Reaction

Character reaction is a game mechanic in Fallout and Fallout 2. It reflects general attitude of an NPC towards the protagonist. The reaction can be good, neutral of bad.

Reaction is mostly changed by saying nice or mean things to the character by choosing appropriate dialogue options (increases or decreases reaction level by 25). For talking heads, the character's expression visibly changes.

Initial reaction
Initial reaction is calculated from multiple factors:


 * Charisma compared to the NPC's Charisma
 * Karma
 * Town reputation
 * Reputation titles
 * Presence perk and Sex Appeal trait
 * Cult of Personality perk has no effect (the corresponding code is commented out)
 * Karma Beacon perk also has no effect (its code is unused)

Characters marked as "evil" have their reaction modifiers from karma and reputation titles (except Childkiller) backwards. Slaver title's effect rather depends on what the character thinks of slavers.

Only a few characters are marked as "evil" for this purpose:


 * Den
 * Strangely, Rebecca Dyer
 * Enclave Oil Rig
 * Frank Horrigan
 * New California Republic (town)
 * Buster
 * Lenny (NCR)
 * Merk
 * Mira
 * Merk's guard
 * Oswald
 * Rawhide Saloon patrons
 * Skeeter
 * Vortis' holding center guards
 * Vortis
 * New Reno
 * Bishop's man
 * Drug dealers
 * Mordino's man
 * Ramirez
 * Salvatore's man
 * Strangely, Wright's children playing a game in front of their mansion
 * San Francisco
 * Obidiah Hakeswill
 * Strangely, Dave Handy
 * Hubologists in robes
 * Juan Cruz and Vikki Goldman
 * Lo Pan
 * AHS-7
 * AHS-9
 * Vault 13
 * Matt (Vault 13)
 * Vault 15
 * Darion's dog
 * Darion
 * Darion's personal guard
 * New Khans
 * Karla
 * Phil (Khans)

Under the hood
Under the hood, it's an integer from -100 to 100, with 25 and higher for Good, -25 or lower for Bad and Neutral for in-between. There's also

Effects
Compared to how much thought was put into the reaction system, it's severely underused. Only for very few NPCs does it affect the course of the dialogue. The most prominent effect it has on gameplay is slightly affecting barter prices.