The idea behind Biological Determinism is that behavior is controlled biologically.  All animals have a preset way of behaving, instincts, and an animal’s instincts are geared toward survival.  Instincts are triggered by stimuli.  The image of a predator stimulates the animal’s instincts, which tell it to leave the area.  The stimulus of food arouses the animal, creating hunger and the desire to eat.  The stimulus of the opposite sex encourages sexual behavior, producing offspring and future generations.  The stimulus does not always have to be a complete object, but rather it may only be one aspect of an object, such as the color red, that will trigger the behavior.
     Usually when an instinct is triggered it will follow a set pattern.  The concept is called the fixed action pattern (FAPs).  However, the idea that the pattern is not fixed, but rather follows a model or set of guidelines is becoming increasing popular and is called the modal action pattern (MAPs).  This allows for minor variation in the animal’s behavior even though it is following the same pattern.
     Vacuum behavior is an unusual phenomenon that occurs after an animal’s instinct is not stimulated for an extended period of time, so the animal exhibits it anyway.  This results in the animal hunting imaginary food or having sex with your friend’s leg.