This is a scientific study, which is relevant to law enforcement, police dog handlers and anyone concerned with scent detection and particularly canine scent detection.
This study was conducted in 2011 at the GNR in Portugal by Roger Abrantes (PhD in Evolutionary Biology and Ethology, Ethology Institute Cambridge and special advisor to the GNR), Marco Costa Pinto (Major, Company Commander, GNR) Miguel Rodrigues (Captain, GNR) and Tiago Costa Pinto (Captain, GNR). The GNR (Guarda Nacional Republicana) is the Portuguese Military Academy trained Police.
Our goal in this study was to evaluate how handler beliefs and other environmental stimuli influenced the indications given by police detection dogs.
We tested 16 teams: eight specialists in narcotics and eight specialists in explosives. The handlers were told that two conditions indicated with a paper marker could contain the target scent. Two of the search conditions contained decoy scents (food/toy) in order to test whether they would produce indications from the dogs. The search conditions were as follows: (1) no scent, (2) paper marker (red tape), (3) decoy scent, (4) paper marker at decoy scent, (5) target scent. The last condition was our way of controlling that the dogs were adequately trained and able to detect and indicate the desired target scents.
The dogs gave 59 incorrect indications. There were more clean runs in unmarked areas. In contrast, the distribution of clean runs did not differ between runs with or without decoy scents. No difference proved statistically significant.
Our conclusion is, therefore, that the dogs indicated the target scents independently of handler beliefs and decoy scents. Handler beliefs do seem to increase the number of false positives, but not in a statistically significant way. Decoy scents do not influence the number of indications given by the dogs.
In the condition containing a target scent, only one dog failed to detect or indicate it (the youngest, a one year old Labrador). This condition produced 10 false positives. These results are statistically significant, showing that the dogs do detect and indicate target scents and the handlers make the right calls.
You can read more about the parameters and conclusions of this study here.
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