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McGreevy, P. D., & Thomson, P. C. (2006). Differences in motor laterality between breeds of performance horse. Appl. Anim. Behav. Sci., 99(1-2), 183–190.
Abstract: This study examined the relationship between motor laterality in horses bred for different types of work and therefore different temperaments. Foreleg preference during grazing was measured in three populations of domestic horse, Thoroughbreds (TB, bred to race at the gallop), Standardbreds (SB, bred for pacing) and Quarter Horses (QH, in this case bred for so-called “cutting work” which involves manoeuvring individual cattle in and out of herds). With a one-sample t-test, TBs showed strong evidence of a left preference in motor laterality (P = 0.000), as did SBs (P = 0.002) but there was no convincing evidence for laterality in QH (P = 0.117). However, the increasing trend in left preference from QH to SBs then TBs was associated with increasing differences between individual horses within a breed. The overall preference (either left or right) increased with age (P = 0.008) and the rate of increase varied with breeds. The presence of a higher proportion of left-foreleg preferent individuals in TBs and SBs compared with QH may indicate that their training or selection (or both) has an effect on motor bias.
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Tomkins, L. M., Williams, K. A., Thomson, P. C., & McGreevy, P. D. (2010). Sensory Jump Test as a measure of sensory (visual) lateralization in dogs (Canis familiaris). Journal of Veterinary Behavior, 5(5), 256–267.
Abstract: Sensory lateralization in dogs (n = 74) was investigated in this study using our innovation, the Sensory Jump Test. This required the modification of head halters to create three different ocular treatments (binocular, right, and left monocular vision) for eye preference assessment in a jumping task. Ten jumps were recorded as a jump set for each treatment. Measurements recorded included (i) launch and landing paws, (ii) type of jump, (iii) approach distance, (iv) clearance height of the forepaw, hindpaw, and the lowest part of the body to clear the jump, and (v) whether the jump was successful. Factors significantly associated with these jump outcomes included ocular treatment, jump set number, and replication number. Most notably, in the first jump set, findings indicated a left hemispheric dominance for the initial navigation of the Sensory Jump Test, as left monocular vision (LMV) compromised of jumping more than right monocular (RMV) and binocular vision, with a significantly reduced approach distance and forepaw clearance observed in dogs with LMV. However, by the third jump set, dogs undergoing LMV launched from a greater approach distance and with a higher clearance height, corresponding to an increase in success rate of the jump, in comparison with RMV and binocular vision dogs. A marginally non-significant RMV bias was observed for eye preference based on the laterality indices for approach distance (P = 0.060) and lowest body part clearance height (P = 0.067). A comparison between eye preference and launching or landing paws showed no association between these measures of sensory and motor laterality. To our knowledge, this is the first study to report on sensory lateralization in the dog, and furthermore, to compare both motor and sensory laterality in dogs.
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