Science and Medicine: Human Behavior

Washington Post staff writer Shankar Vedantam, who writes the weekly Department of Human Behavior column, was online Monday, March 19 at Noon ET to discuss today's science page article about birds who behave like mobsters -- and what such behavior may reveal about the evolutionary roots of human behavior.

He was joined by Jeff Hoover, an avian ecologist from the Illinois Natural History Survey.

Read the story: Behavior May Suggest We're Not Only Human (Post, March 19)

The transcript follows.

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Shankar Vedantam: Thanks so much for joining us for this online chat today. We will be discussing my science page story about whether human behavior has very ancient evolutionary roots. I am so pleased that we are being joined today by Jeffrey Hoover, an avian ecologist at the Illinois Natural History Survey in Champaign, who just completed a decade-long study of cowbirds that explains how they sometimes behave like mafia gangsters.

I am also happy to take any questions related to my Department of Human Behavior Column -- today's piece was about what insights Shakespeare and King Lear may have to offer the Bush Administration. The column, as many of you know, explores what news events reveal about human behavior.

Jeff and I will answer questions on the human/bird behavior story for the first portion of the chat and then I will respond to comments, questions and feedback on the column.

Buckle up!

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Shankar Vedantam: Jeff:

Do you think we could start by having you tell us why you decided to study cowbirds -- and whether the mafia behavior you found surprised you?

Shankar

Jeff Hoover: I had been studying the interactions between cowbirds and this particular host, the Prothonotary Warbler, for a decade. During that time we had never removed cowbird eggs, because we wanted to see what the consequences of raising cowbirds was for the warbler. Then, in a separate study, we started to remove cowbird eggs to maximize the production of warbler offspring.

When we did this, we discovered that by removing the cowbird eggs, we were somehow increasing the failure rate of the warbler nests. The only way we could think of to explain it was that the cowbird adults were playing a role.

That led us to do an experiment whereby we removed cowbird eggs from some nests and not others, and also controlled cowbird access to nests.

We found that when we left cowbird eggs in nests or did not allow cowbirds access to nests, these nests were "safe". When we removed cowbird eggs and allowed cowbirds continued access, we had an unusually high failure rate. We were able to implicate cowbirds in this way.

This result stunned us because it showed us that the parasitic and predatory behaviors of these cowbirds were much more sophisticated than we had originally thought.

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Savage, Md.: Is the theme of your story really news? After all, Charles Darwin wrote "The Expression of the Emotions in Man and Animals" way back in 1872, and Lorenz and Tinbergen received Nobel Prizes for their work in ethology in 1973.

Shankar Vedantam: Thanks for your question. I am honored that you would compare my work with Darwin! And I have no problem whatever acknowledging that Darwin did indeed weigh in on this issue in several of his books, including The Descent of Man. That said, what prompted us to revisit the issue were two fascinating new studies -- the one by Jeff Hoover and another study by Emily DuVal who found that male lance-tailed manakins play wingbird for each other; beta males help alpha males find mates.

I should also note that even though Darwin's ideas are more than 150 years old, many (most?) people continue to believe that humans are innately different (and superior) to other species. Studies like Hoover's and DuVal's seem to be a good reminder that our superiority complex is unfounded.

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Bethesda: Why is it required for male birds with all that beautiful plumage color; i.e. the brilliant, red cardinal to sing so loud and persistently to get attention? I think I've seen them pursuing the female, also. This seems unnecessary waste of energy. What's going on? Marcus

Jeff Hoover: Bright coloration and strong singing in male birds is a signal to females of the quality of the male. Many studies have shown that females prefer certain traits in males that are associated with producing the best offspring possible. We call these traits sexually selected. Ornamentation, bright colors, and bold or enthusiastic song in male birds are all examples of this. It works if the male with the brightest coloration or most vigorous song is preferred by females and therefore gets to mate with more females and produce more offspring than a less bright male with a poorer song. If the females, by mating with such a male, produces high-quality offspring, the preference in females for bright and vocal males is perpetuated.

