CHAMPAIGN, Ill. - Baggage screeners have just seconds amid loud airport noises and the pressure of rushed airline travelers to scan X-rays of carry-on items for weapons. How good they are at finding one may depend on the specificity of their training, say researchers at the University of Illinois at Urbana-Champaign.
The findings, published in the May issue of the journal Psychological Science, suggest that initial training of federal airport screeners needs to last long enough for them to be exposed to a variety of weapons, and continuing education may be necessary to expose screeners to potentially new and unexpected ones.
The research was conducted at the Beckman Institute for Advanced Science and Technology at Illinois, using two-color X-ray images of carry-on baggage containing knives provided by the Federal Aviation Administration, which funded the study. Eye-tracking techniques captured where and how quickly the participants scanned through clothing, hair dryers, pill bottles and other items in each X-rayed piece of luggage to find a weapon.
The laboratory training of 16 volunteer young adults helped them to become more efficient in spotting knives in the baggage, but their improvements did not carry through when the sizes of the knives were changed in newly examined images, said principal investigator Arthur F. Kramer, a professor of psychology.
"We found that the effects of training were beneficial," Kramer said. "Clearly people improved on their abilities to spot specific weapons in a search. However, we found that training, for the most part, was relatively specific to the items on which screeners were trained. There wasn't a lot of transfer. If the expectation is that we can train screeners on one set of weapons and expect them to transfer that ability to another kind of weapon, that is not the case."
The X-rayed baggage - 89 pieces in all - was presented on a 19-inch monitor. Two sets of four differently sized knives were used and inserted at random locations and orientations. Each participant took part in five sessions of 300 trials each.
"We found that training did not have much of an impact at all on how quickly they got their eyes to the area of a weapon," Kramer said. "What improved was how quickly they detected a weapon once they looked into the right region. They became better able to differentiate the weapon from other materials, but not better able to get their eyes into the right location more quickly."
When different, unfamiliar targets were introduced, the number of eye movements of the participants increased before the targets were found, and the probability of finding them decreased.
The goal is to reduce both the numbers of false identifications and the actual misses. That will require an approach that develops the capacity to perceptually organize and recognize a variety targets in security imagery, Kramer said. "You have to train relatively broadly if you want to get better across the board. I think that's increasingly important given the creativity of terrorists."
In addition to Kramer, four other Illinois researchers were involved in the study: Beckman Fellow Jason S. McCarley (now a professor at Mississippi State University and who will join the Illinois faculty this summer); doctoral student Walter R. Boot; Christopher D. Wickens, professor of psychology and head of the Institute of Aviation's Human Factors Division at Willard Airport; and Eric D. Vidoni, an undergraduate student.