Home Experience Services Contact Us Seminars Attorney's Guide to Perception Resources
Drugs, Adverse Effects & Warnings

Marc Green

Warnings inform the consumer of potential hazards that are not open and obvious. If an object has sharp edges or burns with a flame, then the hazard is clear and requires no warning. If the hazard is not obvious, then warnings reveal the risk and are theoretically an important safety measure. Drugs are classic instances of products that can contain hidden "adverse effects." A pill's visual appearance says little about its effects or the hazards that it may contain. Drug label information, both warnings and usage instructions, is then presumably critical for safe product use.

The switch of many prescription drugs to over-the-counter (OTC) status has increased the importance of label warnings. Many medications that once required a prescription because of high potency or because of high possible abuse are now readily available. At the same time, the switch means that consumers lose the advice of the "learned intermediary," a physician and pharmacist, who might have counseled them on the drug's use and adverse effects. Lastly, today's consumers have a lower threshold of discomfort and are far more likely to use pills to relieve symptoms than were their parents.

Research, however, shows that consumers frequently ignore warnings and other information printed on the bottle's label. Here are a few findings:

  • One large-scale survey found that only 16-24% of respondents said that they read OTC drug label information on warnings and side effects upon first usage. Consumers also frequently ignore instructions on use. Almost half of the survey respondents said that they had exceeded recommended dose - if the recommended dose is good, than a larger dose must be better;
  • A behavioral study found that consumers also pay little attention to warning signs. Only 9% of regular consumers read a posted in-store warning sign about antacid medications.
  • Two surveys have found that a sizeable majority of consumers ignore label warnings to avoid driving after use.
  • Consumers fail to read and to follow label instructions for several reasons whose roots lie in normal cognitive function. The processing of warnings requires a series of mental processes. At each stage, there are processes that reduced the likelihood that drug information will affect behavior.

    1. Notice the warning. The consumer must attend the warning. While physical format may play a small role, the major factor affecting attention is meaningfulness (see "Inattentional Blindness"). Obviously the print must be legible and size, to some extent, can draw attention. However, meaningfulness is usually the key factor. Most environments overload humans with information, so people develop strategies for best allocating their limited attention. The common strategy is to learn what is relevant given the goal and to ignore the rest. In addition, repeated behavior becomes "automatic" or "scripted," a stereotyped sequence that once initiated runs off to completion with little or no conscious supervision. Most consumers have performed the routine of taking a pill hundreds or thousands of times: fetching, and opening the bottle, removing 2 pills, closing the bottle, ingesting the pills, drinking water, etc. Scripted behavior develops, in part, because most consumers have suffered no significant adverse effects. There is little risk, so the label information is irrelevant for achieving the goal. If the consumer has suffered an adverse effect, s/he may simply form categories that differentiate strong and hazardous medications from weaker ones (e.g., prescription vs. OTC.) One author, for example, noted that "consumers portrayed their non-prescription use as a routine, taken for granted activity, relatively divorced from active consideration of risk." Consumers then tune out the warnings, and to a lesser degree usage instructions, as unimportant and simply fail to notice them. (Another functionally equivalent possibility is that the warning is noticed, but quickly deemed irrelevant and then quickly pushed out of short-term memory. In either case, the consumer will not remember having seen the warning.)

    2. Read the warning. After noticing the warning/text symbols, the consumer must decide whether to read them. Drug labels usually contain lengthy text in very small print that takes considerable effort to read. The cost-benefit tradeoff requires a significant benefit to make the effort of reading worthwhile. However, reading warnings provides little value. Most people have had benign history with drugs, especially OTC medications. Consumers automatically assume that prescription drugs, as a class, must carry some risk. Why else would they require a doctor's approval? A hazard is therefore suspected, even though it is not obvious. Conversely, consumers generally believe that OTC drugs must carry little risk. Why else would they be freely available? Further, consumers likely associate a medication's potency with the seriousness of the disease that it treats; serious medical conditions require powerful medicine while mild medical conditions (coughs, colds, headaches, etc.) require only weaker, and therefore safer, medicine. Consumers also group products into equivalence classes that they treat as similar. Benign effects of one drug class can transfer to new ones. For example, a benign history with OTC drugs in general can reduce the perceived risk of new ones.

