Barbara J. King

Friday Animal Blog

On Pig Welfare, and Pets’ Effects on our Health: The Role of Science

January 7, 2011

A while ago, I decided I would start Friday Animal Blog’s New Year with a focus on scientists who study domestic pigs’ physiological responses to an enriched environment. The idea is to see if pigs who are offered cognitive challenges experience more positive emotions.

I really like the bringing together of scientific experiment and applied animal welfare, and I still want to describe the paper. But, as sometimes happens, two apparently unrelated pieces of writing have crashed into each other in my head, forcing a mental shift. That is, I’m already thinking about the pig work a bit differently after reading an op-ed by Hal Herzog on pets and human health, published three days ago in the New York Times.

Let’s start at the beginning. The pig paper is from “online first” at the journal Animal Behaviour. Titled “Autonomic reactions indicting positive affect during acoustic reward learning in domestic pigs,” it’s written by scientists at Germany’s Institute for Farm Animal Biology: Manuela Zebunke, Jan Langbein, Gerhard Manteuffel, and Birger Puppe.

Zebunke et al. took 24 young weaned male pigs, living in six different groups, and exposed them to call-feeding stations (CFS’s). A CFS is a chamber housing a feeding trough, with loudspeaker equipment inside, and a red plastic button prominently placed in a location accessible to the pigs. Each pig was assigned an individual acoustic signal; the pigs’ behavior at the CFS was recorded by computer.

At first, the red button was covered. The pigs, following a traditional classical-conditioning phase, were each “individually called by one of the CFSs to visit it and to get a portion of food as a reward.” Next, the button was uncovered; now the pig had to push the button, first once and later five times, to get the food.

As always, this peer-reviewed paper is full of precise methodological descriptions and statistical results. The upshot is this: The pigs learned quickly what to do to get food, and developed “an autonomic reaction” only to their individual sound signal. Specific measures of cardiac and physiological responses showed that the pigs were aroused in a way consistent with positive emotion. Among the authors’ conclusions are that “the pigs were in a state of affective arousal owing to reward anticipation that was probably accompanied by positive valence,” and that “adequate cognitive challenges were evaluated as emotionally positive by domestic pigs.”

I feel so conflicted about this paper. The science is rigorous, and it’s clearly motivated by intent to help animals. Yet note a line buried in the article: “After the experiment, the pigs… were fattened until slaughter weight.” I haven’t eaten a pig – or cow or lamb—for years, and don’t intend to do so ever again. Yet even vegetarians and vegans, in acknowledging the reality of meat consumption in the world today, can support efforts to make more pleasant the lives of animals raised for consumption (even while they may agitate for the stopping of meat consumption no matter how benignly the animals are raised).

There’s another perspective, though, and here’s where Hal Herzog’s op-ed of January 4th comes in. In “Fido’s No Doctor. Neither is Whiskers.” Herzog writes that it’s established in the public consciousness that pets aid our mental and physical health, yet the peer-reviewed science is keenly divided on this topic. Some data support that claim and others flatly contest it.

A 2006 survey of Americans by the Pew Research Center showed, Herzog notes, that living with a pet brought people no extra happiness; research on chronic fatigue sufferers showed that despite self-reports of fewer symptoms experienced around animals, objective measures indicated these people were just as tired and stressed as controls who lived without pets.

Herzog concludes: “The truth is that we know little about how pets could affect us biologically, or why a health benefit accrues to some people but not others. Answering these questions will require the same rigorous methods that scientists use to test the effectiveness of drugs and medical procedures.”

And there you have a link between the pig paper and the Herzog op-ed: the invocation of quantitative studies as the primary tool for understanding both animal welfare and human-pet connections. (Never mind the irony that studies already done in the latter realm are so divergent!)

Don’t get me wrong. I’m a scientist, and I welcome research in both arenas. But we should neither wait for nor insist on statistical back-up before enriching the environment of captive animals. It takes no genius to realize that animals like pigs, chimpanzees, elephants, dolphins, and ravens (and many others) will respond positively to encountering even slightly more interesting-than-usual things to do with their brains—and their time.

