Training with Multiple Structurally Related Odorants Fails to Improve Generalization of Ammonium Nitrate Detection in Domesticated Dogs (Canis familiaris)

Abstract

A critical aspect of canine scent detection involves the animal’s ability to respond to odors based on prior odor training. In the current study, dogs (n = 12) were initially trained on an olfactory simple discrimination task using vanillin as the target odorant. Based on their performance on this task, dogs were assigned to experimental groups. Dogs in group 1 and 2 (n = 5 dogs/group; 1 dog/group were removed due to low motivation or high error rates) were trained with either two or six forms of ammonium nitrate (AN), respectively. Dogs were then assessed with a mock explosive with AN and powdered aluminum. Dogs in both groups failed to respond to the novel AN-aluminum odor. Mean success rates were 56 ± 5 and 54 ± 4% for groups 1 and 2, respectively. Overall, and individual dog performance was not statistically higher than chance indicating that dogs did not generalize from AN to a similar AN-based odorant at reliable levels desired for explosive detection dogs. These results suggest the use of authentic explosive materials, without the added complication of including category-learning methods, likely remains a cost-effective and efficient way to train explosive scent detection dogs.

Case Study: An Evaluation of Detection Dog Generalization to a Large Quantity of an Unknown Explosive in the Field

“…Although training with high quantities of the target odor could be implemented with little risk for some detection dogs (e.g., narcotics detection dog), the implementation of this training method might be particularly challenging or dangerous for explosive detection dogs. Most of the research in canine generalization has evaluated training methods to improve generalization to different variants or mixtures of the target odor [ 5 , 12 , 14 , 15 , 16 , 17 , 18 , 19 , 28 ]. However, to our knowledge, no other study has evaluated generalization to different quantities of an explosive.…”

“…The success of dogs as detectors relies on their sensitivity and ability to generalize and discriminate between similar and dissimilar odors. Olfactory generalization refers to the phenomenon where a dog produces the same response to perceptually similar odors that could share the same outcome [ 11 , 12 ]. In the field, olfactory generalization occurs when a dog alerts or shows the same trained behavioral response to variations of a target odor [ 13 , 14 ].…”

“…To increase generalization, some trainers use multiple variations of the target odorant during training. However, recent studies have found that increasing the number of AN variants used in training did not improve generalization to other variants or to a mixture of AN and aluminum flakes [ 12 , 17 ].…”

Desafíos para la inclusión estratégica de equipos caninos en seguridad y defensa en Colombia

“…La revisión de la literatura que se ha hecho al respecto incluye artículos sobre el análisis forense (Furton et al, 2015) y otros que están a la vanguardia del desarrollo de nuevas medidas de seguridad para estudiar explosivos y artefactos explosivos improvisados (Prada-Tiedemann & Rodríguez, 2016;Lazarowski et al, 2020;Dorman et al, 2021), evaluando la asociación con los perros detectores de drogas y estupefacientes, lo que puede ser útil en futuras aplicaciones en contextos reales operacionales para la fuerza pública colombiana (Ejército, Armada Nacional, Fuerza Aérea y Policía), además de los demás operadores de justicia (fiscalía y jueces).…”

Canine Olfaction: Physiology, Behavior, and Possibilities for Practical Applications

“…That also shows the influence of the method of training on the results of odor detection, with the authors concluding that dogs could not spontaneously recognize a target component in an odor mixture after target-only training. Among the elements influencing the final results of olfactory work of the sniffing dogs is the issue of an animal’s ability to respond to odors based on prior odor training [ 206 ]. In this context, Dorman et al [ 206 ] showed that dogs trained with different forms of ammonium nitrate were unable to recognize the substance with an acceptable level of success when it was mixed with powdered aluminum, with the results from some animals no different to those expected by chance alone.…”