In order to investigate the possibility that physiognomic characteristics might be undervalued in the process of identifying uncertain portraits, we conducted a preliminary study, collecting measurements of marble portraits, normalized by calculating ratios of various measurements. This technique is in common usage in the analysis of human craniofacial anthropometry for reconstructive and aesthetic plastic surgery. . . . Our analysis of the 25 portraits of Augustus, Caligula, Claudius and Germanicus indicates that craniofacial anthropometry is in fact of very little use in portrait identification.
Craniofacial Anthropometry of some Julio-Claudian Portraits
Unsurprisingly, these findings are consistent with Coon's belief that "[o]n the whole, the well-known sculptures of Caesar, Augustus, and others [are] not reliable from the standpoint of accurate measurement":