Zeroing In On Parrot Math Abilities

It may seem surprising, but the concept of “zero” is actually a relatively recent mathematical innovation. Indeed, the first rudimentary use of a zero-like notation didn’t appear until around 300 BC, when the Babylonians began using a special placeholder symbol to designate the absence of another value in their base-sixty number system. While revolutionary in its own right, the Babylonian null placeholder was still rather limited (for example, it couldn’t be used alone and never appeared at the end of a number), and another millennium passed before gifted Indian mathematicians and astronomers introduced a fully functional “true zero” as part of a formalized system of arithmetic operations. Some 1,500 years later, with this important mathematical foundation finally in place, Apple launched the iPhone on the AT&T wireless network.

Are there any parallels in the animal world, any similarly gifted nonhuman mathematicians that have innovated with the concept of zero?

The answer seems to be yes: Alex, the male African Grey Parrot of book and movie fame (Alex & Me), may go down in history as the parrot equivalent of Albert Einstein, revolutionizing parrot mathematics with his insight into concepts of nothingness.

How many crackers do I see? None! (image: The Alex Foundation)

It was in late 2003, early 2004 that Alex appears to have had his great breakthrough regarding the mathematical usefulness of zero-like concepts. At that time, Irene Pepperberg and Jesse Gordon of Brandeis University, who had been working with Alex over an extended period on a variety of cognitive and communicative studies, decided to conduct some experiments to explore the extent of his numerical competence.

Alex already was adept at tests requiring him to identify numbers of objects – he knew the English words for one through six, and could provide accurate verbal responses to questions about, for instance, how many green blocks were included in a mixed array of blue, red and green blocks and balls. Pepperberg and Gordon now wanted to see whether Alex really understood the numbers he was providing and could grasp the interchangeability of numerical questions.

To do so, they flipped things around: rather than asking Alex to provide the number of objects in particular groupings as he had in prior experiments, they went in the other direction by asking him to indicate which object groups were associated with a particular number. That is, they presented Alex with a tray of objects of various materials, colors and shapes (for example, six green plastic spoons, four yellow tops and three orange wooden sticks), and asked him questions such as “What color six?” and “What toy four?” Alex’s task was to look at the objects on the tray and then respond correctly (in this case, with “green” based on the six green spoons and “top” based on the four yellow tops).

(I know, this all sounds a bit like Jeopardy: “Please be sure to phrase your answer in the form of a question…”)

Perhaps not surprisingly, Alex aced the test, responding correctly to this new battery of questions over 80% of the time. More significant, though, is how Alex – apparently bored with the questioning – spontaneously extended the scope of the experiment:

On the 10th trial within the first dozen, Alex was asked “What color 3?” to a set of two, three, and six objects. He replied “five”; the questioner asked him twice more and each time he replied “five.” The questioner, not attending to the tray, finally said “OK, Alex, tell me, what color 5?” Alex immediately responded “none.”

Now, Alex had previously been trained to use the word “none” in a different context – comparing objects for similarity or difference (for example, to respond to a question about which of two identically-sized objects was bigger) – but he had never been taught to use “none” to describe a quantity that was not present. Fascinated, Pepperberg and Gordon randomly interspersed six more “none trials” into the ongoing experiment. It turned out that Alex’s response was no fluke – he gave the correct “none” response in five out of six of these trials, an accuracy rate of 83.3%.

Here’s a brief video in which Pepperberg describes the experiment and Alex’s unexpected use of the “none” concept:

Thus, it appears that Alex spontaneously used “none” in a zero-like manner to label a null set and designate an absence of objects. As the researchers summarized it, “the notion of none, even if already associated with absence of similarity and difference (and lack of size difference), is abstract and relies on violation of an expectation of presence; that Alex transferred the notion from other domains to quantity, without training or prompting by humans, was unexpected.”

While Alex’s use of “none” may not be as full and robust as the true zero concept that we use today, it nonetheless (no pun intended) is quite impressive. Moreover, Alex’s insight may prove to be quite practical, with the parrot concept of “none” providing helpful guidance as we attempt to answer some of the more pressing questions of our time, including:

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ResearchBlogging.orgPepperberg, I., & Gordon, J. (2005). Number Comprehension by a Grey Parrot (Psittacus erithacus), Including a Zero-Like Concept. Journal of Comparative Psychology, 119 (2), 197-209 DOI: 10.1037/0735-7036.119.2.197.

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It’s Not That Funny, the Chimp Is Just Being Polite

“Ha ha ha,” politely hoots the chimpanzee, not exactly rolling on the floor. He’s not laughing spontaneously or for very long, but he does want to encourage his playmate to keep up the antics.

Continuing on in the spirit of last week’s post on the rodenty laughter of tickled rats, today’s post features a recent study on social laughing in chimpanzees.

As we all know quite well from experience, human laughter is a many-faceted thing. Sure, we sometimes laugh spontaneously and joyously (this is known as Duchenne laughter), but we also use our laughter as a multipurpose social tool, enabling us to establish rapport with social partners, to announce that we are nonthreatening and open to further communication, to alleviate tension and break barriers when meeting an unfamiliar face, and even to exclude others by demonstrating scorn or derision. In short, laughter sends a wide range of communicative signals, and our mastery over its many varieties lies close to the core of what’s sometimes referred to as emotional intelligence – the sophisticated way in which we assess, understand and navigate social situations.

Well, do any other animals manage their laughter for social reasons, or is nonhuman laughter inevitably spontaneous and reactive, like the high-pitched chirping of tickled rats? (Not that this would be a bad thing, just ask the rats….)