Also for this to work, being a bright male who sings a lot has to be an honest signal - it has to be associated with the quality of that male.

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Louisville, Ky.: Do birds or other animals use any natural occurring chemical that alters their normal brain function?

Jeff Hoover: One example that I can think of is Cat nip. I am not sure of the specific way it alters brain function, but I know from observing cats that they are attracted to it and it really changes their behavior.

A less obvious example may be Cedar Waxwings eating overly ripe fruit in the spring. The fruit is fermented enough that if the birds eat enough of it they get "drunk". I think that the birds are eating the fruit for nutrition and the "drunkenness" is an unexpected consequence.

Shankar Vedantam: Right, Jeff. That is exactly how I feel about many fermented beverages myself.

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Laurel, Md.: I have been following Frans de Waal's work for more than 15 years, and ten years ago I got to meet him at the National Zoo's Great Ape House. I highly recommend his books "Chimpanzee Politics" and "Peacemaking Among Primates" (the primates surveyed in the latter are chimpanzees, bonobos, two species of macaques, and humans).

Jeff Hoover: Yes, I have heard that these books are a good read. Very insightful.

Shankar Vedantam: I agree with Jeff.

I found Frans de Waal to be a terrific source, full of wise and witty insights, and a ready ability to connect his research with everyday life -- a quality that is in somewhat short supply in the world of science!

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Silver Spring: Is there any evidence of "mood disorders" among other species?

Shankar Vedantam: I think scientists are always on the lookout for animal models of human disorders, and psychiatric disorders are no exception. That said, I think it is probably more difficult to find an animal model for a mood disorder than it is to find an animal model for, say, cancer, because none of us can get inside the heads of animals to know whether they experience moods in the same way humans experience moods.

In fact, I suspect this is especially difficult in mental disorders that are mood related, because so much of the experience of an affective disorder involves subjective perception.

If anyone else knows better, do post a note and I would be delighted to be set right.

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Shankar Vedantam: Another question, Jeff. When you see such complex behavior in other species, does it make you wonder about the evolutionary roots of complex human behavior?

Do you think the mafia cowbirds are actually thinking about what they do in the way a Tony Soprano might?

Shankar

Jeff Hoover: This is a great question. I think that are examples of analogous or similar behaviors in other animals for behaviors that we often think of as solely human. Tool use is an example. We thought only humans, but we now know that chimps as well as birds also use tools.

It is likely that we, as humans, have a better ability to assess the consequences of our actions - to be reflective or premeditated. The cowbirds, for example, may be behaving in a fairly pre-determined way, a way that helps to maximize their own reproductive output. I do not think that the female cowbirds fly out to forage in nearby pastures and scheme with the other cowbirds gathered there.

Jeff Hoover: I think that one thing in common with many of these behaviors common among many different animal species (including humans) is that the behaviors serve to further the cause of the particular individual using them.

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Shankar Vedantam: During our interview, Jeff, you also mentioned that there may be some evidence that cowbirds also "farm" nests. Space restrictions did not allow me to get into this -- do you think you could tell readers a little about this very interesting (or, depending on your perspective, very disturbing) practice?

Jeff Hoover: Sure, I would be happy to.

This also adds to the sophistication of the cowbirds behavior.

As mentioned in the article, cowbirds have a narrow window of time to get their egg into the nest of a host. Sometimes cowbird females find nests that are too far along to be effectively parasitized. By damaging the contents of those nests (be they eggs or nestlings of the host) the cowbird can cause the host to most a slight distance and build a new nest that will provide a new opportunity for the cowbird. The cowbird can then plant an egg in this new nesting attempt.

What we found is that some of the non-parasitized warbler nests also failed at a rate higher than expected. The renesting attempts of the host warblers following the failure of their nests nests (failure because of mafia and farming behavior)were subsequently parasitized at a very high rate (85% of the time). This suggests that the female cowbirds are good at getting their eggs into the renests of the warbler hosts after causing the initial attempt of the host to fail.

