Olfactory discrimination and generalization of ammonium nitrate and structurally related odorants in Labrador retrievers

Abstract

A critical aspect of canine explosive detection involves the animal's ability respond to novel, untrained odors based on prior experience with training odors. In the current study, adult Labrador retrievers (N = 15) were initially trained to discriminate between a rewarded odor (vanillin) and an unrewarded odor (ethanol) by manipulating scented objects with their nose in order to receive a food reward using a canine-adapted discrimination training apparatus. All dogs successfully learned this olfactory discrimination task (≥80 % correct in a mean of 296 trials). Next, dogs were trained on an ammonium nitrate (AN, NH4NO3) olfactory discrimination task [acquired in 60-240 trials, with a mean (±SEM) number of trials to criterion of 120.0 ± 15.6] and then tested for their ability to respond to untrained ammonium- and/or nitrate-containing chemicals as well as variants of AN compounds. Dogs did not respond to sodium nitrate or ammonium sulfate compounds at rates significantly higher than chance (58.8 ± 4.5 and 57.7 ± 3.3 % correct, respectively). Transfer performance to fertilizer-grade AN, AN mixed in Iraqi soil, and AN and flaked aluminum was significantly higher than chance (66.7 ± 3.2, 73.3 ± 4.0, 68.9 ± 4.0 % correct, respectively); however, substantial individual differences were observed. Only 53, 60, and 64 % of dogs had a correct response rate with fertilizer-grade AN, AN and Iraqi soil, and AN and flaked aluminum, respectively, that were greater than chance. Our results suggest that dogs do not readily generalize from AN to similar AN-based odorants at reliable levels desired for explosive detection dogs and that performance varies significantly within Labrador retrievers selected for an explosive detection program.

Decoding Odor Mixtures in the Dog Brain: An Awake fMRI Study

“…In addition, the dogs' 579 perception of the mixture stimulus in our study suggest that dogs perceive the mixture as a new 580 odor rather than as its individual elements. Consistent with previous behavioral studies, this 581 may explain why dogs trained on individual target odors have difficulty generalizing to mixtures 582(Lazarowski & Dorman, 2014;Lazarowski et al, 2015). Further, dogs' brain activations showed 583 more similarity between the mixture of odors and a no reward odor, suggesting either a584 learned association or a neural bias toward the no reward (distractor) odor.…”

Thromboelastographic monitoring of the effect of unfractionated heparin in healthy dogs

“…The dogs initially took part in an olfaction study. Details of that study, including housing and husbandry, have already been published . The median weight of the cohort was 26.2 kg (range: 24.2–28 kg).…”

Improving wildlife detection dog team selection and training

“…Within breed variation is commonly highlighted in the literature (Björnerfeldt et al 2008;Barnard et al 2017), including within breed variation for odour discrimination ability (Lazarowski et al 2015). Our results also demonstrated that individual variation was prominent in all breeds.…”

“…The large degree of individual variation within breeds, both during training and accuracy testing, was not anticipated. Previous studies have highlighted the degree of individual variation within breeds (Björnerfeldt et al 2008;Barnard et al 2017), including their odour discrimination ability (Lazarowski et al 2015). Due to this study's small sample size, however, broad conclusions cannot yet be drawn on specific dog breed's trainability or working suitability.…”