Marina Davila-Ross and her co-researchers from the University of Portsmouth decided to test some chimpanzees to find out. They studied 59 male and female chimpanzees of all ages living in four separate colonies at the Chimfunshi sanctuary in Zambia – two smaller colonies that had formed within the past five years, and two larger ones that had been together at least 14 years. In general, the chimps in the colonies that had been together longer belonged to more established families and had grown up with more opportunities to play with others in a familiar social environment.

Did you see the look on Mr. Mookimbo’s face when he bit into the “cake”? (photo credit: David Eppstein)

First, the researchers videotaped almost 500 one-on-one play sessions, documenting what the chimps did and when they laughed. The researchers recorded spontaneous laughter as well as laugh replications (laughter that followed within five seconds after a playmate’s laughter), and further noted whether the laugh replications occurred during the first second (rapid laugh replication) or within the next four seconds (delayed laugh replication).

The research team soon discovered that the chimps’ spontaneous laughter was substantially different than their laugh replications: the laugh replications were much shorter, consisting of significantly fewer calls per laugh series. Among other things, the researchers also found that:

  • Chimps in the more recently-formed colonies replicated the laughter of their playmates more frequently than did the chimps in longer-established colonies, even though the aggregate amount of all laughter in each of the colonies was relatively comparable.
  • Infants generally engaged only in spontaneous laughter, with little or no laugh replication.
  • Play bouts lasted significantly longer when they were accompanied by laugh replications than when they weren’t.
  • Laugh replications peaked at two discrete points, first at about .7 to .8 seconds after the initial laugh, and then again between 2 and 3 seconds after the initial laugh.

Next, the researchers tried to verify whether laugh replications were specifically triggered by a playmate’s laughter, and not just coincidentally associated with it. They combed through their previously-recorded video footage and, for specific chimps and their playmates, found matching play scenes that generally lined up very closely in terms of specific behaviors (chasing, tickling, grabbing, wrestling, gnawing, hitting, jumping, game playing, etc.), but that differed in one important respect – in one scene, the chimp’s playmate engaged in a potentially-triggering bout of laughter; in the other scene, it did not. When the researchers reviewed these paired scenes, they found that a chimp was significantly more likely to laugh in those scenes in which the other chimp laughed first, suggesting strongly that replicated laughter really was triggered by the playmate’s laughter as opposed to any other aspect of the chimps’ play behavior.

Well, one thing’s for sure, they’re not going to trust us with *next year’s* holiday decorations… (photo credit: Christa Saayman)

Based on their findings, the researchers concluded that chimps laugh in response to the laughter of their playmates, that this laughter differs in acoustic form and timing from their spontaneous laughter, and that the purpose of their non-spontaneous laughter appears to be to prolong social play, promoting group cohesion and perhaps providing the chimps with important social advantages.

In support of these conclusions, the researchers also observed that the lack of laughter replication in infant chimps suggests that socially managed laughter is a skill that chimps learn as they mature. Further, they hypothesized that the chimps in the newer colonies may have engaged in more replicated social laughter because they were living in a less predictable social environment and may have had a greater need to manage laughter in order to establish social cohesion.

So, next time you’re at a party with a group of laughing chimpanzees (don’t think I don’t know you, AnimalWise readers), listen very closely to the rising levels of laughter around you. While you might be tempted to believe that you’re hanging out with a particularly hilarious crowd, the truth may be that your fellow party goers are simply adept at using laughter as a social lubricant. Let the good times roll!

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ResearchBlogging.orgDavila-Ross, M., Allcock, B., Thomas, C., & Bard, K. (2011). Aping expressions? Chimpanzees produce distinct laugh types when responding to laughter of others. Emotion, 11 (5), 1013-1020 DOI: 10.1037/a0022594.

The Ticklish Laughter of Rats

Let’s go tickle some rats.” With those epic words, neuroscientist Jaak Panksepp and his undergraduate assistant, Jeff Burgdorf, went into their Bowling Green State University lab to engage in the hard work of science.

Panksepp, who had been studying play behavior in young human children as well as 50-kHz ultrasonic chirping noises made by juvenile rats during rough-and-tumble play, had just put two and two together: “I had the ‘insight’ (perhaps delusion) that our 50 kHz chirping response in playing rats might have some ancestral relationship to human laughter.1

The rest has been history, and today Panksepp is undoubtedly the world’s foremost authority on rodent tickling:

As they progressed with their research, Panksepp and his colleagues found that many of their rats seemed irresistibly drawn to tickling, chasing after the ticklers and making substantially more play chirps while being tickled than during any other behavior. But the researchers weren’t content with anecdotal observations, and over the course of several years and a number of experiments, they systematically documented a dozen separate lines of evidence suggesting that the rats’ tickle chirping corresponded behaviorally to playful laughter in young human children.2

No, I went "chirp, chirp, chirp." If I'd been laughing, it would have been "chirp, chirp, chirp."

They compiled data establishing, among other things, that certain areas of the body are particularly ticklish (the nape of the neck, for you do-it-yourselfers), that the most playful rats tend to be the most ticklish, that rats can become conditioned to chirp simply in anticipation of being tickled, that tickle response rates decline after adolescence, that young rats preferentially spend time with older ones who chirp more frequently, that the tickle response appears to generate social bonding, that chirping decreases in the presence of negative stimuli (such as the scent of a cat), that rats will run mazes and press levers to get tickled, etc. Based on their research and observations, Panksepp and his fellow researchers hypothesized that rats, when being tickled or engaging in other playful activities, experience social joy that they vocalize through 50 kHz chirping, a primordial form of laughter that is evolutionarily related to joyful social laughter in young human children.

Does it look like my name is Elmo?

