<i>Behavioral lateralization is not</i>

While dogs are increasingly researched in studies measuring brain activity, their paw preference (analog of human handedness) has not yet been examined in relation to electroencephalogram (EEG) spectrum asymmetry during sleep. We investigated the connection between behavioral asymmetry and sleep characteristics in family dogs for the first time, based on dogs’ behavioral lateralizations shown in different behavioral tests and dogs’ EEG characteristics during sleep. Corroborating previous results, we have found individually highly variable behavioral lateralization in dogs’ behavior depending on the task, and without population-level behavioral asymmetry in any of the tasks. However, dogs were more likely to show side preference in a two-way choice task than to use their paws laterally in different behavioral tasks. We found no significant correlations between dogs’ behavioral lateralization and EEG spectrum asymmetry in the first sleep cycle’s non-rapid eye-movement sleep or the first sleep cycle’s macrostructure, with many of our results being individually significant. We suggest that these results may be related to dogs’ highly variable and inconsistent behavioral lateralization patterns that do not have a pervasive local sleep effect, but non-exclusively, our results might be suggestive of underlying connections between behavioral asymmetry and sleep that warrant further investigations on larger samples.