Some horses can be found cribbing. Cribbing is when a horse hooks its front teeth on wood and sucks in air. The horse can be known for getting "high". Cribbing is not a natural behavior but rather a compulsive habit. It develops as a result of boredom or anxiety or a combination of the two; although not all bored or anxious horses develop this habit. It is most often seen in horses which are kept in their box for long periods and who consequently lack mental stimulation.  

There have been claims that if a horse cribs, other horses will sometimes watch and eventually copy the behaviour, becoming cribbers themselves. These claims have been neither proven or disproven. However, if true, it is another reason for treating and curing this behavior as soon as possible.

Some people also claim that pain (e.g. from colic or ulcers) causes cribbing. These claims are based on the observation that horses that crib have a higher frequency of colic and ulcers than the normal horse population. Although analysis of various cases confirms the observation, the research suggests an alternative explanation: horses that have an unnatural feeding regime (e.g. grain rather than pasture, 1 or 2 feeds per day rather than multiple) are more likely to get ulcers or colic and are also more likely to develop cribbing due to the associated lack of mental stimulation. In other words, colic does not cause cribbing and cribbing does not cause colic, but both can be caused by unnatural feeding.