Odor Span Task in Purpose-Bred Detection Dogs

Abstract

Working memory is essential for organisms to solve problems related to their survival and to adapt to changes in their environment. Researchers have sought to create a non-human model of working memory that can be used to better understand its predictive value and underlying brain function. Several of these studies have been conducted using the odor span task (OST) with rodents, but domestic dogs may be more suitable. Due to the unique similarities between the aging brains of humans and dogs, a model of working memory in dogs could provide useful insight to both veterinary and human medicine. Additionally, the development of an OST in detection dogs is essential to understanding the predictive value of working memory for odors on work success. Six purpose-bred detection dogs were trained on a dog-adapted OST with 24 trials. The OST is a non-match-to-sample task in which the dogs were presented with both a novel (S+) and a previously encountered (S-) odor on each trial. A response to the novel odor was always reinforced. Upon meeting training criterion, the dogs were tested on the OST with an increasing number of odors within a session in order to evaluate working memory capacity (WMC) for odors. The dogs displayed accurate performance (80 percent correct or higher) for set sizes up to 72 odors, which suggested a capacity that is much higher than human WMC. Further analyses focused on the effect of intervening odors (i.e., the number of trials since the S- was last encountered). The dogs demonstrated above chance performance for up to 8 intervening odors, which may be a more accurate representation of dog WMC for odors.