What does airport baggage screening have to do with cervical cancer screening?

Abstract

At the most obvious level, baggage screening and cervical cancer screening are both visual search tasks in which an observer searches for targets in visual displays containing distracting items. This talk will introduce you to some of the basic principles that have been uncovered in many laboratories over the last thirty years and more. More than this, however, baggage screening and cervical cancer screening share several other properties. They are both socially important, difficult tasks where ‘miss’ errors may be a matter of life and death. Of most relevance to this talk, they are both tasks involving search for rare items – what we will call low ‘target prevalence’. We have examined the effect of target prevalence on the likelihood that targets will be missed in a variety of visual search tasks including simulations of baggage screening. Miss error rates are much higher at low prevalence (targets present on 1%–2% of trials) than at high prevalence (targets present on 50% of trials). In several experiments, we have shown that this prevalence effect is very robust. It can be replicated with different types of stimuli from oriented lines to x‐ray images of luggage. I will describe a couple of ways to reduce or eliminate this effect. Finally, I will demonstrate that, even if a search task is easy, you can readily miss something that is happening right in front of your eyes.