Side bias behaviour in dogs (Canis familiaris) is influenced by task complexity.

Side bias is often reported in canine cognition experiments when dogs' behaviour is tested in two-way choice tasks. Recently it has been proposed that side bias, which remains consistent over time and across different situations, may parallel a human psychiatric condition known as visual neglect. Here we tested an additional factor that could contribute to the development of side bias behaviour in dogs: task complexity. Subjects were tested in a series of two-way choice tasks of varying difficulty and the proportion of subjects showing side bias was compared across these tasks. Results showed that dogs were more likely to develop side bias in more complex situations, such as the food preference task, or in more unusual tasks, such as elbow pointing, compared to simpler tasks like sustained pointing. This suggests that, as expected, task complexity contributes to dogs' side bias, with side preference potentially being at least partly triggered by more challenging tasks that yield decreased reward.