Intelligence

Intelligence is one of seven primary statistics in the SPECIAL system.

Fallout, Fallout 2 and Fallout Tactics
Modifies: the number of new skill points per level, numerous dialogue options, and many skills.

One of the unique qualities of Fallout and Fallout 2 is the difference in gameplay caused by creating a low-Intelligence character. With a dimwitted player character, many non-player characters will simply shrug one off, while others will insult or even attack them. On the other hand, certain characters will take pity on the character's stumped intellect, and might treat them as innocent children. In some cases, where a character with normal vocabulary would need to persuade them or offer a service in exchange, these characters will often give the character gifts or allow them entrance in certain areas for free out of pity.

Ways to increase Intelligence

 * In Fallout, the Brotherhood of Steel doctor in Lost Hills can perform an operation to permanently increase Intelligence by 1, assuming it can be afforded. The surgery can be done twice, assuming the Vault Dweller has an Intelligence below 4 the first time it is performed.
 * Intelligence can be raised permanently in Fallout 2 in three ways. First, by using ACE and the yellow memory module (+1). Second, by the Hubologist zeta scan/alignment in San Francisco (which can also provide +1 Luck, though the game may need save-scumming to get a bonus rather than a penalty). The last method is to take the Gain Intelligence Perk. The bonuses from these methods stack for a total of +3 Intelligence.
 * In both Fallout 1 and 2, it can be increased by +1 for purposes of dialogue only, by taking the Smooth Talker perk.
 * In both Fallout 1 and 2, Mentats can be used to temporarily raise Intelligence by 2.
 * In Fallout 2, Intelligence can be temporarily raised by 1 point by the Purchase the Kesting Special quest given by Miss Kitty in the Cat's Paw brothel.

Fallout 3
Modifies: Medicine, Repair, and Science skills, as well as the number of new skill points per level.

Intelligence determines the number of skill points earned per level up. The base number of skill points gained per level is 10 + INT. Skill points gained for raised Intelligence are not retroactive for past levels, so increasing this primary stat early, if at all, is the best. Also, temporary modifiers to Intelligence (e.g. from Night Person or Button's wig) do not affect the number of skill points gained when leveling up.

Ways to increase Intelligence

 * Permanent
 * Bobblehead - Intelligence (+1)
 * Intense Training perk (+1 per rank)
 * No Weaknesses perk (will raise base to 5 if below 5.)
 * Almost Perfect perk (will raise base to 9 if below 9.)
 * Temporary
 * Button's wig (+1)
 * Lincoln's hat (+1)
 * Berry Mentats (+5)
 * Mentats (+5)
 * Night Person perk (+2 between 6:00 PM and 6:00 AM)

Fallout: New Vegas
Intelligence affects skill points differently from how it did in Fallout 3. The number of skill points gained each level is based on the formula 10 + (0.5 * IN) per level, including level 1, where IN is the Courier's Intelligence. If one gets a non-whole number of skill points per level (e.g. 10.5 for INT 1) it will be saved for the next even level up (see Skill Rate).

Ways to increase Intelligence

 * Permanent
 * Intelligence Implant available at the New Vegas medical clinic (+1)
 * Intense Training perk (+1 per rank)
 * Completing the quest The Apocalypse or The End will allow raising any one primary statistic by 1.
 * Temporary
 * Only permanent increases in Intelligence will increase points received when leveling up. While traits are relatively permanent (they cannot be changed at any time like the other temporary items), they will not increase level-up points.
 * Armor and clothing
 * Mad scientist scrubs, Scientist scrubs, Dr. Klein's glasses (+1)
 * Dr. Klein's scrubs, Dr. Mobius' scrubs, Dr. Mobius' glasses (+2)
 * Chems
 * Mentats (+2)
 * Party Time Mentats (+2)
 * Perks
 * Meat of Champions (+1 for 60 seconds after eating a corpse.)
 * Night Person (+2 between 6:00 PM and 6:00 AM)
 * Traits
 * Claustrophobia (+1 while outdoors, but -1 indoors)
 * Early Bird (+2 between 6am and 12pm, but -1 between 6pm and 6am)
 * Black coffee (+2 - +6 depending on Survival skill)
 * "Smart Light" (+2 for 12 hours or until the player character uses the "Mood Lights")

