Researchers at the University of Sussex have published their research on how horses communicate [1]. It seems that they use their swiveling ears to aid in communication.

Talking to someone who is not a scientist, but has lots of experience of working with horses, said that the horse riding community knew this already. However, a scientific study was needed as anecdotal evidence is not enough.

That said, this was known about for donkey’s years*!

*Non-native speakers may find this link useful.

Link
Horses’ mobile ears are ‘communication tool’ BBC News

Reference
Jennifer Wathan & Karen McComb, The eyes and ears are visual indicators of attention in domestic horses, Current Biology , Volume 24, Issue 15, 4 August 2014, Pages R677–R679.