Research has already found that extroverts opt for instant gratification and focus more on the faces of others than introverts. On the flip side, introverts get overwhelmed by a lot of stimulation and pay more attention to the small details, which researchers say is connected to increased brain activity when processing visual information.
Not sure if you're an introvert or extrovert? Take this quiz: http://www.guardian.co.uk/science/quiz/2012/mar/13/quiz-are-you-an-introvert
In the study, Cornell University neurobiologists Yu Fu and Richard Depue recruited 70 people, all male freshman at Cornell, who took personality tests rating whether they were introverted or extroverted. In a double-blind procedure, some of the subjects took the stimulant Ritalin, which boosts attention by stimulating the release of dopamine. Participants then watched videos in the lab.
Subjects were then tested as to how strongly they associated the videos and lab environment to the rush of dopamine induced by Ritalin. Findings showed that Ritalin translated into reward or motivation for the extroverts, who strongly associated their environment and contexts with reward. Introverts didn't show this association, and Ritalin's effects didn't translate into reward. The researchers posit that this is because the brains of introverts weigh internal cues more strongly than external motivational and reward cues.