Increasing the frequency of targets being presented in visual search (otherwise known as target prevalence) increases the chance that the targets will be detected. Similarly, decreasing the target prevalence reduces the chance that targets will be detected. This has been highlighted as a cause for concern in applied environments such as airport X-ray security screening where real targets (guns, knives, explosives) are very rare indeed.
The purpose of this project is to examine the potential causes of the impact of target prevalence, its relationship with expertise, and the role that prevalence plays in search for multiple targets. Results show that conducting search for two targets when one target appears at a higher prevalence level than the other will result in the higher-prevalence target being detected regularly, at the expense of the lower-prevalence target. The findings have implications for airport security screening, in which screeners search for bottles (frequently occurring) and explosives (infrequently occurring).