Given that an instinct is an inherited body of expert knowledge, we should be able to apply the methods of artificial intelligence to build a model of an instinct. Such a model might tell us interesting and useful things about the behavior of the critters in question, such as horses.
For those who are not familiar with these methods, here are some short, non-technical introductory readings. The field itself involves a lot of math and many of the articles linked to from these Wikipedia articles are much more technical.
Knowledge representation is the core field.
Knowledge engineering is the method for uncovering the knowledge.
Expert systems are examples of how knowledge based decision making can be modeled.
I have been involved with this stuff since I was on the faculty of Carnegie Mellon University in the 1970's. In fact I worked with some of the pioneers, especially Herb Simon, who got a Nobel prize in 1978.