Besides the genetic effects on temperament, there are many things to look at in the postnatal environment. How a foal actually behaves, reacts, or displays a personality might start with genetics but is plastic and depends on his experiences. | Photo: Anne M. Eberhardt/The Horse

A: It’s really interesting to observe similarities and differences in a mare’s foals over the years. As I’m sure you’re aware, many things can contribute to a foal’s demeanor.

We know genetics play a role in behavior and temperament traits. I should say we know this in broad terms, most obviously in the general temperament differences we see among breeds of horses. We haven’t really fine-tuned the heritability of specific temperament traits in a family line of horses quite as well as we have certain physical traits. Plus, the behaviors that we can best measure that help us understand temperament are going to come from the expression of not one but multiple genes as well as the influence of the external environment and experience.

Scientists are learning that gene expression is influenced even by the cellular environment. So metabolic things that occur in an individual, even prenatally, can affect how genes act to produce the physical and behavioral phenotypes we can see