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Takoma Park, Md.: Hi Jeff, -- Shankar premeditated my question! You said "I do not think that the female cowbirds fly out to forage in nearby pastures and scheme with the other cowbirds gathered there." Does any particular evidence give you grounds to think they don't? Thanks again for this discussion. It's great.

Jeff Hoover: The cowbirds certainly interact with each other away from where they lay their eggs (nearby foraging habitat), so I would not rule anything out at this point. Just my speculation.

We almost always see the female cowbirds visiting nests by themselves. Occasionally we see two females arrive together and we are trying to work out if there is the possibility that some female coalitions exist (mother-daughter; sister-sister). What we hope to do is to determine whose (cowbird) eggs are put into particular nests and if multiple females are responsible, are they related or do they spend time together than with other females away from the places where they are parasitizing nests.

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Takoma Park, Md.: Hi Shankar and Jeff. Very interesting topic. What do you think about Konrad Lorenz's idea (King Solomon's Ring) that birds and fish who act like humans act when humans are in love, are feeling the same love feelings?

As I understood K.L.'s idea, it was based on an argument by parsimony. That is, why start from an unjustified assumption -- that romantic love is for some reason a uniquely human experience -- to imagine some baroque construct to account for love-like behavior?

It reminds me of my college humanities classes where the grad student in charge told us that romantic love didn't exist before the Age of Chivalry, because there wasn't any proof that it did. Give me a break... that's bad logic.

Shankar Vedantam: I think this raises a raft of interesting questions. When we think of human behavior we immediately ascribe agency to it, which is not something we routinely do with animal behavior. There is a pigeon outside my home that has currently been sitting on a couple of eggs for the last three days, and I have been wondering about whether she knows what she is doing, or whether she is just doing it "instinctively."

Of course, that is such a messy word and often just a euphemism to say that a creature is not thinking about it the way a human would. In my article today, Frans de Waal argued, I think persuasively, that the reverse of this argument may also be true. While it is possible that other animals may be "thinking" the way we do, it is also possible that many of our thinking behaviors are indeed automatic or instinctive. They don't feel that way of course, but at least one popular vein of research in neuroscience would suggest that the feeling of agency we have over our thoughts is something that the brain layers over processes that are actually largely automatic. (I wrote an article a while ago about Harvard researcher Daniel Wegner's book, The Illusion of Conscious Will, which explores some of these questions.)

A lot of this of course is really dancing around the C word -- what does it mean to be conscious. Are other people's experience of consciousness the same as our own? What about other animals' experience of consciousness? I have many more questions than answers!

Jeff Hoover: I could not improve upon Shankar's answer.

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Burke: Since chimps are 98+ percent genetically identical to us, wouldn't it be more surprising for them NOT to show thoughtful social behavior that resembles ours?

Jeff Hoover: I agree....

Shankar Vedantam: Yes, this is certainly makes common sense. That said, the devil's advocate in me suggests that small differences in genotypes can produce what seem like large differences at the level of phenotypes.

But if we were to step back, the most parsimonious argument is certainly that species that are closely related in terms of genes ought indeed be similar to each other when it comes to behavior ...

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Just curious: What does an avian ecologist do that an ornithologist doesn't?

Jeff Hoover: It is just a label. Avian ecologists and ornithologists typically have similar interests.

I use avian ecologist to describe myself because I am interested in birds and their interactions with the natural world (not to say that someone calling themselves an ornithologist is not also similarly interested). In the past I have heard the comment "Oh, you are an ornithologist, so you are only interested in birds" and for whatever reason, I do not get that comment when I call myself an avian ecologist.

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Bethesda, Md.: Is it easy to break animal behaviors down by gender? I think there might be general trends, but then times when animals behave contrary to how people think they should in terms of how genders should act. Much like people I don't think there can be any definitive statements on behavior based on gender for the most part. What evidence have you seen though?

Jeff Hoover: You make a good point.

I think that often the behaviors may differ by sex, often based on the different roles the sexes may play in promoting their own fitness (survival, growth, and reproduction). But even though the behavior may be different between the sexes, they tend to still follow the same pattern of maximizing the benefit to the individual displaying the behavior.

