Quantifying and predicting the effects of basic text display variables on the perceived urgency of warning labels: tradeoffs involving font size, border weight and colour

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Abstract
Design variables surrounding the presentation of signal words in warnings have been previously shown to affect performance, or variables likely to be related to performance. The present study emphasized the signal word WARNING by presenting it in red, surrounded by a red border. It was at the head of an otherwise black pesticide label that used 8-point type. A study using 24 undergraduates investigated the effect of signal-word font size (8 to 32 points), white space around the signal word (2 to 32 points), and border width (1 to 8 points) on the rated urgency of the label. A measure of the aesthetic merit of each label was also obtained from nine design students and professionals. Seven levels of each variable were used, covering the practically-useful range of each variable in the circumstances. Results showed a linear relationship between each variable and perceived urgency, with text size having the greatest effect, followed by border width. It was shown that, within the variable ranges used, the perceived urgency of the emphasized signal word resulted from the sum of the urgencies associated with the separate dimensions used in the emphasis. Tradeoffs are discussed—for example an increase of 4 points in text size produced the same increase in urgency rating as produced by an increase in border width of 2-3 points. A second study, using a further 24 students, compared the red labels with labels in black only. It was found that the signal word had to be approximately twice as big in black as in red to give the same perceived urgency. Design implications of the finding that the most urgent labels are not necessarily the most aesthetically pleasing are discussed.