Asymmetry of behavioral responses to a human approach in young naive vs. trained horses

The aim of this study was to investigate the impact of training experience on young horses (Equus caballus)' lateralized responses to an approaching human. The results show that the one year old untrained horses display asymmetrical responses to an approaching human, with more negative reactions (escapes, threats) when approached from the left side, while approaches towards the right shoulder elicited more positive behaviors. On the contrary, two years old trained horses reacted equally positively to approaches and contact on both sides. Our findings support those of previous studies investigating a link between emotionality and laterality and confirm the role of the left hemisphere in the processing of novel or negative stimuli. Moreover, the data underline the impact work and training can have on this laterality in horses.

Research highlights► Young, untrained horses show more negative reactions when approached by a human on their left side. ► Young horses also display more positive behaviours when touched on the right shoulder, as compared to the left one. ► Positive training can lead horses to accept approach and contact on both sides.