Similarly, we cannot reduce the mutually joyous relationship between people and animals to statistics. Nowhere in Herzog’s piece does he consider the animals’ own needs. As I put it in my letter of response to the Times:

People in caring cross-species relationships report increased life satisfaction and, by all indicators of body language and emotional expression, the animals themselves (who might otherwise languish in shelters or on the streets, or face euthanasia) gain terrific benefits.

Let’s not keep pets—or pigs—waiting for the better lives we can offer them right now.


  1. January 7, 2011 9:04 AM EST
    Of course I had to read this. The problem I have with the Animal Behaviour paper and model is that it's about, well, behaviour, which is not a great model of anything. That is, it measures responses to stimuli, rather than evaluating activity done habitually. Simple observation over time confirms that - no surprise - pigs like to play. They like human contact - if you raise them in proximity to people they'll follow you around like a puppy. They like other species contact. Some farmers I know keep bowling balls in their pastures to give the pigs something to do - pigs get bored, ergo, they can get excited by their environment. None of this is in contradiction to to the paper, only to the notion that pigs get smart if you reward them with a treat. As for not eating them, that's ok - so long as you're willing to give up on actually having pigs in the world, because they will all become extinct if we don't eat them. And I feel somewhat ambivalent about that- and have no qualms about eating them, either.

    On the pets front, well, having recently acquired a dog - and a terrier at that - I can definitively say he has changed my life. He has NOT made us more relaxed, or less stressed because he's a TERRIER! He is always alert and rather on edge. He's fun, he's playful, he's charming, he's interesting, but if I wanted something to reduce stress in my life it would NOT have been this dog. I don't really see how this is different from adding any other person to your social world. I love my son, and he has enriched my life by/and making it MUCH more complicated, anxious, challenging - and fun, too. I have other friends who add their own charms to my pallid experience. Of course, their own lives mean something extremely profound in their own terms - shocker! "Pets" is far too nomothetic a category to capture the value of engaging with others.
    - Brad Weiss
  2. January 7, 2011 9:16 AM EST
    Brad, that's just it- my utopian self wants the measured-before-and-after stimulus experiment to just go away, and for people to simply flood the pigs' environment with cool stuff to do. Habitually! As for Herzog & pets, right, ask any parent (or anyone who cares for lots and lots of cats), more stress can sometimes correlate with more fun. Herzog wasn't only asking about a link between "pet ownership" and lower levels of stress, but also between pets and a whole series of physical and mental health measures. The methodologies pushed in both pieces pieces of writing are just too simplistically reductive for me. Which, I guess, is why I'm a fan of qualitative case study work... which isn't so typical in animal behavior/primatology.
    - Barbara J. King
  3. January 7, 2011 9:18 AM EST
    I agree Barbara with your reservations about the Aniaml Behaviour article (which I have NOT read but will) and the Herzog Op Ed (which I HAVE read). Are we sure we are measuring the right parameters?
    - Sian Evans
  4. January 7, 2011 9:44 AM EST
    I guess I liked Herzog's piece because it disturbs me that the pet food and other industries use the studies that support a positive health impact for human pet owners to promote pet ownership. Although I am totally with you Barbara (and Brad)that there are all sorts of wonderful reasons for people to live with companion animals, there is a lot of irresponsible pet ownership out there.

    I also don't have a problem eating pigs, but I do have a problem with factory farming and the conditions in which most farm animals are raised. I think farmers who raise pigs humanely (with access to pasture and companionship) would find the Animal Behavior study at least a little silly. Anyway, thanks Barbara, this is very interesting!!
    - Molly
  5. January 7, 2011 9:55 AM EST
    Brad, would pigs really become extinct if they weren't people food? and I agree with both of you that animal companions can bring stress (and also tremendous grief)--on the other hand, the stress of working with my dog when he was a pup was a whole different kind of stress than that of working with people, and on the whole, the endeavor was much more immediately satisfying (and the satisfaction lasts for years!) Happy New Year--Barbara, I'm glad the blog is back!
    - Colleen
  6. January 7, 2011 10:28 AM EST
    Sian, I'll be interested in your thoughts on the AB article. Molly, that's a point I'd not thought of- yes, the pet industries do push 'enhanced benefits for living' in terms of pet ownership, obviously for their own financial gain. Have you read Herzog's book? I've not, yet. And Colleen, it's an equally interesting point, that the quality of stress differs working with (many) animals versus (many) people. This rings true for me as well.
    - Barbara J. King
  7. January 7, 2011 3:13 PM EST
    Hi Colleen. My understanding is that almost all populations of feral pigs are only able to reproduce because of their proximity to domesticated pigs - pigs in the wild are the joint product of "escapees" that add to the genetic stock. And given the fact that pigs were one of the first domesticated animals- maybe even prior to dogs, according to some (no, Barbara?) it makes sense that "wild" pigs are more like hybrids with ever-present access to farmed ones. There'd be warthogs, I guess, and perhaps feral pigs would adapt to end up like wild dogs. Can't cite the sources, but I've certainly read this claim often.