Ways to decrease Intelligence

 * Temporary
 * Armor and clothing
 * Lobotomite goggles, Lobotomite mask and goggles (-2)
 * Consumables
 * Alcohol (effects do not stack)
 * Absinthe, beer, Battle Brew, Jake Juice, Rum & Nuka, scotch, vodka, whiskey, wine (-1 to -3 depending on Survival skill)
 * Irradiated beer, irradiated scotch, irradiated whiskey (-1 to -3 depending on Survival skill)
 * Moonshine (-2)
 * Wasteland tequila (-2 to -6 depending on Survival skill)
 * Large wasteland tequila (-3 to -9 depending on Survival skill)
 * Chems
 * Ant nectar (-2)
 * Ant queen pheromones, Fire ant nectar (-3)

Intelligence in quests and exploration

 * An Intelligence of 3 or less will grant "special" reverse-Intelligence dialogue and actions. The majority of instances are listed below.
 * During Come Fly With Me, one has the unique option to randomly mash the buttons on the launch control panel. The rockets will humurously take off and rewards will be gained as though one passed the 55 Science check to properly input improved coordinates.
 * When first meeting Ignacio Rivas at HELIOS One, one can respond by saying "I is scientistic" after being asked about their reasons for visiting the power plant.
 * When first meeting Ranger Milo, he refers to the Legionaries in Nelson as "Legion snakes," to which one can respond by believing he meant actual snakes trained by the Legion, rather than him clearly speaking metaphorically.
 * When first meeting Veronica, one can only humorously state they believe Brotherhood of Steel members can shoot lasers from their eyes after she asks how much one knows about them.
 * When talking to Dog, one can to ask about how he arrived at the Sierra Madre (without the use of exploits, this check must be passed to complete the challenge, The Whole Sad Story).
 * An Intelligence of 2 or less will grant "extra special" reverse-Intelligence dialogue and actions. The majority of instances are listed below.
 * When approached by the mobile facial recognition scanners on the third floor of REPCONN headquarters, one can inadvertently guess the security password and roam the area without aquiring a keycard.
 * When convincing Arcade Gannon to become a companion, one can do so out of pure sympathy, by saying that Freeside is very complicated and a smart guy like him could help do stuff.
 * An Intelligence of 6 is required to convince Joe Cobb of the benefits in taking over Goodsprings and to let the player join his gang in attacking the town, starting Run Goodsprings Run.
 * An Intelligence of 6 is required to see through this traveling merchant's facade and force him into admitting that he is a bounty hunter in disguise during I Fought the Law.
 * An Intelligence of 6 is required to offer the more convincing argument that snipers usually work in pairs when Craig Boone asks why he should join the player after completing One for My Baby. Boone can still be recruited as a companion through another standard dialogue option regardless though.
 * An Intelligence of 6 is required to explain that one understands the Brotherhood of Steel is only hostile to those who use plasma or laser weaponry around them, when questioned by Veronica about how much they know about the group.
 * An Intelligence of 6 is needed to ask Orris how he managed to kill 4 thugs with 3 shots during the G.I. Blues quest.
 * An Intelligence of 6 is required to cook the imitation strange meat pie using the recipe during Beyond the Beef.
 * An Intelligence of 6 is required to catch Frank Weathers out in his story, and make him admit to running away whilst the rest of his family was captured by Legion slavers.
 * An Intelligence of 6 is required to point out to Sergeant Kowalski there must be a connection between the sudden appearance of crop farms in Westside and the recent shorage of water from NCR pipelines during The White Wash, the point seems lost on him though.
 * An Intelligence of 6 is required to correctly accuse, and subsiquently have Tom Anderson admit to, stealing water from NCR pipelines, without having to catch his accomplice in the act during The White Wash.
 * An Intelligence of 6 is needed to ask Arcade Gannon how he knows so much about REPCONN when entering their pre-war headquarters. Passing the check will gain 1 of 5 minimum "history points" with Arcade for him to later initiate For Auld Lang Syne.
 * An Intelligence of 7 is required to clarify one's interest in HELIOS One is purely scientific when questioned by Ignacio Rivas when first meeting.
 * An Intelligence of 7 is required for one to counter Cass' wit by asking if she even knows what a fish is herself after she talks about them.
