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Article Excerpt
INTRODUCTION
Successful comprehension of warnings frequently requires an understanding of not only explicitly stated information but also information that may be implied. If a warning designer were to explicitly state every concept that needed to be communicated, the text would be overly repetitious, difficult to comprehend, and probably too long for the physical space for which it was designed. Many warnings attempt to convey a large amount of safety and instructional information in a small, physically constrained space (e.g., on a product label), requiring the reader to draw inferences about the warning's meaning. Product warning designers may leave out certain details, assuming people will use general and domain-specific knowledge to aid comprehension and make the correct inferences. Given the variety of hazards associated with even common household products, it is critical that this kind of naturalistic text successfully communicates the right information to product users.
An impaired ability to make inferences during reading could compound age-related text comprehension problems (e.g., related to memory and perception) that may already be experienced by older adults. Older adults need to be able to understand a variety of reading materials designed to help them function independently in the community. For example, understanding how to safely operate medical equipment and health care devices at home can reduce the amount of time spent in a hospital or doctor's office. Warnings and instructions found on common products such as medications, cleaners, paints, and polishes can be dense and complex, but they still need to be interpreted correctly to reduce the likelihood of an accident (for adults of all ages). Prior research investigating age-related effects on inferencing ability (the ability to derive logical conclusions from factual knowledge or evidence) and text comprehension has yielded mixed results (e.g., Graesser & Bertus, 1998; Light, Zelinski, & Moore, 1982). There has also been no research to date investigating the effects of age on comprehension for explicit or implied information used in actual product warnings. Previous work does, however, suggest that older consumers are generally exposed to the same types of products and warnings as are younger consumers (Hancock, Rogers, & Fisk, 2001).
The current research examined age effects on comprehension for explicitly stated and implied information used in real and fabricated warning texts. One primary goal was to determine how well younger and older adults correctly infer information from warnings and if age-related differences exist in inferencing ability. Age-related deficiencies could be observed for several different reasons. Deficiencies could be caused by memory retrieval problems experienced after a warning has been read, by differences in reader goals that affect how the warning is processed, or by differences in the degree to which real-world knowledge can be used to aid understanding. Another goal of this research was to determine how current product warning designs are understood by investigating how well people in different age groups comprehend warnings used on real consumer products. Even when warning information is clearly spelled out on a product, it is not clear if comprehension patterns differ across age groups, given that age-related effects on comprehension for real-world product warnings have not been previously investigated.
The relative contributions of memory and knowledge to age-related effects on warning comprehension were assessed by systematically varying (a) the influence of memory load and (b) the degree to which knowledge could be used. In both experiments, the role of memory was investigated by varying when the warning comprehension test was given (immediately after reading a warning or after a delay). The degree to which memory for information was emphasized in the test instructions was also varied. Participants were instructed to verify test items using specific details from the warning or by judging how consistent the test item was with the warning. The role of knowledge in warning comprehension was evaluated in Experiment 2 by varying the degree to which participants could use product knowledge to aid their comprehension (i.e., test items were displayed after the participant read either real warnings or fabricated warnings that were inconsistent with real-world product information).
Signal detection theory, when applied to the analysis of warning information, can be a useful tool for identifying the specific elements of a warning that are poorly understood. Signal detection analyses are also useful for discriminating between elements that may have differing levels of comprehension. In the current research, signal detection analyses were used to help interpret age effects on text comprehension patterns observed when participants processed explicit and implicit warning information. In addition to examining hits and false alarms, we computed perceptual sensitivity and response bias measures to determine if discrimination or response bias patterns could explain observed age effects.
GENERAL METHOD
Participants
Participants in two age groups (younger, older) participated in these studies. Younger adults were students at Georgia Tech who received extra course credit or financial compensation ($10/hr) for participation. Older adults were recruited from the Atlanta area and were financially compensated ($10/hr). All participants had at least 20/40 near vision.
Materials
The warning texts, verification test (i.e., comprehension test), and filler task were programmed and individually administered using E-Prime Version 1.0 (Psychology Software Tools, Pittsburgh, PA) via IBM-PC computers. All other tests were group administered in paper-and-pencil format.
Ability tests. Tests of perceptual speed (Digit Symbol Substitution Test, Wechsler, 1981), memory span (Reverse Digit Span Test, Wechsler, 1997), and verbal ability (Shipley Vocabulary Test, Shipley, 1940; Nelson-Denny Reading Test [Form H], Brown, Fishco, & Hanna, 1993) were administered.
Warning texts. We developed 48 two-sentence texts from warning labels found on common, real-world products (hereafter referred to as knowledge-consistent warnings). Of these, 6 texts came from cleaners/detergents, 17 from over-the-counter medications, and 14 from paints/polishes. Products in these categories are typically accompanied by detailed warning information, and previous research has suggested that younger and older adults frequently use these specific types of products (Hancock, Rogers, et al., 2001). In addition, 11 texts were taken from miscellaneous household products (e.g., bug repellant, batteries). Warning texts were taken verbatim from the product labels, with a few exceptions. Very long sentences were shortened, and some sentences were modified to ensure that specific information was explicitly stated or implied; references to brand names or generic names were also removed. Table 1 depicts an example (knowledge-consistent) warning and relevant test items.
Verification test. A verification test involved determining the truth/falsity of four statement types: explicit-true (ET), implicit-true (IT), explicit-false (EF), and implicit-false (IF). ET statements restated information explicitly stated in the warning text (verbatim or paraphrased). IT statements represented inferences that could be drawn from the text. EF and IF statements were statements that directly contradicted specific ET and IT statements, respectively. For every warning text, two statements of each type were developed. All test items were validated in a normative study with 43 older and 42 younger adults (see Hancock, Fisk, & Rogers, 2001).
Filler task. On delayed verification trials, participants performed arithmetic problems for 25 s (Experiment 1) or word-finding items for 2 min (Experiment 2) after reading a warning, before verifying a test statement.
Product/warning familiarity. A questionnaire about product usage patterns and warning habits/beliefs was administered to assess familiarity with the kinds of products on which the warning texts were based. Questionnaire data were also used to assess the relationship between attitudes about warnings and comprehension/ memory for warnings. This questionnaire was based on one used in previous work (see Hancock, Rogers, et al., 2001). The current results pertaining to product/warning familiarity are consistent with that previous work and will not be discussed further here.
Design and Procedure
Test type (immediate, delayed) was manipulated within participants; instruction type (explicit, consistent) was manipulated between participants. Age was a grouping variable (younger, older). Dependent variables were hit/false alarm rates, perceptual sensitivity, and response bias for the four statement types on the verification test.
After providing informed consent, participants completed the ability tests and the vision test, and then they took a 10-rain break. Participants then completed a choice reaction time task, using the primary keys to be used in the experiment, to familiarize themselves with reading from the computer monitor and using the keyboard. (For both experiments, there were no age-related differences in accuracy on this task, although older adults were generally slower than younger adults to make responses.) For the verification test, participants were told they would be reading texts that contained information similar to consumer product information (no other information about the texts was given). They were instructed to read at their normal reading rates. Each warning text was displayed on the computer screen one sentence at a time. All sentences appeared left-justified at the top of the screen. For each screen associated with the presentation of a text sentence, the phrase "PRESS SPACE BAR TO CONTINUE" was displayed at the bottom of the screen. Pressing the space bar resulted in the removal of the current sentence and either...
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