‘Same person’ pairings show evasion disguise. ‘Different person’ pairings show impersonation disguise. Credit: University of York.

Superficial disguise, such as changing hair color or facial expression, really works. In a new study, strangers were asked to judge whether two photos showed the same or a different person. Simple disguises reduced participants’ face matching ability by 30% even when they were warned that some people showed in the photos had changed their looks.

Catch me if you can!

The Psychologists at the University of York, led by Dr. Rob Jenkins, wanted to investigate the effectiveness of deliberate disguise. Individuals seeking to evade criminal prosecution or security checks will use all sorts of gimmicks to disguise their usual appearance — and the researchers found that it can be quite effective.

The models recruited by the researchers were given ample time to alter their appearance. They could use make-up, change hair color and style, and grow or shave facial hair. They were not allowed to use hats, glasses, and other accessories since these are prohibited in real-life security settings, such as during a passport check or security checkpoint. In order to motivate participants to take their disguise seriously, researchers offered a generous financial incentive.

Besides evasion disguise — altering the appearance to not resemble one’s usual self — researchers also examined the effectiveness of impersonation disguise — trying to look like another person. The researchers found that evasion disguise is much more effective than impersonation disguise. Impersonation disguise is often used by people traveling with a stolen passport or during cases of identity theft, while evasion disguise is most often used by criminals seeking to evade the law, but also undercover policemen or those in witness protection programs.

The results suggest that evasion disguise can easily fool strangers who aren’t used to a person’s facial cues, but is much less effective against people who are familiar with the person seeking to evade.

“We shouldn’t be complacent about deliberate disguise in criminal and security settings. When someone puts their mind to concealing their identity, it can be very effective,” Jenkins said.

“Familiarity with the people who are disguising themselves improves accuracy. When you are unfamiliar with a face you are easily fooled by superficial changes in hairstyle or colouration.”

“However, when you ‘know’ a face you tend to rely more on internal facial features – the eyes, nose and mouth – which are much harder to alter.”

In the future, the researchers would like to test how automatic face recognition fairs against humans at the same tasks.

The findings were published in the Journal of Experimental Psychology: Applied.