 * An Intelligence of 7 or a Speech of 70 allows the Courier to talk Alice Hostetler down from killing her mother in the quest Someone to Watch Over Me.
 * An Intelligence of 7 is required to dedue Sergeant Bitter-Root is not being truthful about what he remembers from the Bitter Springs Massacre, to which he will indirectly admit that he may have taken the oppertunity to kill some of his own fellow Great Khans during the fighting.
 * An Intelligence of 7 is required to impress Loyal, by presuming that he has planned out a diversionary stratagy for the NCR whilst the crashed B-29 is being recovered during Volare!
 * An Intelligence of 7 is required to recite an override command to the mobile facial recognition scanners on the third floor of REPCONN headquarters, allowing one to roam the area without aquiring a keycard.
 * An Intelligence of 7 is required to convice First Sergeant Aster that Private Edwards is not showing signs of becoming a feral ghoul and allow him to return to the NCR milliary.
 * An Intelligence of 7 is required to explain oneself to Arcade after killing Anderson during The White Wash. Passing the check and choosing the dialogue option which suggests Anderson's death will prevent his thieving from being blamed on the other Westside residents and will gain 1 of 5 minimum "history points" with Arcade for him to later initiate For Auld Lang Syne.
 * An Intelligence of 7 is required to convince Arcade that diverting HELIOS One's power equally across the whole New Vegas grid would be the best choice when he confronts the player after first talking to Fantastic during That Lucky Old Sun. Passing the check will gain 1 of 5 minimum "history points" with Arcade for him to later initiate For Auld Lang Syne.
 * An Intelligence of 8 is required to convince Arcade that he should not be so judgmental of Caesar's Legion because he does not know what they may have gone through. Passing the check will will gain 2 of 5 minimum "history points" with Arcade for him to later initiate For Auld Lang Syne.
 * An Intelligence of 8 is needed to trick Silus into thinking the Courier is an agent of Caesar's Legion on a mission to kill him. Silus will take the bluff and inform the Courier about Caesar's brain tumor and indirectly about Ronald Curtis.
 * An Intelligence of 5 is required to understand that Christine can slow the detonation time of your explosive collar near radios when first nearing the vicinity of one though, alluding to her companion perk, Signal Interference.
 * An Intelligence of 6 is required to understand that Christine is has a way to make counterfeit Sierra Madre chips, and subsequently be taught the technique oneself, therefore gaining the Coin Operator perk.
 * An Intelligence of 6 is required to understand why Christine has been ordered to man the Puesta del Sol switching station during Trigger the Gala Event, as Dog/God and Dean Domino lack the technical knowlage to do so.
 * An Intelligence of 7 is required to suggest that Christine could use writting to communicate when first meeting her in Find Collar 12: Christine, though she will inform the player that is not possible.
 * An Intelligence of 7 is required to impress Christine by understanding her miming a Brotherhood of Steel Smybol when first meeting her in Find Collar 12: Christine.
 * An Intelligence of 7 is required to understand the Electrical Diagram during Fires in the Sky. When God confronts the player immidiately afterwards, attempting to blackmail them into keeping him as the active personality because he understands the diagram, whilst Dog would not; one can then call his bluff with an accompanying Intelligence 7 check warning that they could order Dog through the diagram themselves if need be. Informing God of this will make him back down, agree to opperate the controls himself, and skip his usual task where he asks the player to collect ghost harvester remains.
 * An Intelligence of 6 is needed for Dr. Mobius to reveal that they are still planning how to save themselves.
 * An Intelligence of 8 is required to deduce that Dr. Mobius scattered the Sink personality chips across Big MT when talking to Dr. Klein during Welcome to the Big Empty.
 * An Intelligence of 7 is required to complete What's in a Name? for Dr. 0. A subsequent Intelligence of 9 check following the aforementioned quest is required to resolve O's name issue fully. Passing both checks will cause O to side with the player against Dr. Klein during Old World Blues, and act as 1 of the 3 required votes to make peace with the Think Tank if one tries to appeal to their humanity.

