We are all familiar with the fight or flight survival instinct and an analogy commonly used for this scenario is the deer in the headlights example. Created because more often than not, when deer are crossing the road as a car is driving by, they freeze and stare into the headlights before moving and running away.
In this video, as a cross country race is underway a herd of deer run through the crowd and one deer collides into a runner.
Information and Data: Relating to the concept of perceiving motion in an environment, in this scenario the deer are alarmed by the appearing stampede of cross country runners. The motion of the runners have captured the deer's attention and has triggered the flight response. Since a deer is an animal of prey, their focus of perception is to be on constant alert for any signs of danger. According to Lennie Rue a wildlife photographer, "A deer's eye is geared to detect motion, the slightest motion, and to move while the subject is in the deer's range of vision is to ensure detection."
Assumptions: In this situation what I believe has happened was that the overwhelming emotion of fear caused impaired the deer’s vision. Focusing all of its attention on running away and staying close to his herd, it missed the detection of the runner and ran straight into him.