I read on the Don't Starve Wiki that you receive a sanity boost from a pig in close proximity up to +25 sanity/minute. But, it doesn't say if having multiple friendly pigs multiplies the effect.
So far, I've discovered that by befriending 3 or more pigs, it keeps several of them close to my side while chopping the same tree. This minimizes the distance between me and any of the pigs.
But, am I multiplying the sanity boost beyond +25/min by keeping more than one pig around me or just getting it closer to +25/min?