Why is it human instinct to scream yell and more when scared?

Question

Like if a random stranger touches us we either kick, scream, run flinch or whatsoever. What is the reason for those reflexes

Answer 1

To protect ourselves or call out for help. we don't want to just go blindly and screaming might throw the 'attacker' off balance.  

Answer 2

These reflexes are called "instincts" as you said, and we have evolution to thank for any instincts that we may possess.

Over the course of evolution, certain human behaviors were naturally selected (to keep) because they contributed to the ultimate survivability of the species. Here's an example:

Imagine a group of people that live in a forest with dangerous beasts, and imagine that a group of two men and two women from this larger group encountered a tiger. One man and one woman took off running the second they saw the tiger, and they got away. The other couple tried to fight the tiger off with sticks and rocks, and they ended up as a tasty snack.

If the the man and woman who ran away decide to have a child, there's a good chance that their child will be a runner when it comes to live-and-death encounters. The other couple died, so they can't have children and their instincts die with them.

This is a crude illustration of how evolution selects for traits that help us survive. The couple's instinct was to run when they saw the tiger, which helped keep them alive. In turn, instincts that help keep us alive stay in the gene pool.

Answer 3

Nothing. I mean, nobody really knows, right? It just happens.

Answer 4

When we get scared, multiple signals go through our brain.Our brain is made to withstand a certain amount of signals.When the brain is blocked with multiple signals (e.g. breathe, keep heart beating, digestion) and then more come, its like it lags(or overflows with signals) and has to refresh.That refresh means:Empty Lungs

                                            Blink Eyes

                                            Release Tension On Muscles

                                  or even stop heart from beating (Although no deaths from fear have been reported apart from elderly people)

That is why we scream, drop what we hold, do sudden moves e.t.c.

                  I hope i helped.

Answer 5

Because when your scared you might be in danger and most likely you are not in danger all the time so you don't know what else to do execpt kick, scream, etc.

                                                                                  KrisL

Answer 6

The sreaming alerts others in the family group to any danger, kicking uses the most powerful offensive muscles that we have, running is obvioulsy to get away from the danger, and flinching is bracing oneself and possible getting out of range of attack.