It’s safe to say that the neuroscientific community did not exactly rush to embrace this hypothesis. Behavioral neuroscience can be a particularly conservative and skeptical field, one that has traditionally been extremely wary of any theorizing about emotions controlling neural processes or behavior in animals. Since subjective experiences cannot, after all, be measured directly, it has been considered far more appropriate to those functional brain activities and processes that can be scanned and measured objectively, and to simply deny or ignore the possibility that animals experience complex emotional states such as joy, at least in the context of scientific research. As Panksepp put it:

Of course, it was hard to publish this kind of work, and it was ironic that the publication of our initial manuscript was impeded by prominent emotion researchers, some of whom take pains to deny that we can ever know whether animals have any emotional feelings.3

Hahaha, we've had our little fun now, haven't we? If you tickle me again, I'll pee in your coffee.

Fortunately, time and scientific progress have been on Panksepp’s side. We have identified an increasing number of common underlying structures and processes (homologies) in the brains of humans and other mammals and, as brain scanning technologies have become more sophisticated, we have gained greater insight into neural activities triggered in connection with particular emotional experiences. While the ability to cognitively “get a joke” may depend on our incredibly advanced human neocortex, we now believe that much of the foundational brain circuitry relating to laughter, mirth, social joy, social play and emotional processing lies deep within subcortical regions, where our brains are much more similar to those of other animals.

At this point, Panksepp and his colleagues recognize that they have not definitively proven their hypothesis, but their view is essentially that they have made a reasonable case that fits their data and that hasn’t been disproved:

Until someone can offer us some data that falsifies our hypothesis, we believe our theoretical approach better reveals the true nature of the underlying processes than any intellectual scheme that simply constrains itself simply to the accurate description of the environmental and neural control of behavioral acts.4

Even acknowledging the understandable caution of neuroscientists and the obvious difficulty in drawing scientific conclusions about the subjective experiences of animals, it does seem entirely plausible (and not overly surprising) that social animals such as rats would enjoy playful romping and tickling, and that they might vocalize their pleasure in a way that was somewhat akin to basic human laughter. In fact, we hope and fully expect that, as our knowledge of comparative brain structure and function grows over time, we will see more and more studies that show clear linkages between the minds and brains of humans and other animals.

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ResearchBlogging.org1Panksepp, J. (2007). Neuroevolutionary sources of laughter and social joy: Modeling primal human laughter in laboratory rats Behavioural Brain Research, 182 (2), 231-244 DOI: 10.1016/j.bbr.2007.02.015.

2Panksepp, J., & Burgdorf, J. (2003) “Laughing” rats and the evolutionary antecedents of human joy?. Physiology & Behavior, 79(3), 533-547. DOI: Panksepp, J., & Burgdorf, J. (2003). “Laughing” rats and the evolutionary antecedents of human joy? Physiology & Behavior, 79 (3), 533-547 DOI: 10.1016/S0031-9384(03)00159-8.

3Panksepp & Burgdorf (2003).

4Panksepp (2007).

A Yawning Divide? Contagious Yawning and Empathy in Animals

A group of red-footed tortoises ran away (rather slowly) with the 2011 Ig Nobel Prize in physiology1, bringing to center stage the potential link between contagious yawning and empathy in animals. While the Ig Nobels are a tongue-in-cheek spoof of the Nobel Prizes, their purpose is not frivolous – they “honor achievements that first make people laugh, and then make them think. The prizes are intended to celebrate the unusual, honor the imaginative — and spur people’s interest in science, medicine, and technology.” Here’s the story of the tortoises’ claim to fame and what we know about contagious yawning in animals.

Tortoise yawning? I don’t think so!

It turns out that the underlying cause of contagious yawning has been something of a puzzle – why is it that when you see someone else yawn (or even hear a yawn or just think about yawning), you sometimes are overcome with the urge to yawn yourself? The most common hypotheses are that contagious yawning results either from empathy or from non-conscious social mimicry, the tendency to adopt a social partner’s postures, gestures and mannerisms. An alternative hypothesis, however, is that it may simply reflect a fixed action pattern, an innate or instinctual response to a stimulus (a triggering yawn).

No, really, go on - I'm listening... (photo: Peter Baumber)

And that’s where the red-footed tortoises lumber into the picture. Lead researcher Anna Wilkinson and her colleagues figured the tortoises would offer a good way of testing the fixed action pattern hypothesis, since they are known to yawn and respond to social stimuli, but are not believed to exhibit empathy or engage in non-conscious social mimicry.

The researchers worked very hard to induce contagious tortoise yawning, spending six months training one of them (Alexander, if you’re curious) to yawn whenever he saw a red square-shaped symbol, and then devising a series of tests to see whether six “observer” tortoises would yawn after seeing Alexander yawn. Initially, the observers were presented with three scenarios: one in which they watched Alexander giving one of his patented yawns, another in which they watched a non-yawning tortoise (Alexander?), and a third in which they simply viewed Alexander’s red square. A second experiment mirrored the first, except this time the observers watched Alexander yawn multiple times. Finally, they went to the movies, seeing clips of real tortoise yawns, fake yawns and an empty background.

And the results? Nothing, nada, zilch. The tortoises simply didn’t yawn more frequently after seeing another tortoise yawn; no contagious yawning whatsoever. This spectacular display of non-yawning in tortoises led the researchers to “suggest that contagious yawning is not simply the result of a fixed action pattern and releaser stimulus …. We suggest that contagious yawning may be controlled through social processes such as nonconscious mimicry or empathy….” Naturally, international acclaim ensued.

Apes and Monkeys and Dogs, Oh My!

So, which animals do demonstrate contagious yawning? Well, as with other cognitive realms, our views of contagious yawning have followed “AnimalWise’s Rule”: first we believed it to be an exclusively human behavior, then we observed it in chimpanzees, then we saw it in monkeys, next in dogs, now … hmm … Taste it, fur-face, I have opposable thumbs!  Ok, I lied, that’s not a real rule; I just made it up.

