Tests of olfactory memory in dogs and humans

Abstract

Olfaction is a highly evolutionarily preserved cognitive process in the brains of animals. In the fields of psychology and neuroscience, research on olfaction has lagged far behind that of vision or other physical senses. Recent evidence suggests that decline in olfactory functioning is linked to diseases such as COVID-19, diabetes, and dementia. Outside of medical issues, dogs are relied on in societies all over the world for their olfactory abilities. Dogs serve as detection dogs trained to search for narcotics, explosives, and human remains. While advances in the study of olfaction have elucidated the neural mechanisms of olfaction, the understanding of olfaction from a cognitive perspective is also important, especially the processes governing olfactory memory. This dissertation explores methods for examining olfactory memory and the influence of proactive interference in dogs and humans. Chapter 1 is an introduction that describes recent research regarding olfaction and explains why a comparative approach is useful. Chapter 2 presents two experiments that examine how proactive interference affects dog performance in an olfactory matching task. We found that dogs perform worse on tests of olfactory memory when there is greater proactive interference as a function of repetition, as well as when the source of interference was from the immediately preceding event. Chapter 3 reports two experiments that examine human memory for olfaction. In the first experiment, participants demonstrate high accuracy for olfactory stimuli after a 30-s delay indicating memory for odors lasts at least 30 s. Participants then rated each odor in terms of intensity, verbalizability, familiarity, and pleasantness. These ratings were used to select odors for Experiment 2 by selecting odors that were all at the top of the range of ratings for each category. Experiment 2 explores how proactive and retroactive interference affect human recognition of a serially presented list of odors. Results demonstrated mixed evidence of a primacy to recency shift. These studies represent an important step in understanding how memory processes can affect olfaction. Chapter 4 is a general conclusion that states the significance of this dissertation.