Fallout 4
Unlike in previous games, Intelligence has no effect on skills, since Fallout 4 lacks a separate set of scores for skills. Instead, a higher Intelligence—in addition to unlocking higher perks in the Intelligence category—will increase the amount of experience the player character earns from all sources.

The experience multiplier linearly increases from 103% (1 Intelligence) to 130% (10 Intelligence). In other words, it increases XP gains by 3% per INT. It continues increasing if Intelligence is brought higher than 10. In math terms:
 * $${\it XP}_{\rm Final} = {\it XP}_{\rm Base}\times \left(1 + \frac{{\it Intelligence} \times 3}{100}\right)$$

A higher Intelligence also reduces the number of words that are displayed while hacking a terminal; for example, at an Intelligence of 10 or higher with a Science bobblehead, it almost becomes trivial to brute-force most hacking sessions.

Ways to increase Intelligence

 * Permanent
 * Level (+1)
 * Intelligence bobblehead (+1)
 * You're SPECIAL! book (+1)


 * Temporary
 * Armor and clothing
 * Liam's glasses (+2)
 * Lab coat (+2)
 * Press cap (+1)
 * Road goggles (+1)
 * Ushanka hat (+1)
 * Mechanist's helmet (+1)
 * The Captain's Hat (+2)
 * Inquisitor's cowl (+1 up to +4)
 * Legendary armor effects
 * Chems
 * Berry Mentats (+5)
 * Mentats (+2)
 * Daddy-O (+3)
 * X-cell (+2)
 * Perks
 * Night Person (+2/+3 at night)
 * Settlement objects
 * Vault 88 overseer's desk (+1)

Ways to decrease Intelligence

 * Temporary
 * Armor and clothing
 * Chems
 * Dirty Wastelander
 * Beer
 * Settlement objects

Intelligence in quests and exploration

 * The Last Voyage of the U.S.S. Constitution has multiple intelligence checks that can speed up progression through the quest. Instead of replacing components, the player character can repair them instead. This strategy applies to the replacement of the wires (requiring an Intelligence of 5) and radio antenna (with a score of 9 INT).
 * When romancing Magnolia, she may compliment the player character's intelligence if the score is their highest SPECIAL attribute.
 * When repairing the decontamination system in Ablutions, an INT of 7 or higher can be used to make the decontamination arches remove radiation.

Fallout 76
Modifies: Item Condition and Durability, Ability to Hack Terminals, and Scrapping Return

Raising Intelligence decreases the number of words when hacking terminals.

At an Intelligence of 1, there is a +0% crafted item condition bonus. Each additional level of Intelligence increases this condition bonus by +5%, except for the jump from Intelligence = 4 to Intelligence = 5, where the bonus increases by +10%. At the maximum Intelligence of 15, the crafted item condition bonus is +75%.

Effects on scrapping yield
A higher level of Intelligence increases the return from scrapping items.

Ways to increase Intelligence
Note that all stat boosts in Fallout 76 are temporary.
 * Bobblehead: Intelligence (+2 for 1 hour or 2 hours with Curator)
 * Armor and clothing:
 * "Casual" underarmor with a treated lining mod (+1)
 * "Casual" underarmor with a resistant lining mod (+1)
 * "Vault suit" underarmor with a resistant lining mod (+2)
 * "Casual" underarmor with a protective lining mod (+1)
 * "Vault suit" underarmor with a protective lining mod (+2)
 * "Casual" underarmor with a shielded lining mod (+3)
 * "Vault suit" underarmor with a shielded lining mod (+2)
 * Legendary Effects:
 * Intelligence (+1)
 * Mutations:
 * Egg Head (+6)
 * Herd Mentality (+2 if grouped, -2 if solo)
 * Perks:
 * Night Person (+1 to +3 during the night)
 * Consumables:
 * Food:
 * Brain bombs (+3)
 * Brain fungus soup (+2)
 * Broiled scorchbeast brain (+3)
 * Owlet nuggets (+1)
 * Scorchbeast mixed meat stew (+1)
 * Drinks:
 * Simple aster tea (+1)
 * Steeped aster tea (+2)
 * Chems:
 * Berry Mentats (+5)
 * Daddy-O (+3)
 * Mentats (+2)
 * X-cell (+2)

Fallout Shelter
Intelligence affects how efficient a dweller is while working in the medbay and science lab facilities. A dweller's Intelligence can be increased by assigning them to the classroom.

