Pigs like to play. They're smart. They have good long-term memories, and they can be socially manipulative with other pigs. They can tell which people are nice to them and which aren't. They're also able to distinguish between pigs they know and pigs that are strangers.
Does all of this sound like it might have implications for bacon lovers? If so, that's no accident.
A paper published in the latest issue of the International Journal of Comparative Psychology surveys the existing peer-reviewed scientific literature to round up what we know about pigs' inner lives.
Authors Lori Marino, a neuroscientist and founder of the Kimmela Center for Animal Advocacy, and Christina M. Colvin, a professor at Emory University, note in their paper that pigs have been found to be mentally and socially similar to dogs and chimpanzees.
"What is known suggests that pigs are cognitively complex and share many traits with animals whom we consider intelligent," they write in the paper, titled "Thinking Pigs: A Comparative Review of Cognition, Emotion, and Personality in Sus domesticus."
The paper was funded by Someone, Not Something, a project of Farm Sanctuary, an animal rescue organization. Someone, Not Something is an exploration of the science behind the emotions, intellect and social behavior of farm animals, with the aim of extending greater compassion and legal protection to these creatures.
This group is trying to increase the amount of noninvasive research on farm animals. The paper ends with a call for more studies.
There's another goal, too.
"Ultimately, in an ideal world people would use this information to stop eating meat," Marino told The Huffington Post. "But I think that we would be happy to just give people the information and let them make their own decisions."
We caught up with Marino by email to find out more.
How smart are pigs?
What we are trying to do with this paper is get away from the "linear scale of intelligence" that sets one species above or below another. That is too simplistic.
What we are trying to do is to get a better understanding of who pigs are. Not necessarily where they stack up against others.
But, with that said, as we compared the literature on pigs and other animals we did find that in many domains pigs are as cognitively complex as dogs, primates. This is not to say that pigs are equivalent to chimpanzees in intelligence. It is just to show that there are some very compelling reasons to regard pigs as intelligent, aware, emotionally and socially sophisticated beings.
We went to the peer-reviewed scientific literature to determine that. The objective of the Someone, Not Something project is to bring scientific credibility to our understanding of who pigs are and serve as the basis for re-educating the public about them. We hope that this review will serve as a more substantive argument for cognitive complexity in pigs.
Were there any findings that surprised you? That you think folks who aren't already immersed in the world of animal cognition might find surprising?
I found the findings on tactical deception in pigs very compelling. We are familiar with the use of this kind of perspective-taking in chimpanzees as they compete for food against conspecifics [members of the same species].
But there is evidence that we review showing that pigs, too, are Machiavellian and strategize about how to out-compete their friends in foraging situations.
I think there has been relatively little research done with pigs compared to some other animals because pigs are mainly viewed as food and as biomedical subjects. They aren't seen for the complex and fascinating beings that they are.
I know you're vegan. I myself am a near-lifelong vegetarian. So we're both disposed to be moved by these findings. What would you say to people who find out about how smart, how emotionally complex, pigs are, and still want to eat them?
I'm not sure that there is anything I can say that would convince them not to eat pigs. I hope the evidence on how aware, emotional and sensitive they are will reach some people who have the capacity to be empathic.
It seems like every year, we learn about more animals having complex inner lives. Fish, pigs. Are there any animals who you think probably don't share these cognitive and emotional traits?
The more I learn about other animals the more I am realizing that there is a common level of intelligence across all life forms with brains. Each species is a variation on a theme.
This interview has been edited for length and clarity.
Get in touch at arin.greenwood@huffingtonpost.com if you have an animal story to share!