Harness the power of the crowd to improve airport security and cancer detection, study suggests

The detection rate of weapons moving through airports and tumours growing in the human body can be significantly improved by having two people independently checking scans, a new study has found.

Researchers from Brunel University London found that having two people independently screening baggage scans was over 25% more effective at discovering banned contraband than current practice – having one person check two separate scans of the same bag.

Its hoped the study, 'It's not a tumour': A framework for capitalising on individual diversity to boost target detection , published in the journal Psychological Science, could make 'trained observers' – for instance, those working in airport security, radiology and military reconnaissance – better at detecting the rare items they're looking for.

"There is a known problem with detecting rare targets," said Dr. Jennifer E Corbett, an honorary lecturer for Brunel's College of Health and Life Sciences.

"When you go to the airport, they always seem to find the bottle of water in your bag – it's a very common item, so people have a mental template. They'll just find it. But with rare targets like weapons and guns, people see these far less frequently, so are more likely to miss them."

Dr. Corbett, who co-authored the paper alongside Brunel's Dr. Jaap Munneke, says the problem lies with the human visual system, which is only capable of processing a few objects in detail at any given moment.

The brain averages out redundant and specific information, filling in the spaces based on prior knowledge. As a result, infrequent objects – those that the observers aren't expecting to see – are often missed.

However, two people independently looking at the same scan perceive it differently, significantly increasing the possibility of infrequent items being spotted.

"We found that when we pair the estimates of two people who don't know they're working together – they have no interaction whatsoever – there is a huge improvement in detection, just by capitalising on the diversity of people's judgements," said Dr. Corbett.

To test their ideas, the researchers conducted two experiments – one which challenged participants to undertake airport screening, and the other mammogram screening.

In the airport screening experiment, 16 participants – non-professionals – were shown an image with nine objects for half a second, and then asked to indicate whether they'd like to call the image back, based on whether they detected a target object.

"The experiment tested weapons detection as well as simple detection tasks," said Dr. Corbett.

"We found that not only did pairing observers estimates improve detection in both types of tasks, but that pairing individuals estimates from the simple task in a way that maximized the decorrelated patterns actually improved the performance in the separate weapons task."

The researchers discovered that when they paired the detections of two people who worked individually and independently, they not only saw an increase in the detection of rare objects, but also a reduction in the likelihood of harmless items being wrongly flagged as suspicious.

For the second experiment, 18 participants were taught how to identify a tumour on a mammogram, before being shown 400 unique scans where 5% had a tumour present, and then another 400 where 50% had a tumour present.

In both cases, a significant increase in detection rate was observed when two individuals' results were averaged.

More information:
Jennifer E. Corbett et al. “It’s Not a Tumor”: A Framework for Capitalizing on Individual Diversity to Boost Target Detection, Psychological Science (2018). DOI: 10.1177/0956797618784887

Provided by Brunel University