    And, yes, different "stresses" and "benefits" from different companions- that's part of my point. Such methodologies rarely capture social experience, of any species, that is likely to be irregular and idiosyncratic, and so not comprable i in the quest for a uniform metric of utility.
    - Brad Weiss
  8. January 19, 2011 5:39 PM EST
    What a great blog, thanks Barbara.
    As a conservation biologist who began my academic life as an ethologist working (quite regrettably) in a medical research lab, I am now constantly amazed and dismayed by the amount of funding and tenure-advancing time that goes into ridiculous studies like the pig research you cite.
    Let's just call a spade a spade and address the huge sentient, intelligent, emotional, able-to-feel-love-and-pain elephant in the living room: we don't need one more study that tells us what our instincts, or if you prefer, intuition, or better yet, common sense tell us. (And if common sense isn't good enough, how about acknowledging the collective knowledge of family farmers over the centuries, if we are talking livestock.) We just don't need any more such studies to waste precious funding on, and who in tarnation continues to fund such hooey, no questions asked? I call it hooey not for its lack of rigorousness, but that's just the problem. If a scientific experiment is incredibly silly, cruel, and/or pointless, but it still diligently pursues objectivity, rigorousness, and the rules of adequate experimental design and statistical analysis, does this mean it is acceptable, and indeed should be funded and applauded, published, especially if said study ridiculously purports to advance our knowledge on an applied topic or concept? Where is that debate among scientists?
    If such a debate sounds subjective, it certainly should, since we as humans are subjective creatures living in a subjective world of obvious preferences and judgment when it comes to what is determined to be valuable.
    However, we are still capable of determining that testing on humans against their will to be unethical, and it is not allowed, and obviously not funded. Can we not - in the scientific world of our judgmental peers - begin having a dialogue about what studies are more or less valuable, as well as ethical (and I don't believe the definitions of these terms are mutually exclusive). The ethical debate should not be raging only between animal welfare groups and laboratories or other capitalist ventures, it should be between scientists, and it should include serious debate over the value of entire groups of experimentation. Isn't it time we started calling out the plethora of research that is really telling us something we already obviously, painfully know, even if it hasn't been assigned a statistical p value via experimentation, especially when such research subjects other sentient beings to hardship at the very least?
    I know how to make my dog happier, and thus my life less stressful (and happier too), through a connection I have made with my dog, through developing a cognitive awareness very much bound up in love. I have used some cues from my knowledge of canine behavior, but mostly, I use intuition, and love. I have not conducted one single controlled experiment on him, I have no statistics to support my conclusions on how to make my dog happier. But I have results, based on what I feel, and what I observe him to feel. I daresay that no one need develop a study to show what I feel is real, or provides a positive physiological stimulus to my brain, heart, etc. But if you aren't sure if my dog is truly happier, you will have to ask my dog.
    - Renee Owens

Selected Works

Why are animals so irresistible to us? Why do we live with and care so deeply about them? From the famous "art caves" of ice-age Europe, to the ancient villages where animals were first domesticated, to stories of apes, whales, dogs, and cats doing fascinating things today, King weaves together a scenario about the animal-human bond that encompasses our past, present and future.
Can scientists discover a prehistory of religion just as they have traced the evolution of technology, language, and art? What does compassion in chimpanzees, or burial patterns in our human ancestors and Neanderthals, tell us about the origins of religion? In Evolving God, named a Top Ten Religion Book for 2007 by the American Library Association, Barbara King explores these questions.
How do chimpanzees, bonobos, and gorillas-- the African apes -- communicate using body postures and gestures? Using her many years of experience studying these apes, Barbara King answers this question in a book that offers a new perspective on the evolution of language.