Hard mouth?

[stormox]

I often hear people say 'that horse has a hard mouth'. What do people take this to mean? That the horses mouth is actually damaged from harsh use of the bit? The horse needs more schooling as it ignores the aids? The horse has got so used to bad riders it simply switches off from rein aids?
If a horse has a truly 'hard mouth' and is damaged can this be felt by touch, or seen, on the bars lips or tongue?

 

[Leandy]

I always used to believe it to mean that due to harsh riding, there was damage in the nerves of the mouth (bars, lips etc) such that it didn't really feel the bit properly any more. The more experience I get however, the more I realise that I don't think I have ever met a horse which does not improve considerably with good education and riding. So I think I've come to the conclusion generally it just means one of your latter two scenarios and I'm not sure the first really exists in reality.

 

[Goldenstar]

Horses can become unresponsive to the bit due to rough riding they just learn to lean and ignore it .
Many hard mouthEd horses are not hard mouthed they are set in their necks and body’s and don’t balance them selves well , Retrain them show them theres another way and magically they have lovely soft mouths .

 

[AUB]

In my opinion, it's a horse that has been taught to ignore the signal from the bit. If you both say "go" with your legs and "stop" with your hands at the same time, the horse will have to ignore one or the other and either stop even though you're putting legs on or go even though you're using the hand brake. A horse that is "hard in the mouth" will often feel heavy on the bit and will not react to a light stopping signal.

But I also find, that most horses that are "hard in the mouth" can be taught to be soft in the mouth if one is very careful to seperate the aids, always be quick to reward with release of pressure and when the correct reactions to leg and hand have been established, with many transitions and lateral movements.