As an insular language par excellence, Sardinian is considered the most conservative Romance language, as well as one of the most highly individual within the family; its substratum (Paleo-Sardinian or Nuragic) has also been researched. A 1949 study by the Italian-American linguist Mario Pei, analyzing the degree of difference from a language's parent (Latin, in the case of Romance languages) by comparing phonology, inflection, syntax, vocabulary, and intonation, indicated the following percentages (the higher the percentage, the greater the distance from Latin): Sardinian 8%, Italian 12%, Spanish 20%, Romanian 23.5%, Occitan 25%, Portuguese 31%, and French 44%. The significant degree to which the Sardinian language has retained its Latin base was also noted by the French geographer Maurice Le Lannou during a research project on the island in 1941.