    3. Comprehend the warning. The person must understand the warnings. This means that the terms and language should be clear to consumers who may not be familiar with much medical vocabulary. Several studies have found that drug label information may be confusing. Further, warnings are often vague. For example, the warning "If symptoms persists, see a doctor" says little. How long must the symptoms persist? How serious should they be?

    4. Remember the warning. The consumer must be able to recall the warnings for two reasons. First, the consumer may not ingest the drug until some time after reading the label. For example, s/he might read the label at time of purchase but ingest the medication later at home. Second, consumers are most likely to read the label prior to first use. For subsequent doses, there is lower probability that the warning will be reread, so the warning must be remembered from the first use. The increased number of warning and instructions on drug labels creates information overload. Several studies have shown that memory for medical information falls as the amount of information increases. This makes excess warning highly counterproductive.

    5. Act on the warning. Warning effectiveness can be defined by its ability to merely inform of a hazard or by its ability to change behavior. These are two vastly different criteria because the leap from understanding to action may not occur. First, consumers frequently fail to heed a warning because it has low credibility. Most consumer drug experience is benign - they have previously used the drug (and similar drugs) with no ill effect. In fact, most people are constantly bombarded with warnings (many presumably driven more by fear of litigation than by safety concerns) about all sorts of hazards that never occur, so there is a general skepticism about warnings. Second, cost of compliance greatly affects warning impact. If a medication works especially well, is cheaper or is the only one available, then the consumer may decide to ignore warnings and instructions, especially since they have little credibility.


    Consumers frequently pay little attention to drug warning and instructions, either on label or information sheets. They tune out the information for many reasons, including development of scripted behavior due to repeated exposure without adverse effect, the massive number of "cry-wolf" warnings encountered in everyday life and, especially in the case of OTC medications, perception of low risk. Further, there is a relatively high cost to reading and/or complying with the information.

    These same factors affect the consumer attitude and behavior toward most common product warnings. Authorities may wish that people acted in some theoretically optimal way - carefully scrutinizing products, poring over warning and instruction information and always following proscribed procedures. It is merely wishful thinking to expect people to act this way because human nature is to adapt and to economize mental effort. Any attempt to develop effective warnings must start by accepting human nature as it is and not as one might wish it were.

    Other Topics
    Personal Injury: Road Accidents
  • Is The Moth-Effect Real?
  • Human Error in Road Accidents
  • Reaction Time
  • Let's Get Real About Perception-Reaction Time
  • Why PRT Is Not Like Gravity
  • Vision in Older Drivers
  • Weather and Accidents: Rain & Fog
  • Accidents At Rail-Highway Crossings
  • Seeing Pedestrians At Night
  • Underride Accidents
  • Rear End Collision: Looming
  • Night Vision
  • Distracted Pedestrians
  • Failure To See
  • Perception-Reaction Time (PRT) Programs
  • Twilight (3.3 lux) As A visibility Criterion
  • Human Error And Fault Tolerance
  • Why Pedestrians Die
  • Bicyclists! Read This To Save Your Life
  • Personal Injury: Warnings & Product Defects
  • Warnings and Warning Labels
  • Warning Effectiveness Checklist
  • The Psychology of Warnings
  • Drugs, Adverse Effects & Warnings
  • Are Warnings Effective?
  • Human Error Vs. Design Error
  • Product Misuse And "Affordances"
  • Safety Hierarchy: Design Vs. Warning
  • Thinking Like A Human Factors Expert
  • Personal Injury: Other
  • Diving Accidents in Pools
  • Falls Down Steps
  • Medical Error
  • Computer & Medical Error
  • Nursing Error
  • Criminal & Police
  • Errors in Eyewitness Identifications
  • Perceptual Error in Police Shootings
  • Eyewitness Memory Is Unreliable
  • Human Factors In Forensic Evidence
  • Intellectual Property
  • "Any Fool Can See The Trademarks Are Different"
  • Measuring Confusion For Intellectual Property
  • Color in Trademark and Tradedress Disputes
  • Color Functionality: A Case Example
  • Visual Human Factors
  • 33 Reasons For Not Seeing
  • Seeing Color
  • Determining Visibility
  • "Inattentional Blindness" & Conspicuity
  • Computer animation has perceptual limitations
  • Photographs vs. Reality
  • The Six Laws Of Attention
  • What is "inattention?"

  • | Home | Experience | Services | Contact Us  | Seminars/CLE | Attorney's Guide  | Resources |

    Copyright © 2013 Marc Green, Phd
    Home Page:
    Contact Us