One of the most complex and least-studied subjects involving the horse is heritability of behavior. Do horses truly inherit behavioral traits, or do these traits simply come into being as the result of environmental factors and influences? There are a couple of reasons why there are few learned answers to this question. First, it is a complex issue because a great many factors are involved in behavior patterns. Second, there simply is very little in the way of scientific research to guide one’s thinking.

It isn’t that science is unable to find answers to heritability questions involving temperament, says Katherine Houpt, VMD, PhD, director of the Animal Behavior Clinic at Cornell University. Through the years, she says, the emphasis has been on studying the heritability of other characteristics, such as speed in racehorses, rather than behavior.

Houpt believes that genetics definitely play a role in determining equine behavior. Based on studies conducted with other animals, she says, it appears that there is at least a half-and-half proposition–half of the behavior characteristics being determined genetically, and half influenced by environment.

Two negative traits that seem to be passed through equine family lines with some frequency, she says, are fearfulness and reactivity. In some cases, Houpt says, certain tendencies are breed-oriented. In addition, representatives of specific bloodlines within breeds often are more prone to manifest certain types of behavior than other bloodlines