Answer:
Instinct theory is derived from our biological make-up. We've all seen spider's webs and perhaps even witnessed a spider in the tedious job of creating its home and trap. We've all seen birds in their nests, feeding their young or painstakingly placing the twigs in place to form their new home. How do spiders know how to spin webs? How do birds now how to build nests?
The answer is biology. All creatures are born with specific innate knowledge about how to survive. Animals are born with the capacity and often times knowledge of how to survive by spinning webs, building nests, avoiding danger, and reproducing. These innate tendencies are preprogrammed at birth, they are in our genes, and even if the spider never saw a web before, never witnessed its creation, it would still know how to create one.
Humans have the same types of innate tendencies. Babies are born with a unique ability that allows them to survive; they are born with the ability to cry. Without this, how would others know when to feed the baby, know when he needed changing, or when she wanted attention and affection? Crying allows a human infant to survive. We are also born with particular reflexes which promote survival. The most important of these include sucking, swallowing, coughing, blinking. Newborns can perform physical movements to avoid pain; they will turn their head if touched on their cheek and search for a nipple (rooting reflex); and they will grasp an object that touches the palm of their hands.