Broca is known for making contributions towards anthropometry—the scientific approach to measurements of human physical features. He developed numerous instruments and data points that were the basis of current methods of medical and archeological craniometry. Specifically, cranial points like glabella and inion and instruments like craniograph and stereograph. Unlike Morton, who believed that a subject's brain size was the main indicator of intelligence, Broca thought that there were other factors that were more important. These included prognathic facial angles, with closer to right angles indicating higher intelligence, and the cephalic index relationship between the brain's length and width, that was directly proportional with intelligence, with the most intelligent European group being 'long headed', while the least intelligent Negro group being 'short headed'. He thought that the most important aspect, was the relative size between the frontal and rear areas of the brain, with Caucasians having a larger frontal area than Negroes. Broca eventually came to the conclusion that larger skulls were not associated with higher intelligence, but still believed brain size was important in some aspects such as social progress, material security, and education. He compared cranial capacity of different types of Parisian skulls. In doing so he found that the average oldest Parisian skull was smaller than a modern, wealthier Parisian skull and that both were bigger than the average skull from a poor Parisian's grave. Aside from his approaches to craniometry, Broca made other contributions to anthropometry, such as developing field work scales and measuring techniques for classifying eye, skin, and hair color, designed to resist water and sunlight damage.