Some police dogs can sense the fear that can alter the smell of a person. And that could be a bad news for finding missing people whose genetic predispositions make them more prone to stress.

Genetic Worker Francesco Sessa Announces 22. February at the annual meeting of the American Academy of Forensic Sciences that trained police dogs could not recognize stressed people with a certain version of the gene that is involved in stress management. Dogs had no problem identifying volunteers in men and women who were not stressed. The study can help explain why dogs can work flawlessly in training, but have difficulty watching people in real situations.

Everything affects the SLC6A4 gene

Sessa and colleagues from the University of Foggia, Italy wondered if fear could change a person's normal smell and prevent dogs from finding the missing people. The researchers also investigated whether human genes could facilitate or complicate dogs in finding certain clues. Previous studies have already combined different versions of the serotonin transport gene SLC6A4 with stress management. People with a long version of the gene tend to manage stress better than people with a short version, says Sessa.

He and colleagues hired four volunteers - men and women who have a long version of the gene and men and women with a short version. Each participant wore a scarf a few hours a day to print his scent on the garment. Then the scientists brought the volunteers to the lab. In the first session, volunteers wore T-shirts and were not exposed to any stress. The team also divided women's and men's shirts in particular.

The result of the experiment

After sniffing the scarves, two trained police dogs had no trouble identifying any of the volunteers in the 10 T-shirt lineup. Dogs identified each of the volunteers in three of three trials. Furthermore, scientists stressed the volunteers by letting them publicly speak. The heart of the participants ran and their breathing became shallow, which meant they were scared, Sessa said. This stress can cause a change in their body odor and dog confusion.

In two of the three experiments, the animals chose stressed T-shirts belonging to a man and a woman with a long version of the gene. But no dog could identify stressed people with a short version of the gene, suggesting that the natural smell of these people is changing more under stress. Scientists must confirm their findings in a larger study, Sessa said. And the team has not yet begun to analyze how fear or stress changes body odor.

Criminologist and Forensic Scientist Cliff Akiyama, founder of Akiyama and Associates says:

"It could probably explain why dogs can find someone more easily and not someone. Our body responds to trauma very differently. ”

Everyone reacts differently to stress

Fear can cause a flood of stress hormones that cause some people to stiffen, others to fight, and others to run away. It seems that the same hormonal flood can change a person's smell, says Akiyama. But that does not mean that dogs are unnecessary in finding missing persons. Many people are abducted by parents, relatives or other people who know the victims, he says. Therefore, the weariness is not always afraid of their kidnappers, and perhaps they leave their odors unchanged.