Age-related differences in warning symbol comprehension and training effectiveness: Effects of familiarity, complexity, and comprehensibility

or arbitrary symbols). Some suggestive evidence comes from Lesch (2004) who found that age-related differences in warning symbol comprehension appeared to be related to the rated comprehensibility of the symbols (i.e. given the symbol’s verbal label, how easy is it to understand this symbol in isolation?). The symbols that were initially well understood by the older adults, as well as those symbols that benefited from training, tended to be rated as highly comprehensible. Furthermore, while training eliminated effects of familiarity for both younger (18–35 years of age) and older adults (50–65 years of age), comprehensibility continued to correlate with performance by older adults such that symbols that received low ratings of comprehensibility were more poorly understood. It was suggested that comprehensibility reflects the extent to which the symbol is capable of triggering appropriate, context-specific information and that older adults’ performance hinges to a greater extent on effective cues to knowledge. However, as the study was not specifically designed to assess comprehensibility effects, a limited range of comprehensibility values was included. In the discussion thus far, we have documented age-related cognitive changes that have implications for warning symbol comprehension. The manner in which symbol comprehension is gauged also merits special consideration, as age-related differences in symbol comprehension can also be due to the method of measurement. Some guidelines (e.g. ANSI Z535.3 2007) suggest that warning symbol comprehension should be assessed using an open-ended test in which the respondent is asked to describe the symbol’s meaning in their own words. However, since word-finding ability and verbal fluency tend to decrease with age, test measures that emphasise verbal output may underestimate comprehension for older adults. Multiple choice tests, on the other hand, minimise verbal output by requiring the respondent to select the correct answer from a pool of distractors. However, 880 M.F. Lesch et al. Downloaded by [M.F. Lesch] at 06:05 07 November 2011 due to age-related declines in selective attention and inhibitory efficiency, older adults may have greater difficulty rejecting incorrect responses. That is, based on their relationship with the target, plausible distractors will be somewhat active in memory. If inhibitory processes are working properly, those incorrect (but related) responses will, effectively, be ‘shut off’, and the correct response ‘wins’. If inhibitory processes are not working properly, there will be a strong competition among possible responses resulting in a decreased likelihood that the correct response is selected. In light of age-related changes in verbal abilities and inhibitory processing, we suggest the use of a semantic relatedness task to assess comprehension in older adults (see Lesch 2005). In this task, a symbol is presented with a verbal label and the participant must decide whether the verbal label corresponds to the meaning of the symbol. The semantic relatedness task, like the multiple choice test, has the advantage that verbal output is not required. However, unlike a multiple choice test, the correct and distractor labels are presented on separate trials so as to minimise any effect of inhibitory (in)efficiency.