Searching for Fluorescent Colored Highway Signs: Bottom-Up versus Top-Down Mechanisms

A novel inattention search paradigm (Mack & Rock, 1998) was used to assess the visual efficiency of fluorescent colored relative to nonfluorescent colored highway signs in a laboratory setting. Unexpected presentation of a fluorescent colored search target was not accompanied by an improvement in visual search time. However, visual search times improved dramatically once the participants developed the expectancy that the target feature would be presented on a fluorescent colored singleton. This pattern of results suggests that many of the visibility advantages attributed to the use of fluorescent colors in safety applications may be mediated by top-down attentional mechanisms rather than bottom-up (preattentive) mechanisms as previously assumed.