>"Introvert and extrovert are outdated terms as meaningless as Freudian oral and anal types" That's not completely true. For one thing, there are a lot of stud

>"Introvert and extrovert are outdated terms as meaningless as Freudian oral and anal types" That's not completely true. For one thing, there are a lot of studies that have found correlations between introversion/extroversion (especially as defined by the Big 5 personality model) and behavior. That alone says that the term is not "meaningless." Just check any research journal for the keywords "introvert OR extrover big 5." Here's what seems to be happening: The tests are measuring attributes that tend to go together, but do not always go together. Either you are typically outspoken in large groups you don't know well, or your are typically reserved in such groups. That's one attribute. Either you are typically drained by social interaction, or it typically invigorates you. That's another. These two attributes are correlated closely enough that research finds results, but there are probably exceptions. Personality researchers will be the first to admit that personality is complex. One of the problems in research is that the more complex your model becomes, the harder it is to test and validate. We continue to use overly-simplistic models because they are validated by research that tells us we're measuring something; no one is claiming we're measuring it completely or perfectly. I also happen to think the author's model is overly-simplistic, but that he's correctly identified the problem.