Unlike computers, however, Mentats are not simply calculators. Instead, the exceptional cognitive abilities of memory and perception are the foundations for supra-logical hypothesizing. Mentats are able to sift large volumes of data and devise concise analyses in a process that goes far beyond logical deduction: Mentats cultivate "the naïve mind", the mind without preconception or prejudice, similar to the contemporary practice of Zen, that can extract the essential patterns or logic of data, and deliver useful conclusions with varying degrees of certainty. They are not limited to formulating syllogisms; they are the supreme counselors of the Dune universe, filling roles as menial as archivists and clerks, or as grand as advisors to Emperors.
A Mentat's capabilities can be greatly increased by taking sapho juice, but using it leads to addiction. Sapho is extracted from the root of the Ecaz tree and its use doubles or even triples the Mentat's already immense processing power. However, repeated use leaves a permanent "cranberry-colored stain" on the user's lips.
Being a Mentat can be a profession in itself, or the discipline can be added to other roles. Only a small number of people have the ability to be a Mentat; thus, those with the discipline are prized in whatever role they choose. There are also varying degrees of ability. In Dune, Thufir Hawat is considered to be one of the best mentats known at the time. Paul Atreides is a Mentat duke (and later emperor) in Dune, and in Heretics of Dune and Chapterhouse Dune, Miles Teg is a Mentat bashar (or general) and the most formidable military commander in the known universe. In Dune Messiah, Duncan Idaho is recreated as a ghola, and trained as both a Mentat and as a Zensunni philosopher; he then serves Paul as the House Weapons Master. In Children of Dune, he marries the Regent, Paul's sister Alia, but is then instrumental in protecting the royal heirs from her, demonstrating that Mentats are rarely simply disinterested observers and counselors.
It is also possible to vary the discipline: In Dune, the Tleilaxu create 'twisted Mentats' for the Baron Vladimir Harkonnen (Piter de Vries being the most notable example). These are sociopathic Mentats free from the usual constraints of human morality or instinctual considerations (de Vries is, among other things, a sadist and acts as torturer for the Baron). In Heretics of Dune the Duncan ghola supplied to the Bene Gesserit by the Tleilaxu has been altered in many subtle and hidden ways by the Tleilaxu, including the addition of submerged Mentat abilities.
In God Emperor of Dune, Leto II outlaws the order and crushes any renegade training schools he finds. Unlike his execution of historians for the purpose of controlling his legacy and symbolism, Leto never explicitly mentions why he suppresses Mentats, leaving the reader to conclude that it simply plays a role in his larger purpose of oppressing humanity in order to create his Golden Path. The art is not eliminated, however, surviving through underground schools; notably, the Bene Gesserit preserve the art, assuming that Leto knows of this (through his prescience) and approves.
I went to Wallach IX at the Tyrant's command ... My orders were to suppress the Mentat school you thought you had hidden there ... I, a Mentat, forced to suppress a school that trained people the way I was trained. I knew why he ordered it, of course, and so do you.
Bellonda retrieves the following information from Other Memory:
Order of Mentats, founded by Gilbertus Albans; temporary sanctuary with Bene Tleilax who hoped to incorporate them into Tleilaxu hegemony; spread into uncounted "seed schools"; suppressed by Leto II because they formed a nucleus of independent opposition; spread into the Scattering after the Famine.
To his own surprise, Erasmus also develops an attachment to the boy; when Gilbertus is about 20 years old, Erasmus performs a life-extension procedure on him without permission from Omnius. Because of Gilbertus' remarkable memory-organizational ability and capacity for logical thinking, Erasmus nicknames him "Mentat," created from the words mentor, mentee and mentation. During the Battle of Corrin, Erasmus deactivates an explosive trip mechanism in the thinking machine defenses in order to save Gilbertus, thereby dooming the entire machine empire. Afterward, the robot declares:
Perhaps when all the thinking machines are gone, you can teach your fellow humans how to think efficiently. Then all my work will not have been for nothing. — Dune: The Battle of Corrin
Thus, ironically, the Thinking Machines are retconned as the creators of the Mentats, who remained the Machines' enduring legacy to human civilization. Amidst the fanatical anti-computer culture that took permanent root throughout all humanity, the Mentats thrived from being an accepted substitute over intelligent technology, with the Mentats' actual origins completely unknown to all humans.
This mantra is a creation of Lynch and does not appear in the books, though in Dune there is mention that Thufir Hawat has cranberry-stained lips from sapho juice.
Mentat was the name of a 4-issue Spanish comic-book series published by Planeta-DeAgostini's Línea Laberinto in 1996 and 1997. Written by Francisco Pérez Navarro with art by Javier Pulido, it dealt with super-powered people (but not super heroes). The series was acclaimed by the national critics, but the poor sales of Laberinto precluded a possible sequel.
"Mentat" appears as a kind of master of psychic manufacturing in the John Ringo Novels Sister Time and Hero. In Sister Time it is referenced as having been drawn directly from Dune.
In Zak Penn's film The Grand, one of the characters repeats the Mentat mantra before drinking his protein beverage.