Here’s a run-down on what we actually know about contagious yawning in non-humans:

Chimpanzees

The phenomenon was first demonstrated in chimpanzees in 2004 when a research team led by James Anderson of the University of Stirling reported2 on a small study in which six adult female chimps watched video scenes of other chimps who were either yawning naturally or, alternatively, displaying open-mouthed facial expressions that weren’t yawns. Two of the observers (33%) yawned significantly more often in response to the yawn videos and none of them yawned more frequently in response to the open-mouth control videos, a response rate only slightly lower than that in humans watching comparable videos. In 2009, Matthew Campbell and colleagues from the Yerkes National Primate Research Center (YNPRC) expanded on these findings, reporting3 that, much like humans responding to on-screen yawns by Pixar characters, a group of 24 chimps yawned significantly more often after watching 3D computer animations of yawning chimps than after watching animations of chimps displaying non-yawn mouth movements. Finally, Matthew Campbell and Frans de Waal of the YNPRC reported4 this year on an experiment lending empirical support to the hypothesis that contagious yawning stems from empathy. Campbell and de Waal found that, consistent with studies showing that humans demonstrate greater empathy towards others they view as being similar, chimps yawned significantly more frequently in response to videos of familiar chimps yawning than they did to either videos of unfamiliar chimps yawning or videos of chimps (regardless of familiarity) who were at rest.

Monkeys

The first study supporting contagious yawning in non-ape primates was published5 in 2006 by University of Stirling researchers Annika Paukner and James Anderson, who had 22 stumptail macaques watch video clips of other macaques either yawning or making non-yawn facial movements. Although the macaques yawned significantly more in response to yawn tapes than to non-yawn tapes, the researchers noted that the macaques engaged in more self-directed scratching (a tension-relieving behavior) while watching the yawn tapes, making it difficult to differentiate between actual contagious yawning and the release of stress perhaps brought on by the yawn tapes. The case for non-hominid contagious yawning was bolstered in 2009, though, when Elisabetta Palagi of Pisa University and her colleagues published6 a study in which they recorded and reviewed over 3,200 baboon yawning displays (all occurring in the absence of stressful events or behavior). They not only found clear evidence of contagious yawning among adult baboons, but also discovered that females (but not males) tended to match the type of yawning display (baboons make different facial expressions when yawning) that had triggered their own yawn, and that the degree of contagiousness correlated with social closeness, thus supporting an empathy-basis for yawn contagion and anticipating the results of 2011 chimpanzee experiment described above.

Dogs

Lastly, in 2008 Ramiro Joly-Macheroni and colleagues from the University of London reported7 on an experimental first on multiple fronts: yawn contagion in a non-primate species and the first demonstration of possible contagious yawning across different species. In their study, 29 dogs observed an unfamiliar human either yawning or making non-yawning mouth movements, with 21 dogs yawning in response to the yawning human and not one yawning in response to the human who displayed the non-yawning control behavior.

Future Directions

I know that if the Internet were allowed to vote, researchers would spend much of their waking hours considering YouTube videos of impossibly cute kittens yawning, but I want to take this opportunity to call for a full and serious investigation into the concerning link between contagious duck wing flapping and odd French Canadian music:

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ResearchBlogging.org1Wilkinson, A., Sebanz, N., Mandl, I., & Huber, L. (2011). No evidence of contagious yawning in the red-footed tortoise Geochelone carbonaria. Current Zoology, 57(4), 477-484.

2Anderson, J., Myowa-Yamakoshi, M., & Matsuzawa, T. (2004). Contagious yawning in chimpanzees Proceedings of the Royal Society B: Biological Sciences, 271 (Suppl_6) DOI: 10.1098/rsbl.2004.0224.

3Campbell, M., Carter, J., Proctor, D., Eisenberg, M., & de Waal, F. (2009). Computer animations stimulate contagious yawning in chimpanzees Proceedings of the Royal Society B: Biological Sciences, 276 (1676), 4255-4259 DOI: 10.1098/rspb.2009.1087.

4Campbell, M., & de Waal, F. (2011). Ingroup-Outgroup Bias in Contagious Yawning by Chimpanzees Supports Link to Empathy PLoS ONE, 6 (4) DOI: 10.1371/journal.pone.0018283.

5Paukner, A., & Anderson, J. (2006). Video-induced yawning in stumptail macaques (Macaca arctoides) Biology Letters, 2 (1), 36-38 DOI: 10.1098/rsbl.2005.0411.

6Palagi, E., Leone, A., Mancini, G., & Ferrari, P. (2009). Contagious yawning in gelada baboons as a possible expression of empathy Proceedings of the National Academy of Sciences, 106 (46), 19262-19267 DOI: 10.1073/pnas.0910891106.

7Joly-Mascheroni, R., Senju, A., & Shepherd, A. (2008). Dogs catch human yawns Biology Letters, 4 (5), 446-448 DOI: 10.1098/rsbl.2008.0333.

Dolphin Curiosity: Knowledge for Knowledge’s Sake

You’ve just finished a delicious sushi dinner and you’re stuffed; you couldn’t possibly eat another bite. Still, when the diners next to you are served, you can’t help looking over, just to make sure that they, the other dolphins, aren’t getting a better meal.

That’s right, you’re a bottlenose dolphin, and you’re curious. Curious not because you’re going to do anything about it, but simply because you want to be sure that you haven’t missed out on anything. You want knowledge for knowledge’s sake, however painful it might be.

