Funny I should have mentioned conjunction search the other day, since this post is all about new research by Jeremy Wolfe who has and continues to contribute to the visual search literature.
In this new work, already mentioned on i09, Wolfe and his former research assistant Michael van Wert investigated complex visual search as it applies to baggage scanning at airport security. When the target being searched for (i.e., weapons) does not appear frequently, detection rates go way down. Even if it is detected, people have a hard time inhibiting the motor response of saying “no, I didn’t see anything.”¹
Of course, human difficulties in searching for rare events is nothing new. The big contribution of this work was to determine that we go through two decision criteria when searching and each affects our response time and our accuracy.
¹I’m liberally translating; these aren’t the specifics of the study method.
The primary sources mentioned in this post can be found:
Another good article with implications for the TSA:
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Interesting airport security research: when guards don't find weapons frequently, their ability to detect them reduces. http://bit.ly/cAKsgj