Shankar Vedantam: I personally find arguments that seek to explain human gender relationships in terms of the gender relationships of other animals absolutely infuriating. Even a cursory understanding of evolution would show that there is no prototypical male or female behavior. Species do what they need to do, and the special dictates of evolutionary niches cause males and females in various species to adopt very different strategies.

Here is a wonderful excerpt from Charles Darwin's The Origin of Species that speaks to how we ought to think about different kinds of male and female behavior: "It may be difficult, but we ought to admire the savage instinctive hatred of the queen-bee, which urges her instantly to destroy the young queens her daughters as soon as born, or to perish herself in the combat; for undoubtedly this is for the good of the community; and maternal love or maternal hatred, though the latter fortunately is most rare, is all the same to the inexorable principle of natural selection."

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Kensington, Md.: I am not awestruck but such studies, but I am biased, perhaps warped, by being an economist. Behavior seems to be about optimization, and it does not surprise me that similar patterns of behavior are repeated within the animal behavior, even among humans. There must be some efficiency or benefit to these behaviors that have made the species who utilize them exceed. As to whether humans have learned these from social interaction or have inherited these things via evolution, well that is not something this research comes anywhere near answering.

I guess I see humanity in all the inefficient behavior we engage in--rituals (not tied to mating), obsessions, etc. Behavioral studies of rationality often work better with animals than they do with humans.

Shankar Vedantam: Thanks for the comment, Kensington. If I were to wager a bet, I would say that animal behavior probably just as much "irrationality" to it as human behavior ... indeed, irrationality may only be the term we use because our metrics are limited. We see (to pick a random example) people who stash their money under their beds and therefore lose value to inflation as being "irrational" in economic terms, but their behavior is also rational in that it is prompted by their fears and sense of risk. Only in a closed system, where we limit outcomes to what we can measure (in this case, maximising money) can we describe this as irrational behavior. With animal studies we necessarily have to limit ourselves to what we can measure, since we have no understanding of the subjective nature of what it is to be a cowbird. So it is not surprising that we would find more rationality in such studies.

Thoughts? Comments?

(Also, if anyone does have a subjective understanding of what it is to be a cowbird, please write immediately!)

Jeff Hoover: The cowbirds, by using the many behaviors in their repertoire, are working to maximize their reproductive output.

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South Carolina: I thought this was an interesting article that brought up a lot of important points about humans and our place in nature and evolution. The article did leave me with two questions: first, is it really so surprising to think that along with physiology our behavior is also a product of evolution? I mean, why wouldn't it be? Our need for companionship, desire for successful mates, protection of children, and other such behaviors are all exhibited in the wild, why wouldn't our instincts have an evolutionary source just like other animals?

Secondly, while I agree with the premise of this article, I wonder how much anthropomorphizing is occurring in finding human-like behaviors in other animals. In the case of the cowbirds, shouldn't we be saying humans (the mafia) are behaving more like the cowbirds than the other way around? It seems to imply intent on the bird's part if we say they are acting like mobsters, and could open the door for other anthropomorphic comparisons which have no basis in science, but instead imprint human feeling and emotions onto an animal. For example, using the term "gay" to describe animals that attempt to mate with others of the same sex. This is a purely human term to describe humans who are sexually attracted to others of the same sex, and can not be used to describe animals who do not have the same sexuality spectrum as humans. Motivations in the animal world are not always the same as in humans.

Shankar Vedantam: Thanks for the excellent questions and comments, South Carolina. I agree with most of what you say. Jeff has been especially cautious to avoid anthropomorphizing cowbird behavior and I tried to do be careful about it too -- indeed, that was why I situated the bird studies in the larger context of how human behavior evolved from other species. So yes, I absolutely agree that it makes more logical (and chronological!) sense to say that human behavior derived from ancestral influences such as the cowbird rather than to say cowbirds are behaving like us.

All that said, I think there is far more controversy out there in the popular imagination about how much human behavior derives from the behavior of our evolutionary predecessors -- certainly far more controversy than we have seen today in this science forum.

