Extroverts are more responsive to high-intensity and "happy" stimuli, which may be why an extrovert gets frustrated at the less "readable" face of the introvert.
Laurie HelgoeWhen an introvert cares about someone, she also wants contact, not so much to keep up with the events of the other person's life, but to keep up with what's inside: the evolution of ideas, values, thoughts, and feelings.
Laurie HelgoeSome findings reveal extroverts as more adept at reading nonverbal cues, and attribute this to the extrovert's greater interest and experience with social interactions. Another line of research using subliminal images of facial emotion found introverts to be more sensitive to the differences, and hypothesized that this may be why introverts regulate the amount of incoming social information.
Laurie HelgoeThis is why it is sometimes hard for introverts to find words: we really hate to compromise, and words are always a compromise.
Laurie Helgoe