Laterality and visuo-spatial ability in the equine: Functional measures of sport horse selection?
Authors: Murphy Jack , Arkins Sean 
Published: June 2019

Laterality in any organism or species can be manifest as morphological, sensory and functional degrees of asymmetry such as hemispheric dominance, handedness or sidedness and other motor functional behaviours and as such is equally important in equitation. The influence of the horses’ sex on both the direction and the degree of the laterality was explored within and between 4 experimental procedures in the 1st study. The findings showed that the direction, but not the degree of idiosyncratic motor preference in the horses was strongly sex-related. Male horses exhibited significantly more left lateralized responses and female horses exhibited significantly more right lateralized responses. Visuo-spatial ability is also likely to be important in the performance horse. In many species, moderate to large differences in visuo-spatial ability have been reported between the sexes, with superior visuo-spatial ability being reported in males of all species investigated to date. As no known studies had addressed visuo-spatial ability in the equine, the objective of the 2nd study, was to determine if visuo-spatial ability differed between male and female horses. The results produced the first behavioural demonstration of superior visuo-spatial ability in male horses, similar to that reported in other species. There is evidence to suggest that visuospatial ability and motor laterality are associated with cerebral hemispheric asymmetry and may be intrinsically linked. Brain development and laterality have also been associated with hair patterning, and, in a 3rd study we attempted to identify predictors of lateral bias in motor behaviour in horses. We investigated the relationship between the direction of facial hair whorl rotation and the incidence/direction of laterality in the horse. The findings suggest that direction of facial hair whorl rotation may be a useful indicator of lateralised motor behavioural preferences in the horse. We then attempted to establish if laterality was evident at birth in a 4th study, where we explored if neonatal foals exhibited lateralised patterns during and immediately post the birthing process that were correlated with their facial hair whorl patterns. The results showed a significant association between the sex of the foal and the choice of foreleg presented initially during 2nd stage parturition. Significantly more colt foals led with the left foreleg and significantly more filly foals led with the right foreleg than expected purely by random and the behaviour was correlated with facial hair whorl patterns. The findings also suggest that lateralisation in the horse is determined in utero as has also been shown in humans. Comparisons of wholly intact male and female horses are warranted as they might elucidate additional linkages between motor behaviour, visuo-spatial ability and brain organisation and development in the horse. Further research in this area could lead to more appropriate competition conditions (better fence design/construction on cross-country tracks) and so eliminate unnecessary levels of risk associated with many equestrian sports.