Humans often need to know certain things, even when finding out opens the doors to an unpleasant discovery. After the worker receives a raise, he can’t help poking around to see whether his coworker received a larger increase. After the shopper buys a large flat screen TV, she keeps looking at advertising circulars to see whether she paid too much. While our curiosity sometimes serves a clear purpose (perhaps that raise can still be renegotiated, maybe that TV can be returned), we often persist in our quest for potentially negative information even when it is too late to change anything, even after the raise has been formally accepted and the TV can no longer be returned. Research on human-decision-making suggests that we act this way because we find the uncertainty of “not knowing” to be uncomfortable. Finding out even the most-unpleasant truths can relieve us from ruminating obsessively over our suspicions, enable us to make sense of our missed opportunities, assist us in coming to terms with our past decisions, and ultimately allow us to regulate our moods in a healthy fashion.

But dolphins? The actions of nonhuman animals are not typically described in these terms. Rather, we find utilitarian explanations – a tangible benefit to compensate the animal for the energy and risk of exploration, a way in which the animal’s curiosity will improve its fitness or survival chances.

OMG, do you see what the Snorkersons are having for dinner?! (image credit: Peter Asprey)

Recently, though, a research team from Israel reported in the Journal of Economic Psychology on a clever experiment indicating that bottlenose dolphins (Tursiops truncatus) are much like humans in seeking knowledge for knowledge’s sake. The researchers studied a group of eight bottlenose dolphins at a “commercial sea enclosure” as they were fed over a seven-month period. The dolphins were fed meals of varying size five times a day, with all dolphins eating at the same time. The dolphins were fed from three separate rafts, with each dolphin assigned one of the rafts and summoned to the proper feeding location with a specific sound signal. During the study period, the researchers observed a total 1,250 dolphin feedings and made special note whenever a dolphin went to over to another raft to explore what other dolphins were being fed.

One of the researchers’ hypotheses was that, to the extent the dolphins sought out knowledge for knowledge’s sake (described in the paper as “Non-Instrumental Curiosity”), they would increase this behavior once their basic survival needs had been satisfied. The researchers were assisted in exploring this hypothesis by two factors: first, about halfway through the study, the dolphins were put on a diet, receiving approximately 15% less food per day on average for the remainder of the testing period, and second, during the latter portion of the experiment the dolphins’ sexual interactions increased markedly due to higher water temperatures and seasonal changes. (Note to self: watch out for pods of horny dolphins as the impacts of global warming become more severe.)

The researchers found that, over the course of the experiment, dolphins visited other feeding rafts 26% of the time (325 of 1,250 feedings). All dolphins visited other rafts, but the percentage of visits ranged from 11.3% to 37.9%, indicating individual differences in curiosity among dolphins. Because the dolphins managed to obtain food scraps on only three occasions (i.e., less than 1% of the time), the research team concluded that it wasn’t likely that the dolphins were using their explorations as a foraging strategy. Moreover, the researchers statistically analyzed the explorations and did not find correlations between the visiting behavior and the dolphins’ known social structure (that is, associations between mothers and calves, adolescent males and females, etc.). In short, there were no obvious benefits to the dolphins’ behavior, and the results supported the premise that they were visiting other feeding rafts out of Non-Instrumental Curiosity.

Hrmph... Next time let's put the researchers on a diet, and see how it impacts *their* behavior (image credit: Laaude at fr.wikipedia)

In addition, the researchers found that dolphins were significantly more likely to visit other rafts when they received larger meals, and that their overall curiosity level was much lower during the phase of the experiment when they were on a diet (they visited other rafts only 13% of the time when on a diet, compared to 38% of the time during the non-dieting phase). Further, during the dolphins’ more sexually active phase, they significantly decreased their exploratory behavior — they visited other rafts only 12% of the time during this phase, compared to 43% during the period when they were less sexually active. (Note though that, because there was a substantial overlap between the dieting and sexually active phases, it wasn’t really possible to separately tease out the relative impacts of these two factors.)

The researchers summarized their results as follows:

In this manuscript, we show that bottlenose dolphins as well, sometimes seek to increase their knowledge concerning food allocated to other dolphins in the group, even though such knowledge could not increase self-food availability. This search increases when own feed is augmented, and decreases when sexually engaged (a competing basic need to food and curiosity), suggesting that knowledge for knowledge’s sake emerges particularly when the organisms’ basic needs (e.g., food) have been satisfied, allowing higher-level psychological needs to emerge.

It seems to me that another way to look at Non-Instrumental Curiosity is that it may be an indication that dolphins are sensitive to inequity and that they possess a sense of fairness, and that it would be interesting to see further research into related cognitive realms, such as their capacity for altruism, empathy and self-awareness. While that may be the subject of future experiments and later AnimalWise posts, for now I’m kind of curious – where did you get all of that tasty looking mackerel?

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ResearchBlogging.orgShani, Y., Cepicka, M., & Shashar, N. (2011). Keeping up with the Joneses: Dolphins’ search knowledge for knowledge’s sake Journal of Economic Psychology, 32 (3), 418-424 DOI: 10.1016/j.joep.2011.02.014.

Back to the Future – Mental Time Travel in Tropical Birds?

I may not have a nuclear-powered DeLorean parked in my driveway, but I can travel in my own personal time machine anytime I want, and so can you.

Through what’s known as mental time travel, or MTT, you can move backwards and forwards through time – visiting the past when you remember a specific event you’ve already experienced, and then zipping forward to the future as you use this memory to predict, plan for and shape events that are yet to come.

Mental time travel is no mean feat: it implicates sophisticated cognitive processes and is thought to form the foundation for advanced forms of consciousness such as self-awareness and the ability to attribute independent thought, desires and intentions to others (an ability sometimes referred to as “theory of mind”).

