A STAR is born at least according to a psychologist named Jonathan Cheek. 
STAR is an acronym that stands for Social, Thinking, Anxious, and Restrained. Cheek has discovered that introverts are actually on a spectrum and believes they are often misunderstood. Introverts fight the stigma of having a behavioral defect due to a central idea that if you’re not social then there is something wrong with you. Others think that they are introspective and thoughtful, but what if none of these categories captures you? How stifling it would feel for them.
Each category describes a different type of introvert. Social introvert refers to individuals who prefer socializing with smaller groups as opposed to larger groups. Th
ey are also known to crave solitude but not out of shyness or anxiousness. Thinkers have no aversion to social gatherings and are marked as being thoughtful, self-reflective, and introspective type. Anxious introvert do seek solitude because they fight feelings of awkwardness and being around people triggers feelings of self-consciousness. The rumination behavior that goes with this type of introvert can become a barrier for them. Finally restrained introverts are reserved and often think before they speak.
Cheek’s model expands the definition of what it means to be an introvert. I applaud his work because I believe every category needs expansion. In my practice clients often find new layers to their concerns or awareness. The more one can add to the category of introspection the richer our lives become.
Source: http://nymag.com/scienceofus/2015/06/apparently-there-are-four-kinds-of-introversion.html