I've seen an analysis of the phenomenon where the four elements correspond to 4 major neurotransmitters, with the traits associated with having a lot of one ele

I've seen an analysis of the phenomenon where the four elements correspond to 4 major neurotransmitters, with the traits associated with having a lot of one element being pretty close to having a lot of the corresponding neurotransmitter. Maybe there really is a potentially useful means of categorizing people there.