CHAPTER 2
Why Do You Have  
These Fears?
BIOLOGICAL FACTORS
As with any emotion or personality trait, our biology affects the tendency to experience 
anxiety in social situations (Mathew and Ho 2006). Biological processes such as natural 
selection or evolution, genetics, brain activity, and alterations in the levels of certain 
neurotransmitters in the brain may all contribute to social anxiety. We’ll discuss each of 
these in this section.
Natural Selection: The Evolutionary Function of  
Social Anxiety
Natural selection is the process by which members of a species who are best able 
to adapt to their environments are the most likely to reproduce successfully, thereby 
causing the species to evolve gradually and to survive over a long period of time. It 
makes sense that through natural selection, those among us who are most ﬁt and healthy 
might be more likely to survive and to reproduce than those who are less so. However, 
several authors have argued that many of the illnesses  from which humans suffer may also