10 Small Details You Missed In Dune
9. Mentats & The Meaning Behind The Dyed Lips
One of the consequences of destroying all computers during the Butlerian Jihad was that humans were now required to do all complex calculations themselves. This eventually led to the creation of the mentat order.
Mentats are basically human computers. They are trained and selectively bred for generations to be able to do extremely advanced calculations in their heads in an instant. They also have nearly perfect memory and a highly advanced perception which makes them valuable to military powers.
House Atreides (Paul's House) employs a mentat known as Thufir Hawat (pictured above). Like many mentats, Thufir's bottom lip is stained from his addiction to drinking sapho juice, a chemical that can greatly increase a mentat's mental abilities. His eyes are also rolled back, signifying that at this particular moment he is doing one of his mentat calculations, trying to analyze the situation from every possible viewpoint objectively and come to the absolute truth of the matter.
House Harkonnen also employed mentats but they were conditioned to ignore morality when it suited them. They were known as twisted mentats.