Sessa, a researcher from a University in Italy, investigated whether fear/stress could potentially make it harder for a dog to sniff out someone and also whether genes might make it harder for dogs to sniff out as well. We already know through previous studies that the serotonin transporter gene was linked to stress management. It was found that people with the short version of the gene did not handle stress as well as the people who had the long version of the gene.
Sessa got 4 volunteers for his experiment, a man and a woman with the long version of the gene and a man and a woman with the short version of the gene. In the first part of the experiment the four volunteers wore a scarf for a few days in order to imprint their scent onto it. The volunteers were then sent to a lab where they wore T-shirts for a while and were not placed under any stress. In a line up with 10 T-shirts, two trained police dogs did not have any trouble identifying the volunteers after sniffing the scarves. The dogs were right three out of three times, no matter who had the long gene or who had the short gene.
In the second part of the experiment, the volunteers were put under stress by public speaking, and the stress could have caused the volunteers body odors to change. The two trained dogs were able to sniff out the man and the woman's t-shirts with the long version of the gene two out of three times. But for the two people with the short version of the gene, the dogs were unable to sniff out the t-shirts any of the three times. This suggested that the people'es scents changed more when they were stressed in those with the short version of the gene. This could be why dogs can find some people better than they can find others. I find it very interesting that the dogs could not identify the people who had the short version of the gene. This could definitely be a major problem if police dogs are trying to find a criminal, so I guess we can only hope the criminal has the long version of the gene.