If you are unaware of what is termed “Rollkur” or hyperflexion of the neck, it is time you knew what has been plaguing much of Dressage and has been the subject of controversy since its inception.
Horse Talk.co.nz published a new story which talks about a new study that was performed showing that horses not only choose normal poll flexion when given a choice while maneuvering, their physiological reaction to stressful stimulation is comparatively lower when compared to their reaction while in hyperflexion.
Link : Rollkur Researchers Explore Neck Hyperflection in Horses
http://www.horsetalk.co.nz/news/2009/10/212.shtml
That article linked to this one, which I think quite relevant if you haven’t seen it.