My friend's bay 148 pony Teddy has a habit of yanking his head up when he is ridden. We've had the dentist out, chiropractor (Equine) and the vet to help diagnose this. They could not define the problem's origin. Teddy does not have any optical disease causing him to see dots in the sun; this has been checked. My friend blames it on 'the sweat and the flies' but this is a misdiagnosis. I began riding him today as my friend is on holidays, and give him a good sharp slap with the whip each time he does this. He uses a rubber happy mouth bit and all tack fits perfectly. Any suggestions on how he began this habit? My friend is not firm with him and has let him do this for two years; that is a contributing factor.