Do atheists believe in the existence of friendship?

[KerimF]

But specifically, it is dopamine, serotonin, and oxytocin (mostly oxytocin) responsible for trust.

In this case, I bet those who can have these chemicals in their body are rare on earth.

No, those chemicals are in everyone's brains.  They're neurotransmitters.  Our brains function electrochemically, and our moods and emotions are literally chemical reactions.  The levels of the neurotransmitters in our brains can be high or low, and can be influenced by genetics, by environmental factors such as stress, and by pharmaceuticals (e.g. dopamine agonists, SSRIs or intranasal oxytocin).

Oh My... Scientists proved that they are also preprogrammed to trust each other at work (thanks to some chemicals planted in their brains) much like robots which could be made and programmed to trust and work together on a certain project.

Soon I will hear that if someone opposes his instincts of survival and doesn't defend himself while he has all the means to destroy his attackers, he is driven to do so by certain chemicals planted in his brain. 

I think I have now a clear picture on why a person becomes an atheist or theist... It is all about chemicals. Some of them make atheists and many others make the various types of believers. It is indeed a very nice picture which explains all what we see in the world.