Many FOURs vacillate between phases of exaggerated activity and others in which they are withdrawn and quasi-paralyzed. This manic-depressive structure can in some people who are highly introverted (stronger influence of the FIVE wing) turn into an altogether depressive structure. FOURs whose more success-oriented, extroverted THREE wing is dominant are by contrast often hyperactive. These two “subtypes” of FOUR do not look very similar at first glance.9