So, can other animals engage in mental time travel? Perhaps not surprisingly, this has been a controversial topic, and many have argued that we humans are the only ones able to mentally flit about the fourth dimension, leaving all other animals stuck in the here and now. Although this may be partly attributable to our anthropocentric world view1, the language barrier between humans and other animals also poses a real problem, as it’s difficult to design MTT experiments that don’t involve interviews, since the best time travel evidence may consist of the voyager’s personal and subjective reports of the experience. Accordingly, solid evidence for MTT in other animals has been limited, and much of the evidence that does exist consists of anecdotal accounts and a small number of experiments involving great apes and western scrub-jays.

In a paper2 published in the October 14, 2011, issue of Behavioral Ecology, though, a research team led by Corina Logan of the Department of Experimental Psychology at the University of Cambridge proposed an intriguing new avenue for further research, one that might significantly expand the number of species that may be tested for MTT abilities. More specifically, Logan and her colleagues identified a specialized strategy among birds – army ant bivouac checking – that may provide conditions in the wild that could favor the development of mental time travel in a variety of species.

If I go back in time and shoot my grandmother, does that mean I’ll never be born?? (White Whiskered Puffbird, credit Glenn M. Duggan FZS)

While many tropical rain forest birds earn an opportunistic living by gobbling up insects and other small invertebrates flushed out of hiding by army ants on food raids, a subset go a step further – after raids by a specific army ant species (Eciton burchellii), these birds follow the ants back to their temporary nests (known as a bivouacs) in the evening, and then return to check on the bivouacs the next morning before the ants raid again. To date, twenty one different “bivouac-checking” bird species have been identified.

Tracking army ant bivouacs is more complicated than one might think. As the ants raise their young, they cycle through two distinct phases: one (approximately 20-day) phase during which they remain in a set location, conducting most of their raids at the beginning and end of the phase and relatively few during the middle two weeks; and a second (approximately 14-day) nomadic phase, during which they move their bivouac on a daily basis and conduct raids almost every day.

Aren’t you hungry? We haven’t eaten since tomorrow. (Ocellated Antbirds, credit PhilSlosberg)

From the perspective of a bivouac-checking bird seeking a reliable food source, these varying phases are significant. When the ant colony is stationary, it may be relatively easy to find, but its raids will be sporadic; when the colony is nomadic, it may be more difficult to find, but its raids will be quite regular. Clearly, a bird will do better if it can keep track of multiple stationary colonies that conduct raids only sporadically, if it can quickly find nomadic colonies based on their prior locations and previous movements, and if it can remember whether particular colonies are in phases in which they’re likely to conduct raids.

The researchers identified these conditions as providing a potential testing ground for MTT. While the birds obviously can’t be interviewed, their environment may elicit behavior that shows that they have an “episodic-like memory” (that is, they can recall the what-where-when aspects of past events) and that they can take action in anticipation of future motivational states independent of their current needs (that is, they can plan flexibly for the future).

After noting that the birds appear to form specific memories about locations (since they return in the morning after evening bivouac checks), the researchers hypothesize that the birds may remember which colonies are in which locations and what phase the colony is in, “and that they may be using episodic-like memory if they prefer to check those bivouacs from army ant colonies in the nomadic phase.” Moreover, they continue:

Time travel jokes never get old! (Spotted Antbird, credit Mike Danzenbaker)

We suspect that future planning could be involved in bivouac-checking bird behavior because birds check bivouacs when sated (conferring no immediate benefit), a behavior that does not make sense until the next morning on return to the bivouac when the bird finds the ants raiding again and encounters its next meal (a delayed benefit). Because bivouac checking occurs after foraging at a raid, there is no immediate benefit to conducting this behavior in terms of acquiring a meal in the next few minutes. Instead, the benefit occurs the next morning when the ants begin raiding again; bivouac-checking birds return and are the first to begin foraging at the raid. This could indicate a dissociation between their current state (sated) and a future need (will need to eat tomorrow), which suggests anticipation of future events. (Citations omitted.)

Logan and her colleagues call for additional field research and, if their hypotheses are supported, laboratory experiments that will enable experimenters to vary bivouac locations and colony phases under controlled circumstances, and to determine whether the birds use specific memories and flexible future planning or whether they engage in automatic behavior using vision, smell, circadian rhythm or other cues in checking on bivouacs.

At this point, the researchers’ hypotheses need additional experimental support, but it’s already clear that they’ve made some keen observations about specialized behavior in the wild and have opened the door to substantially expanded testing for mental time travel in animals. As more researchers come up with similarly elegant ways of investigating abilities previously thought to be unique to humans, I think we will see additional barriers fall.

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1As regular readers know, this is a recurrent AnimalWise theme. Time and again we humans have claimed that we are the only ones to have a particular skill, only to discover later on that, in fact, many animals may share the same or comparable abilities with us. Prior posts have discussed this phenomenon in areas including tool use (many different fish, crested rats, ants, dolphins, chimpanzees, crows), language (bees and prairie dogs), analogic reasoning (capuchins and baboons), grief and mourning in various animals, and self-recognition (dogs, magpies).

ResearchBlogging.org2Logan, C., O’Donnell, S., & Clayton, N. (2011). A case of mental time travel in ant-following birds? Behavioral Ecology DOI: 10.1093/beheco/arr104.

The Wisdom of the Aged: Matriarch Elephants Lead with Experience

As many people know, African elephants (Loxodonta africana) live in complex matrilineal societies, with closely-knit family groups led by a matriarch who is typically the oldest and largest female in the family. In order to appreciate the importance of these matriarchs, it may help to first consider a traditional Japanese folktale:

Once there was an arrogant young village lord who, deciding that old people were useless, banished them to the mountains to die. Although the villagers were distressed, they obeyed rather than face severe punishment. One young farmer couldn’t bear to follow this cruel decree, though, and hid his aged mother away in a safe and secret room.

