufficient to attract one’s attention and the location conspicuous enough, while other factors such as signal words and color combinations have an impact on the likelihood of a warning catching a person’s eye. Attention is affected by habituation, a decrease in responsiveness to a specific stimulus as a result of repeated experience with it.

Comprehension is the next stage of the information-processing model. Once a warning is perceived and attended to, it must be understood in order for it to effectively prevent exposure to the warned hazard. Taking comprehension into account can be difficult for warning label designers because such variables as mental abilities and experiences vary widely from person to person. Engineers work with statistics and norms. Physical characteristics of certain products will often be created using anthropomorphic values for the “average” person. Warning comprehension has to occur by all product users, not just the average user. Comprehension can be increased using explicit warnings, which are warnings that give specifics about hazards, giving definite instruction on what to do and what not to do, as well as the consequences for failing to comply. Illiteracy is an issue with comprehension, as is non-English reading skills. Pictograph warnings are a potential solution for both illiterate and non-English speaking people. Studies have shown the universality of pictograph warnings.

Beliefs and attitudes are the next stage of information processing. We learn from our experiences and modify future behavior based on past experiences. This same idea affects warning compliance. Everyone has preconceived ideas. The preconceptions of familiarity and perceived hazard affect warning effectiveness.

Familiarity with a product has a high degree of impact on warning compliance. Numerous studies have shown that the more familiar a person is with a product, the less likely that person is to read warnings on a product, even if that product is a different model, style, or made by a different manufacturer. The inverse is also true. Studies have shown that when someone has a low level of familiarity with a type of product, there is a greater likelihood that the warnings will be actively sought out, read, and complied with. This familiarity effect is the result of beliefs formed from prior experiences.

After a person integrates his or her attitudes and beliefs in the response to the warning, in order for the warning to be effective, the person must comply with the warning. This is the final goal of warnings – compliance. In the information processing model, a person’s motivation is the final step. In order to have any chance of compliance, the first stages of information processing, perception, attention, comprehension, beliefs and attitudes must be passed successfully. Any break in the processing of the warning label will result in compliance failure.

Motivation for an activity is largely dependent upon the cost of performing the activity. A cost for performing an activity could be an expenditure of time, effort, money, or other perception of cost. If the cost of an activity outweighs the benefits from that activity, then the activity will not be performed – there will be no motivation. If a person perceives a warning’s cost to be greater than the perceived benefits, then the person is unlikely to comply with the warning. Often it will be an issue of cost of time or convenience. Following the instructions of a warning can make the task last longer. This effect can be countered using the same principle. If the perceived cost associated with noncompliance with the warnings is increased, this can balance or negate the costs affecting motivation. The easiest way to increase the cost associated with noncompliance is describing explicitly the potential negative outcomes if a warning is not heeded. Using terms like “serious injury or death” may be ineffective due to habituation – people have seen this phrase a million times in a million different places. A noncompliance consequence that is explicitly stated will have a greater chance of being effective. A statement such as “will cause amputation of hand” may be effective in increasing compliance.

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