Thank you for this post, Little Jane! I was planning on asking the same question a few weeks back and forgot...I've been quite curious for some time to understand what the consensus is regarding this issue or perhaps various basic theories if there is no "one perfect answer"...
I've heard, as well, that it is an indicator of one of three things:
°Dissatisfaction with what the horse is being asked to do, either due to said horse being mentally ill-prepared for the task, or physically disliking the task,
°Excessive flies/environmental irritants to which horse is hyper-responsive.
Which, if any, or all, are correct, or what other theories do you guys have?
Thanks, OP! Sorry I didn't have any answers, only more questions!
"I'm too busy working on my own grass to notice if yours is greener"