Fallout: The Board Game
Unlike other games, Intelligence is not treated as a variable ranging from 1 to 10, but instead as a token that can be obtained at the start or when leveling up. A player character with the Intelligence token gets free rerolls during certain tests, as well as during fights if equipped with an Intelligence-based weapon. They can also recruit certain companions from the shop.

The Brotherhood Outcast player character always begins the game with Intelligence. Any player character wearing the lab coat gains one hit during an Intelligence test. During any Intelligence test, Mentats can be used to gain one free hit.

Intelligence-based perks

 * Gun Nut
 * Nerd Rage!
 * Swift Learner

Intelligence-based weapons

 * Alien blaster (x2)
 * Fat Man
 * Laser rifle
 * Plasma gun

Companions requiring Intelligence

 * Loadlifter
 * Protectron

Fallout and Fallout 2
When the player character in Fallout and Fallout 2 has less than 4 Intelligence, the biggest change in gameplay is undoubtedly the dialogue. Upon reaching Shady Sands, the villagers take pity on the Vault Dweller, and Aradesh will simply shrug them off. The best they can speak is half-word sentences or gibberish. This makes for some humorous unique dialogue with the Overseer while attempting to return the water chip.

It is possible to complete the game as an idiot, but most side quests are impossible to do, and character growth is limited, as is the story involvement possible - while it is possible to bumble through the main quests, almost all plot details and background information will be left missing. Furthermore, due to limited-at-best non-player character interaction, almost all side quests are unavailable.

Talius at the Boneyard will gift a low Intelligence character with some mentats, and Darrel at the Lost Hills bunker gives them Rad-X. Additionally, during Dr. Lorri's surgeries, a Vault Dweller with low Intelligence will fittingly receive a 50% discount on the Intelligence boosting implant, lowering the price to 3000 caps.

The only companion available to stupid characters is Dogmeat.

The real downside, though, is the nigh impossibility to do about 90% of the side quests. No one will talk to a moron or even give them the time of day.

In Fallout 2, the Chosen One may meet Torr, the "town simpleton of Klamath," who would normally give them a quest to help protect his brahmin against "the evil bugmen." If the player character has low Intelligence, however, he will appear to be highly intelligent as if being stupid has a culture and language of its own. Two flat-headed people can have a complete, thought-provoking, and fully articulated conversation between them.

Another person one may have an "intelligent" conversation with is AHS-9, who becomes able to understand what the Chosen One tries to say after the alignment, and gives the quest to kill the Shi Emperor.

At the Den, low Intelligence characters still have the option to become a Slaver, and they will still receive a reward from Becky for killing Metzger. Killing Metzger is also the only way for dim-witted characters to free Vic, and he will still be available as a potential companion regardless of Intelligence.

For idiot players, the quest Something strange is happening at the farm northeast of Modoc. Investigate and report back to Jo becomes much easier. It will be presented to them while talking with Jo at Modoc. If they agree, all they have to do is travel to the Ghost Farm and talk to Vegeir. It is followed by Deliver Slag message to Jo in Modoc. One will be rewarded with the location of the Gecko town, which Jo mistook for a G.E.C.K. They will also receive an additional reward for completing the quest Farrel has a rodent problem in his garden. Remove the infestation, a cookie.

At Vault City, Skeev will try and enslave a stupid Chosen One. If one allows it, they will trigger a brief cinematic at the Servant Allocation Center with Barkus, before being automatically transported to Vault 8. If the auto-doc in the courtyard has been repaired, then the unmarked quest Auto-Doc Rodeo becomes available. This quest gives 2 unique perks which are determined by ones Luck stat.

