Visual laterality in the domestic horse (Equus caballus) interacting with humans

Abstract

Most horses have a side on which they are easier to
handle and a direction they favour when working on a
circle, and recent studies have suggested a correlation
between emotion and visual laterality when horses
observe inanimate objects. As such lateralisation
could provide important clues regarding the horse’s
cognitive processes, we investigated whether horses
also show laterality in association with people. We
gave horses the choice of entering a chute to left or
right, with and without the passive, non-interactive
presence of a person unknown to them. The left eye
was preferred for scanning under both conditions, but
significantly more so when a person was present. Traditionally,
riders handle horses only from the left, so
we repeated the experiment with horses specifically
trained on both sides. Again, there was a consistent
preference for left eye scanning in the presence of
a person, whether known to the horses or not. We
also examined horses interacting with a person,
using both traditionally and bilaterally trained horses.
Both groups showed left eye preference for viewing
the person, regardless of training and test procedure.
For those horses tested under both passive and interactive
conditions, the left eye was preferred significantly
more during interaction. We suggest that most
horses prefer to use their left eye for assessment and
evaluation, and that there is an emotional aspect to
the choice which may be positive or negative, depending
on the circumstances. We believe these results
have important practical implications and that emotional
laterality should be taken into account in training
methods.