Pictorial symbols may be a valuable form of communication for conveying safety information. Symbols can enhance text comprehension, facilitate top-down processing of a safety message, be better perceived than text in degraded conditions, and be more rapidly perceived than text (for a review, see Rogers, Lamson, & Rousseau, 2000). Symbols may also be useful in conveying safety information to a diverse audience of consumers and product users. For example, people with low of impaired vision might perceive and comprehend symbols more readily than information presented via text. Although people with low literacy levels may have difficulty understanding different types of safety and warning messages if detailed text is used, they may have higher comprehension for symbolic information. Furthermore, non-native-English speakers need not rely on their knowledge of the English language to correctly interpret symbols.
For older individuals, comprehension of safety information presented in symbolic form may also be better than when the same information is presented in textual form. The typical older adult may experience visual, memory, and text comprehension impairments (e.g., Craik & Salthouse, 1992), all of which could contribute to difficulties comprehending text messages. Furthermore, besides possibly being exposed to safety symbols at work, there is evidence that older adults continue to use a variety of household products that may display, symbols conveying usage and safely information (Hancock, Fisk, & Rogers, 2001). Thus it is important that these individuals be able to interpret symbols in the way, designers intended them to be interpreted.
Unfortunately, the existing empirical evidence is mixed with regard to older adults' comprehension of symbols, For example, researchers assessing comprehension for highway icon signs typically have found no significant age-related differences for symbol comprehension by' younger and older drivers (e.g.. Halpern, 1984; Kline & Fuchs, 1993: Kline, Ghali, Kline, & Brown, 1990). However, other research involving symbols used in railway stations (Zwaga & Boersma, 1985), on medication bottles (Morrell, Park, & Peon, 1990), and on consumer products (Easterby & Hakiel, 1981: Hancock, Rogers, & Fisk, 2001) has found evidence for an age-related deficit in comprehension. To further complicate the issue, at least one study has reported that older adults have greater comprehension for certain symbols than do younger adults (Mayer & Laux, 1989). It is important to understand how people of different ages process this type of warning information, and a lot Call be learned from studies of symbol comprehension about how age affects specific cognitive processes in a real-world problem space. Findings from this kind of empirical research can be applied toward improving warning presentation and design as well as toward furthering a theoretical understanding of principles underlying cognitive aging.
Differences in the testing methods used by researchers may have contributed to the mixed results observed across studies. For example, open-ended, multiple-choice, or ranking tests may be used to assess comprehensibility of symbols. Specific methodologies for designing and evaluating safety symbols have been asserted by the American National Standards Institute (ANSI: National Electrical Manufacturers Association, 1991, 1998) as a means of standardizing the way symbols are developed. The standards recommended iterative testing, using multiple candidates for the same concept, using multiple tests, and testing appropriate user populations. ANSI dictated that a given symbol should be associated with an 85% correct response rate for it to be considered effective (i.e., reducing reliance on text messages and symbol training). A number of studies, however, have found common ANSI symbols to be associated with accuracy rates below 83% (e. …