A stupid Chosen One will speak a unique stupid line after hitting Lumpy at Broken Hills with their Highwayman. This is interesting, as one will need to boost their Intelligence via the use of Mentats in order to purchase and repair the Highwayman first. The mutant sheriff of Broken Hills Marcus, may become provoked if insulted by a stupid character, which makes him turn hostile.

When talking to Algernon in the basement of New Reno Arms, the Chosen One can start a childhood "cop and robbers" type dialog in which they accidentally "shoot" and kill him.

"Take care of Officer Jack" for Mira is a unique quest available only to player characters with an Intelligence stat of below 4 and a Strength stat of 7 or above. Also, the quest Retrieve Parts/Gain Access to Vault 15 is still available and one can still have a somewhat normal conversation with President Tandi at the NCR town.

Gruthar allows the Chosen One to enter Vault 13 freely, after realizing that they are clearly mentally handicapped.

Low Intelligence characters are presented with an additional option when it comes to completing the Navarro quest You need to use a FOB to access the navigation computer. They can lie to the base commander's room guard after they are mistaken as clean up crew, allowing them entry to his room. Unique dialogue is also present while conversing with the sympathetic quartermaster.

A character with a low Intelligence is unable to gamble. When they observe a roulette table or a slot machine, the character will respond to it as a fun toy or an interactive character, respectively. Visiting a craps table will result in a dumb Chosen One commenting to the dealer that they "play craps in pants".

Fallout 3
In Fallout 3, there are conversation situations where characters with low Intelligence are granted other dialogue options, often relating to their low intellect. However, these options are few and far between, unlike the other Fallout games where one could play the entire game as a person without Intelligence. One instance is in Roosevelt Academy, where if the Lone Wanderer activates Dean Dewey while having an Intelligence below 4, he will deem them a "special needs" child, and escort them to a "proper room."

Fallout: New Vegas
In addition to alternative Intelligence checks, low Intelligence changes some dialogue options when speaking to vendors and non-player characters. For example, when speaking to Miguel at Miguel's Pawn Shop, the option to start trading is "Me buy things," and when speaking with Dr. Usanagi at the New Vegas medical clinic after she gives the Courier the initial description about implants they get the dialogue option "You sell plants, too?", which will cause her to re-explain the implants and suggest [the player character] take the implant to make them smarter. If taking her up on this deal, she will state that she thinks the Courier "could really benefit from it," and offer the implant at a discount.

In place of the gibberish of past games, however, the player character will simply not completely understand a conversation, confuse what someone is saying with something else entirely, or not understand what situation they are currently in. In the REPCONN headquarters, for example, a character with an IN of < 3 can bypass a robot that demands a password by saying "ICE CREAM!" Normally, a Luck of at least 7 would be needed to guess this.

Low-Intelligence characters attempting to do the quest That Lucky Old Sun will be granted several unique dialogue options when conversing with Fantastic and Ignacio Rivas. An example is when informed about the hostilities between the Followers and the NCR, the Courier can ask, "Do Flowers and NCR bear play together?"

When first speaking to Ranger Milo he will inform the Courier that some "Legion snakes" are held up in Nelson, to which they can respond "Snakes are small. Why don't you just use a gun or whatever to shoot them." He will then call them a "special folk," and explain that they are not really snakes but "like snakes."

While helping Argyll in Nellis medical station while doing the quest Volare!, the Courier is given an option to "CHOP CHOP CHOP!" instead of giving him treatment. Ironically, the Courier actually saves the patient and Argyll comments on it, saying it was "dumb luck."

In Dead Money, the Courier will say "bye-bye, light person!" upon exiting dialogue with a hologram.

If the Courier's Intelligence stat is the most extreme (highest or lowest), Doc Mitchell will either compliment saying "maybe them bullets done your brain some good" (for highest) or apologize, stating he fixed up the Courier's head the best he could (for lowest).

Fallout 76
Similar to Fallout 3, low Intelligence checks are involved in situations where characters with low Intelligence are granted other dialogue options, often relating to their low intellect. Checks range from +4 to even negative Intelligence, going from -1 to -7.