"what your reinforcer is, how you deliver it and where you place it all have impact on the behaviour and need to be part of the error free ease of constructing the learning, not making it harder."This notion has become prevalent with horse trainers as well and has opened my eyes to how I deliver rewards. As a result, I am trying to be very conscious of my delivery with both the different horses and the different behaviors I am rewarding.
First- the different horses: the differing sensitivities follow right through to how the varying personalities take food from my hand. While Zoe is the last horse I would put a child on, she's probably the safest horse to hand feed. Her lips are so very careful that you can hold a peppermint between your thumb and forefinger and she'll extract it without ever giving you the worry that your finger will go too. Some ponies, on the other hand, sometimes seem to think that the best way to insure they get all of what's offered is to take your hand also! Clicker training does offer lots of opportunities to work on hand feeding manners but I need to be consistent in how, where and what I offer.
The other variable is what I am rewarding. Mostly I like to ask the horses to back away from me as I feed so that they do not get reinforced for leaning or stepping toward me. This is especially critical with the lesson ponies. Kids have a tendency to protectively pull their hand back as they feed and so ponies can quickly learn to scramble after that hand so the treat doesn't get dropped. But there is also Alexandra Kurland's mantra "feed the horse where he is supposed to be". If he has barged forward, then yes, the treat should be offered back where he should have been. But if the horse is backed off for some reason, then holding the treat out to my side so he has to reach for it may be necessary (not luring the horse into position- once I have clicked, he gets treated, but he may need to reach forward for it rather than tucking his nose back for it). Or if I am rewarding a horse for a nice relaxed head down, then I might deliver the treat right to a comfortable place where his nose already is to encourage him to maintain that relaxed pose.
I have also noticed how the food and hand disappears from the horse's sight when it is under their nose. So if they are at all worried about whether or not they will get it, they can get a little grabby in desperation. As I unfold my arm to deliver the treat, I try to use that as a direction signal for the horse to follow to find the hand and treat. If the arm unfolds toward their chest, they need to rock back and tuck their nose in or step back to find it. If the arm unfolds toward their nose, they just need to use lips to find it as I present it right at their muzzle. If the less-experienced ones reach to the side toward me, they have to follow my unfolding arm back to where they are aligned with head straight in front of body.
This unfolding action is what I am most trying to concentrate on right now. I need to do it promptly but not hurriedly and be sure that the horse can clearly see where the treat is going to end up so they don't get anxious about finding it.