Several years later, an invader arrived, announcing that he’d spare the village only if three tasks could be performed. First, he must be presented with a box containing one thousand ropes of ash. Next, a silk thread must be drawn through a small hole that bent seven times along the length of a log. Finally, he must be given a drum that sounded without being beaten.

In each case, the village lord offered rewards, cajoled and threatened the townspeople, but nobody knew what to do; all were in despair. The tasks all seemed impossible. Each time, though, the farmer asked his mother and she knew the answer: soak ordinary rope in salt water before burning it; tie the silk thread to an ant at one end of the hole and place sugar at the other; put a bumblebee in a drum and it will buzz as it tries to escape. The village was spared.

Ultimately, the lord finds out that they have all been saved by the wise old mother, and from that time on elders in the village are revered.

Shifting scenes now from the mountains of long-ago Japan to the plains of today’s Africa, it turns out that older matriarch elephants are much like the heroic old Japanese mother – they are the ones with the answers, the ones that can save their fellow elephants from outside threats with the wisdom they have accumulated through experience.

Listen to your Grandmother! (image copyright ElephantVoices)

As we know from the decades of observation and research performed by Cynthia Moss and her colleagues in Kenya and Tanzania, matriarch elephants act as group leaders, holding together their families and providing behavioral guidance during times of crisis. Many observers believe that the oldest matriarchs – those with the most experience and greatest ecological knowledge – make the best decisions, but until recently it has proved to be difficult to quantify the relevant skills in a manner conducive to experimental testing.

In a March 2011 paper published online in the Proceedings of the Royal Society B, however, a team of scientists led by Karen McComb of the University of Sussex reported on a clever set of experiments that tested whether older Amboseli National Park matriarchs were better than their younger counterparts at assessing the perceived threat posed by various lion roar recordings.

While African elephants are able to fend off most natural predators, they have to watch out for lions, who occasionally prey upon younger calves. Also, even though lionesses perform the, ahem, lion’s share of the hunting for the pride, male lions actually pose a greater threat to elephants. Male lions, despite their generally well-deserved reputation for laziness, are, on average, half again as large as females and much stronger, giving them a better chance of overpowering a vulnerable young elephant.

Accordingly, the researchers assembled lion “playbacks” in four separate categories – single female roars, single male roars, three female group roars and three male group roars – which they then played to 39 elephant family groups over a period of slightly more than two years. Because of the extensive demographic information compiled by the Amboseli Elephant Research Project, they knew the age of the matriarch in each of the 39 families.

After playing the different roars, the researchers analyzed video of the elephants’ responses, focusing particularly on the behavior of the matriarchs. They documented specific defensive reactions, including prolonged listening to the roars, whether the family bunched around the matriarch after hearing the roars, the speed and intensity of any bunching behavior, and whether the matriarch changed her direction and moved toward the source of the playback.

Here are two brief videos, one showing an elephant family reacting to lion roars and the other narratively describing the reactions as reflected in still images:

After recording all of the responses, the research team performed statistical analyses and sorted their results by matriarch age. They found that, while matriarch age did not have an impact on how the elephants reacted to varying number of lions (all elephant families consistently ratcheted up the intensity of their response when the number of lions roaring went from one to three), it did have a strong impact on the elephants’ response to the more serious threat presented by male lion roars, with male roars leading to more prolonged listening and intensive defensive bunching in families led by older matriarchs.

As the researchers put it:

Our work provides the first direct experimental evidence that older matriarchs are in fact able to make better decisions when faced with ecological challenges — in this case, the presence of dangerous predators. It thus bridges an important gap between theoretical predictions about how knowledge might be expected to affect leadership and empirical studies, which to date have been largely confined to observational accounts.

Based on these findings, I’m quite confident that the older matriarchs will do quite well on their next set of tasks involving burning ropes, crooked logs and drums. Now, if only that was enough to keep humans from invading their villages….

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ResearchBlogging.org

The Japanese folktale can be found, among other places, in The Wise Old Woman/retold by Yoshiko Uchida; illustrated by Martin Springett. ISBN: 0689505825.

McComb, K., Shannon, G., Durant, S., Sayialel, K., Slotow, R., Poole, J., & Moss, C. (2011). Leadership in elephants: the adaptive value of age Proceedings of the Royal Society B: Biological Sciences, 278 (1722), 3270-3276 DOI: 10.1098/rspb.2011.0168.

Analogical Reasoning in Animals

In today’s post, I’d like to explore some surprising recent findings about the abilities of animals in the area of analogical reasoning.

Reasoning by analogy is central to the way we think, enabling us to use familiar concepts to solve new problems. When a catastrophic event strikes Wall Street, economists inevitably point to analogous historical disruptions in their attempts to predict whether we’re facing long-term troubles or a quick recovery. When lawyers advocate on behalf of clients in new realms such as digital media, they often ground their arguments in principles that evolved centuries ago to protect real property interests. When scientists explain the motion of molecules and other phenomena that we cannot directly perceive, they frequently turn to concrete examples such as colliding billiard balls or streams of water.

On a more mundane level, analogical thinking underlies many of our idioms and permeates our everyday language. Think how lost you’d be if you were suddenly unable to understand phrases that explicitly or implicitly apply concepts from one context to events or actions in another. Conversations at work would confuse you (more than usual). Your boss’ suggestion that you take some time off to recharge your batteries would leave you scratching your head rather than looking for deals on tropical island vacations. You wouldn’t be able to follow political discussions (oh no!). You’d be the only one asking “oh my god, was it with guns or knives?” after hearing that one candidate outdueled another in a debate. You’d be the only one worrying about cannibalism after learning that the people were hungry for new leadership. You’d find sports to be newly upsetting, as you’d literally go into mourning after learning of your favorite team’s fatal missteps. (Ok, I take that back – nothing has changed here, especially for Boston Red Sox fans.)

