Although a causal relationship cannot be inferred from these results… these findings suggest that individual differences in personality are related to meaningful individual differences in neural responses to social stimuli. (Do extraverts process social stimuli differently from introverts?)
This is a small study, but the results are interesting. Extroverts, unsurprisingly, are stimulated by images of human faces more than introverts and liable to allocate more attention to them.
American Buddhist Net 
WHAT YOU SAY CAN’T BE TRUE BECAUSE INTROVERSION/EXTROVERSION ARE TERMS USED BY ONE PERSON TO DESCRIBE ANOTHER SOME PEOPLE THINK I’M AN INTROVERT BECAUSE I MEDITATE OTHERS THINK I’M AN EXTROVERT BECAUSE I PUT MYSELF OUT THERE WHEN I RELATE TO OTHERS, SO WHAT AM I? AND WHATEVER YOUV SAY IS BASED ON YOU, NOT ON ME
Good points and I have zero argument with them. My guess is that the study will be roughly confirmed, showing that there is a type of person that responds more strongly to faces than other types. Is that an extrovert? Who knows? I do agree that extroversion/introversion are crude categories that don’t say much.