His initial visual methodology has been discounted as subjective and largely discredited, but later formulaic variations of the methodology, developed by his original research assistant Barbara Heath, and later Lindsay Carter and Rob Rempel are still in academic use.
Metodologi visual awalnya telah diperhitungkan secara subjektif dan sebagian besarnya dihilangkan, tetapi variasi formula metodologi yang kemudian, yang dikembangkan oleh asisten peneliti aslinya yaitu Barbara Heath, dan kemudian Lindsay Carter serta Rob Rempel masih dalam penggunaan akademis.