Posts Tagged ‘security scanning at airports’

Screening Performance

July 16, 2019

This post is based on a book by Stefan Van Der Stigchel titled “How Attention Works: Finding Your Way in a World Full of Distraction.” Radiologists have a difficult task when screening for breast cancer. Studies in the Netherlands have shown that the initial screening procedure has a detection probability of about 70%. So radiologists fail to detect incidences of cancer in over one quarter of all women who do in fact have breast cancer. These radiologists are not incompetent; they have a very difficult cancer to detect.

There is also the problem of falsely detecting a cancerous tumor. Additional examinations are very painful, and reacting to every minimal sign would lead to a lot of unnecessary discomfort. The chances of detecting a tumor on the basis of a minimal sign are known to be very low. But when scans in which a tumor was missed are checked again, the tumor usually turns out to be visible. The radiologist now knows that the scan does in fact contain a tumor and there is a maximum probability of actually finding it.

Scans are also done at airports for checking hand luggage. Security scanner operators spend hours every day searching the contents of bags and suitcases. Of course, the education and training of these airport security scanners is much less than that of radiologists. And the chance of finding dangerous content in these bags is much lower than the chance of correctly detecting dangerous objects in luggage. So fake explosives are placed in luggage for purposes of training and assessment. There are reports that operators fail to spot up to 75% of the fake explosives that are hidden in bags for test purposes.

An Americans study in to the performance of airport security personnel revealed that having to scrutinize scans on a daily basis helps them to be more precise when carrying out other unrelated search work. Out of a group of test subjects who were asked to find a well-hidden object on a computer screen, 82% were successful. A group of professional security scanner operators scored 88% for the same test although they did take longer to complete the task compared to nonprofessionals.

If you would like to check your prowess as a security scanner operator you can down load Airport Scanner, a free app ( that allows people to play
the task of finding dangerous items in luggage scans. This app has been a huge success worldwide and has millions of users. This app is partly funded by the American government, which is pleased with the amazing amount of information they are able to glean from the game. Researchers are also involved in the development of the game, and the first scientific articles were recently published containing the data retrieved from one billion searches. Some players have become so addicted that they have already competed thousands of searches. And this has provided developers with the opportunity to insert certain objects, only at sporadic intervals (in less than 0.15% of the searches). Dr. Van Der Stigchel notes that this research could not be done in a laboratory because the research subjects would end up running screaming from the lab after being subjected to hours and hours of tests. Based on a probability of 0.1%, an object will appear once every 1,000 searches, and in order to reach any firm conclusions about a player’s performance when attempting to find an extremely are object, 20,000 searches would need to be conducted. These data are now available thanks to the Airport Scanner app, and it has proven beyond doubt that players/professionals frequently fail to spot these rare, hidden objects.