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Durham, N.C.: The question is not whether animals exhibit behavior--what else would they do. It is whether it is calculated or has become neuronally hardwired. The cowbird behavior is certainly unexpected, but In any situation, there is likely to be only a few "useful" behaviors that might be exhibited. So perhaps a question would be whether cowbird terrorism is unique or is also used by other bird species that use "nannies" to raise their young?

Jeff Hoover: Evidence for this mafia-like behavior has also been found in a study of parasitic cuckoos (the Great spotted Cuckoo) and its host (the Magpie) in Spain.

Two other study systems have documented some evidence for farming in brown-headed cowbirds with two additional hosts: song sparrows in Canada, and Red-winged Blackbirds in Wisconsin.

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Washington, D.C.: At the end of the news article, it is stated that the mafiosi might claim evolution as a defense, but that this would not work because he or she is aware of the behavior they choose. Why is it wrong for the strong to bully and coerce the weak if it is as natural as the birds and the bees?

Jeff Hoover: I guess that the way in which human society has evolved has made it so that in most/many societies bullying and coercion are deemed to be inappropriate behavior. This seems to not be the case among brown-headed cowbirds.

Shankar Vedantam: Right. Human ideas about right and wrong involve elements of social construction, which is why you see that different societies in different eras (or different cultures today) often enshrine different models of right and wrong. I think people fear that it will weaken the moral code to say something like this, but I am not sure why it would. Understanding the motivations behind our actions does not necessarily change how we feel about our behaviors.

Knowing that evolution has predisposed me to love my daughter, for example, does not make me love her any less.

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San Jose, Calif.: One of the things you wrote here, was that the behavior favored the individual. Isn't it better to say that the behavior favored the gene(s) that caused the behavior? Here I'm thinking of the reasoning popularized by Richard Dawkins. Do you agree that, from an evolutionary perspective, it is better to think of the animal as a vessel for the genes?

Jeff Hoover: Yes, I agree.

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Rockville, Md.: In your experience Dr Hoover, have you ever come across a non-parasitized warbler that has "paid" protection against cowbird aggression?

Jeff Hoover: I am not sure what you mean by paying protection. In our example, the warblers "pay for protection" by accepting the cowbird egg in their nest. The cowbirds do not necessarily protect the nest from other animals that might eat the eggs or nestlings (raccoons, snakes, etc), but by accepting the cowbird egg, the warblers have a better chance of producing some of their own offspring than if they were to eject the cowbird egg and suffer the consequences (female cowbird returning and damaging or removing the hosts eggs).

The warblers presently accept cowbird eggs and this is one possible explanation for why they do.

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Jeff Hoover: Thanks to all who participated. Great questions and observations!

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Re the Bard: Enjoyed the article today. Perhaps because it reflects things I've believed for some time. As the article states, this falls into the category of me liking what is affirming of me. There in lies the problem. If its natural to like being liked, how do we learn or train ourselves to accept a more accurate view rather than the one that is simpler and easier to accept due to it's flattery? As the Dutch quote states it's very hard to find powerful men or beautiful women or these days powerful women or beautiful men with accurate views of themselves.

Still one wouldn't necessarily suggest masochism? After all, it would be easy to open one's self up to criticism just for the sake of criticism and allow to great a voice to that which may not be objective.

Shankar Vedantam: I think you raise a lot of excellent points. (And I also agree that the gender dynamics of that Dutch proverb are dated!)

As with many of the psychological studies I write about for the Monday column, I don't think psychology in the end can tell you what is right and what is wrong. It is true that we all need outside voices and criticism to be fully aware of our blind spots (a la King Lear) but it is also true that endlessly seeking evidence can also be an excuse for inaction (a la Hamlet.)

There are no simple, black and white rules for effective human behavior. And sometimes important rules contradict one another, so the wise not only know all the rules, but also know which ones to break -- and when.

That's all the questions we have time for today. Thanks to everyone for weighing in -- and a special thanks to Jeff Hoover for sparing an hour to field some questions.

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