A comparative study of memory for olfactory discriminations: Dogs (Canis familiaris), rats (Rattus norvegicus), and humans (Homo sapiens).

Abstract

Disagreement has arisen in the scientific literature regarding the relative olfactory ability of humans relative to other mammals, specifically canines and rodents. A series of experiments are reported in which memory for multiple olfactory discriminations was measured in dogs, rats, and humans. Participants from all three species learned a sequence of 20 different discriminations between an S+ odor and an S− odor. Choice of the S+ odor was rewarded with food for dogs and rats and with positive verbal feedback for humans. After learning the discriminations, an initial memory test was given that involved presentation of all 20 S+ and S− pairs. A subsequent mix-and-match test was given in which each S+ odor was presented with three different S− odors. The memory tests revealed that dogs were superior to rats and that dogs and rats were superior to humans. The relatively poor performance of humans contrasts with prior findings of high recognition memory for odors followed by slow forgetting. We attribute the low accuracy of humans in our experiments to the requirement that participants had to remember the outcome associated with S+ (correct) and S− (incorrect) cues and not just their familiarity.

Dogs (Canis familiaris) use odor cues to show episodic-like memory for what, where, and when.

“…Odors were used as the “what’ component because olfaction is closely linked with emotion and memory (Aggleton & Waskett, 1999; Chu & Downes, 2000; Miles & Berntsen, 2011) and has been shown to be highly potent at evoking vivid episodic memories in humans (Adolph & Pause, 2012). In tandem with dogs’ keen sense of smell (Walker et al, 2006) and impressive olfactory memory capacity (Lo, Macpherson, MacDonald, & Roberts, 2018), olfaction serves as an ideal cue for the study of episodic-like memory in dogs. Probe tests were carried out to examine dogs’ ability to remember what, where, and when.…”

Ability of dog owners to identify their dogs by smell

“…However, recent results have suggested that human olfaction is not as feeble as previously thought, and when dealing with certain substances, humans were shown to perform as well as or even better than dogs and other mammals 5 , 6 . Further studies supported the idea of inferior human olfactory perception through the investigation of olfactory system morphology 7 , the repertoire of active genes that express olfactory receptor types 8 , 9 , and olfactory memory 10 ; however, there is enough evidence to justify the opinion that human olfaction is not as poor as previously thought 5 , 11 , 12 . The terms microsmatic and macrosmatic are nevertheless justifiable when referring to species that possess or lack olfactory recesses 13 .…”

Do that again! Memory for self-performed actions in dogs (Canis familiaris).

“…They have exhibited an ability to learn to perform a wide variety of tasks in response to external cues, from detecting and reporting the presence of drugs to aiding those with disabilities in everyday tasks. Dogs also have been trained to perform a variety of memory tasks (Craig et al, 2012; Fiset, 2007; Fiset et al, 2007; Lo et al, 2020; Lo & Roberts, 2019). Some studies suggest that dogs may also be capable of imitating actions (Fugazza et al, 2016a, 2016b, 2019; Horowitz, 2014), indicating that dogs can flexibly represent others’ past behavior and can use memories of observed actions to influence their own actions.…”