The chalky red pills manufactured by Med-Tek were a popular recreational (party) drug before the Great War, favored by consumers for their effect on creativity. The active ingredient is a powerful nootropic that increases memory related functions, and speeds other mental processes. Of course, the effect is temporary, leaving the user tired and sluggish once it wears off. Excessive consumption could also result in health complications, including migraines and even debilitating neurological disorders. Coupled with a high addiction rate, Mentats were a double edged sword.
Despite that, chem packages (available both as cardboard packs and tins) sold well, to the point where the company started developing flavored varieties with slightly different properties. Their popularity survived the Great War and made them a popular drug across the wasteland. Some chemists even figured out how to iterate on the design and create special blends of Mentats.
Mentats in the Mojave Wasteland have similar base effects to those found in New California, but differ from the ones found in The Capital Wasteland. In comparison to the Capital Wasteland variant they grant a Charisma bonus, but give significantly smaller bonuses in Intelligence and Perception. This Charisma bonus arguably makes them better than alcohol in terms of benefit, although without the Strength boost, the low addiction rate and the fact that Mentats are much less common than alcohol.
While the Mentats of Fallout: New Vegas still give a +2 Intelligence modifier, the bonus only translates into a +4 bonus to related skills like Medicine.
It is also possible to craft Mentats into Party Time Mentats, with the addition of a few extra ingredients. Party Time Mentats confer an augmented +5 bonus to Charisma, in addition to the effects of standard Mentats. However, Party Time Mentats also have a drastically decreased effect time of 1 min, a 75% decrease from standard Mentats.
Mentats are a little more rare than other drugs, but can be found on most doctors in the game.
With the Old World Blues, Mentats are extremely common in the Big MT and may be found in large quantities, especially in the Forbidden Zone. This is especially evident when entering Dr. Mobius's room in which around 60 Mentats can be found lying around, implying his mentat addiction.
Berry, Orange, and Grape Mentats are also present in the Fallout: New Vegas game files but remain unused in-game. There are signs they were meant to return as all three flavored variants appear on the list of items banned by Caesar's Legion.
Originally in Fallout, Mentats were supposed to be taken intravenously with a syringe: the .frm file for this item still exists in the Fallout Demo files.
Their name is a reference to Frank Herbert's Dune, where, in the wake of humanity rejecting artificially intelligent computers and robots, Mentats are humans trained for computer-like mathematical and logical computations. Additionally, the pills are colored red — red-stained lips are a distinguishing characteristic of a Dune Mentat.
↑Fallout 2 Official Strategies & Secrets p.74: "This party drug was once favored for the boost it gave to creativity—tune in, turn on, drop out. Mentats are just the ticket when you need to figure out something particularly perplexing or impress someone with your wits and charm. Mentats also sharpen your Perception, which greatly enhances long-range sniping attacks."