Answer:
because of the reptilian part of the brain
Explanation:
Human brain is design in two different parts. The inner and ancient part is the one that is called reptilian. This part of the brain is the responsible to act in an instinctual situation. Since this is the ancient part of human brain, it has the ability to react when the body is in front of fire, a fear, or any other danger.
In the case of the reaction that is evaluated, the brain need to do two activities, to receive the stimulus and process this stimulus to react, that is the reason, why first is the action and then the idea of how is going to act.
