It can be objectively stated that Humanities is the best skill in the game. Both Paranormal and Anti-Paranormal builds train humanities, as Paranormals have their Mentality increased by having ranks without hindering their Paranormal abilities, thus allowing them to use them more often. Anti-Paranormals benefit considerably from the use of FOCUS SELF, which causes their roundtime for all actions to be reduced, allowing them to train more skills in less time.
It is negatively affected by head wounds.
At 500 ranks of Humanities, and nothing else, you will have 66 Mentality points.