Dogs (Canis familiaris) Use Odor Cues to Show Episodic-Like Memory for What, Where, and When

Episodic-like memory is a personal memory that contains what happened, where it happened, and when it happened. Although episodic-like memory in nonhuman animals has been shown using what-where-when memory paradigms, it has not previously been shown in dogs. Dogs are an excellent candidate for developing translational models of neurodegenerative disorders related to episodic memory, including Alzheimer's disease. Dogs were tested in experiments that involved spatially and temporally unique sequences of odor stimuli to see if they remembered the odors, their locations, and their times of presentation. By choosing the earlier exposed odor on two-choice tests, dogs showed the ability to encode what-when, where-when, or what-where-when memory. Further tests revealed that dogs performed optimally when all three components of what-where-when memory were available for encoding and could flexibly use this information on unpredictable tests. Although the experiments reported here show that dogs remembered what, where, and when, they did not indicate whether these components were part of an integrated single memory or were retrieved from separate files. Evidence on the question of integrated memory requires trials on which all three components are tested.