Smelling more or less: Investigating the olfactory experience of the domestic dog

The performance of tracking dogs and drug-, disease-, and explosives-detection dogs is a testament to trained dogs' olfactory acuity. The olfactory experience of an untrained dog, by contrast, has not been well documented. In the current research we begin to remedy that by testing untrained pet dogs' olfactory perception of quantity. While previous research found that dogs could discriminate visible quantities of more or less food (Prato-Previde, Marshall-Pescini, & Valsecchi, 2008), our results find that, by contrast, companion dogs do not reliably discriminate quantities when the food can be smelled but not seen. Sixty-one percent of dogs (39 of 64), given a choice between closed plates with one and five morsels of food, approached plates with the larger quantity: not significantly more than approached plates with the lesser quantity (binomial, p=.169). We did find that during dogs' initial investigation of both food amounts, subjects gave more attention to the plate containing the larger quantity (binomial, p <0.001). In a second condition, we replicated, with closed plates, Prato-Previde et al.'s (2008) finding that owner interest in a plate holding a lesser quantity of food reliably leads dogs to approach that plate (binomial, p <0.001). Though research has demonstrated dogs' preference for a larger amount of food (Ward & Smuts, 2007), in a third condition testing the effect of adding a strong odor to a visibly larger food quantity, we found that the addition of odor often reversed that preference (44/69 dogs; p <.03). Finally, we consider the methodological implications of this work on future dog cognition studies. (C) 2013 Elsevier Inc. All rights reserved.