Motor laterality in domestic dogs: does the familiarity with the handler influence the paw preference?

The term laterality refers to the preference most mammals show for one body side over the other. The aim of this study was to evaluate the reproducibility of the First-stepping test (Tomkins et al., 2010) in relation to the familiarity with the handler. Thirty-eight adult dogs (22 females, 16 males, different breeds) were tested twice in a modified version of Tomkins’ test (30 repetitions instead of 50), once with the owner and once with an unfamiliar handler, one day apart. The paw preference (PP) for each dog in both tests was determined as suggested by Tomkins et al. (2010), calculating the lateralization index and considering a significant preference for Z-scores + 1.96 (right PP). There was a low concordance between the Z-scores of the two tests (Cohens’ Kappa coefficient = 0.44). In detail, the Z-score of 14 dogs was different in relation to the familiarity with the handler: 1 dog showed a right PP with the owner and a left PP with the unfamiliar handler; 9 dogs showed a non-significant Z-score with the owner and a significant Z-score with the unfamiliar handler; 4 dogs showed a significant Z-score with the owner and a non-significant Z-score with the unfamiliar handler. Previous literature on dogs and other mammals reports that laterality is strongly task-dependent. The current findings suggest that PP may be influenced by other factors, such as the familiarity with the handler, which should be taken into account when testing animals for motor laterality