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?
Best Answer
I don't have a number for you, but I've experienced that it does in fact stack.
I had two to three pigs next to me, and I noticed that the up-arrow in the sanity circle was thicker and larger than when I just had one pig.
Adding the Top-hat or Garland to the mix made it even bigger.
I cannot gauge the exact amount per minute, though. This would actually make a great mod for someone! The ability to see the current rate of change on any of the stats.