A test for the evaluation of emotional reactivity in Labrador retrievers used for explosives detection

The United States Marine Corps (USMC) uses Labrador retrievers as improvised explosive device detection dogs (IDDs). Of critical importance is the selection of dogs that are emotionally suited for this highly specialized application. The goal of our study was to develop an emotional reactivity test (ERT) as a screening tool for the selection of IDDs. The ERT included a series of subtasks that expose each dog sequentially to visual, auditory, and experiential stimuli with an associated grading scale used by trained observers to rate individual dog responses. In this study, 16 Labrador retrievers that met initial selection criteria as candidate IDDs were assessed using the ERT, measurement of plasma and salivary cortisol concentrations (pre- and post-ERT), and an independent open-field test of anxiety in response to sound stimuli. Based on the sum of its responses, each dog was assigned an aggregate ERT score. Aggregate ERT scores from independent trained observers were highly concordant [Shrout-Fleiss's intraclass correlation (2,1) = 0.96] suggesting excellent inter-rater reliability. The aggregate ERT scores were also negatively correlated with the dogs' scores on the open-field anxiety test (Spearman rank correlation, n = 16, r = −0.57, P = 0.0214). In addition, there were significant increases in salivary (Wilcoxon signed rank, n = 16, S = 38.5, P = 0.0458) and plasma (Wilcoxon signed rank, n = 16, S = 68, P < 0.0001) cortisol levels after the ERT, compared with baseline, suggesting that exposure to the ERT test elements produced a physiological stress response. We conclude that the ERT is a useful pre-training screening test that can be used to identify dogs with a low threshold of emotional reactivity for rejection, and dogs with a high threshold of emotional reactivity for entry into the IDD training program.