All Life is Problem Solving - Karl Popper    

The human brain is the result of millions of years of adaptive problem-solving by life on this planet.  It’s been a process of accretion, not logic, so it’s not perfectly logical.  But the brain is a calculating organ, and, as an organ evolved over millenia, it calculates on both conscious and older sub-conscious levels to solve problems associated with survival.  

Obviously, association with other people has presented a successful survival adaptation for us.  But nature and social life continue to present us with problems, so we are constantly calculating, consciously and subconsciously, the potential risks, costs and rewards that various actions will present to us.