Who's lying? Who knows?

Li Qian / SHINE

Is eyewitness memory reliable? Is it easy to identify a face that you see? How to detect a liar? Psychologists from New York University Shanghai gave a lecture, explaining these questions, to local detective story fans on Saturday in Shanghai Science and Technology Museum.

Professor Pekka Santtila pointed out that false identifications are the No.1 reason for wrongful convictions. “In the US, 250 innocent people were convicted because of false identifications and later released,” he said.

There are three stages of memory, starting with putting things in the memory, then keeping them there and finally recalling them. 

Why we can’t totally trust our eyes and memories?

First, it depends on the distance and time. It can be easily understood that if you are called to recall something that occurred one month ago, you could cannot remember the details.

His study also showed that incorrect identifications are 1.6 times more probable if the witness and the targets belong to different ethnic groups. And if the target carries some weapons, witness will focus more on weapons than the face.

Besides, witnesses may point out someone looking familiar with the criminal if they are granted a lineup of some photos of suspects. Actually, the criminal is not among the lineup but witnesses will still make the choice because police ask them to do so.

Shumpei Haginoya, who had worked for police department in Japan, said there are several signs of lies. Liars will use more negative words such as “I don’t know,” give short responses and less amount of information. Also, they will respond in higher tone of voice and in longer reaction time, as well as appear in less nodding and body movements.

“They have to try every effort to think how to lie to investigators and thus they can’t show other body movements,” he said. “It is interesting that tests showed liars will get more sweats but slower heart beats.”