How do traits work in Betrayal At House On The Hill?
Mechanically, "Gain 1 Sanity" means move up 1 position on your Sanity track; this may increase your actual Sanity statistic (how many dice you roll) by 0, 1, or 2 depending on your character and previous position. This allows for greater variety in the characters than would be possible if all the tracks increased 1 point per position. It gives the players varying incentives and can also be used to flesh out the thematic/roleplaying part of the game - for example, one character feels a nervous breakdown coming on (next Sanity decrease -2) and is hiding from the scary ghosts at all costs; another is about to make a para-scientific breakthrough (next Knowledge increase +2) and really wants to confirm a few last facts in the Library. It can also encourage more cooperative interaction between the players, since an item that offers e.g. +2 Sanity will increase players' actual dice rolled by different amounts so may be worth trading to whoever gets the most actual benefit from it.