Relational Matching Tests

One of the most common tests used to assess an individual’s ability to solve analogy problems is known as relational matching-to-sample or RMTS. In its classic form, RMTS involves first showing the subject a sample set consisting of two or more objects that are either identical (for example, two circles) or nonidentical (for example, a square and a circle). Sets containing identical objects are sometimes referred to as reflecting the “identity relation” and those containing nonidentical objects are said to reflect the “nonidentity relation.” Next the subject is shown two comparison sets containing novel objects, one embodying the identity relation (e.g., two triangles) and the other the nonidentity relation (e.g., a rectangle and a triangle). To succeed, the subject must choose the comparison set that matches the relationship demonstrated by sample set. For instance, the correct choice for a subject shown two circles in the sample would be the comparison set containing the two triangles, whereas the correct choice for the subject initially shown the square and the circle would be the comparison set containing the rectangle and the triangle.

RMTS is particularly well suited for testing the abilities of non-human animals, as it poses an analogy problem in a strictly visual manner, not relying in any way on linguistic skills. In essence, success requires the subject to not only make a “first order comparison” between same and different, but also to make a “second order comparison” by applying this underlying distinction to a novel environment. Many researchers consider this ability to lie at heart of analogical reasoning.

A “Profound Disparity”?

Until recently, studies have suggested that humans and a select few great apes stand far apart from all other animals in terms of analogical reasoning abilities. While many animals can successfully distinguish between same and different shapes or colors, they tend to struggle when it comes to making second order comparisons of the sort required by RMTS tasks. Since only humans and some chimpanzees, gorillas and orangutans have performed well at RMTS testing, researchers have proposed that a “profound disparity” exists between the analogical reasoning capacity of hominids and other animals.

For example, several studies have shown that some baboons and pigeons can learn to pass RMTS tests if they involve large-sample and comparison sets (e.g., comparisons involving 4 x 4 grids of 16 all identical and 16 all different objects), but that their performance rapidly deteriorates as the size of the grid decreases as well as when the distance between the objects in the grid increases. According to researchers, one reason why animals do better with larger sample sets may be that there’s a greater amount of variation or “entropy” between non-analogous grids in larger sample and comparison sets, which makes the task of distinguishing between potential answers easier.

Notwithstanding these prior findings, however, two studies published in the last few months now pose a challenge to the “profound disparity” concept, suggesting that a suitable testing environment can showcase robust analogical reasoning skills in non-apes.

Clever Capuchins

In the first study, which was published in PLoS ONE in August 2011, researchers led by Valentina Truppa and Elisabetta Visalberghi of the National Research Council in Rome, Italy, found that New World tufted capuchin monkeys (Cebus apella) were capable of solving RMTS tasks involving sample and comparison sets involving sets of as few as two objects.

What are all of those freaking squiggles in that diagram above my head? (image credit: Charlesjsharp)

The research team studied five capuchin monkeys, testing them over and over again on RMTS tasks involving varying numbers of icons. While the specific tests varied, the general approach was to start by giving the monkeys trials involving a relatively small pool of different icons and, only if and when a monkey achieved proficiency (as measured by percentages of correct answers) over the course of thousands of trials, to introduce novel icons for comparison. Also, in one of the experiments, if the monkey did not ultimately reach the proficiency threshold on a two-icon comparison test, “entropy” was increased and the monkey was given an easier four-icon test.

Ultimately, after a total of 21,888 trials (yes, that’s correct!) one of the five capuchins, Roberta, proved to be a real overachiever. As the researchers put it:

The current study demonstrates the acquisition of abstract concepts based on second-order relations by one capuchin monkey, Roberta. She was first successful with four-item stimuli and then with two-item stimuli, the latter being the most difficult condition previously thought to be mastered only by apes. Since her performance was robust across different types of stimuli and well above that of the other subjects, we can argue that relational analogies are very difficult for capuchins, but under specific circumstances not impossible.

Way to go, Roberta!

Bright Baboons

In a second study, published on September 20, 2011, in Psychological Science, a research team headed by Joël Fagot of the Centre National de la Recherche Scientifique at the Université de Provence reported that guinea baboons (Papio papio) can learn to perform surprisingly well at RMTS tasks … and then retain this ability over a 12-month period. In this study, 29 baboons with no language training and little or no experience with relational matching tests participated in various RMTS experiments involving geometric shape comparisons.

All this RMTS stuff gives me a headache (image: Animal Globe)

The first experiment consisted of classic RMTS trials, each involving a sample set made up of pairs of identical or nonidentical geometric shapes, and two comparison sets with new geometric shapes, with only one of the comparison sets matching the relationship demonstrated by the sample set. At first, the testing pairs were selected randomly from among 10 geometric shapes, but once a baboon had achieved an accuracy level of 80% or better in three consecutive sessions of 100 trials, new geometric shapes were introduced up to a maximum of 90 shapes by the end of the experiment. Six of the 29 baboons were able to make it to the 80% threshold level, and five were ultimately able to proceed through testing until they reached all 90 shapes.

The second experiment included changes designed to make the challenge more difficult: the geometric shapes were moved further apart and, perhaps more significantly, in half of the tests the “incorrect” comparison pair, rather than containing all new geometric shapes, actually contained one of the shapes from the sample pair. In other words, even though this comparison pair was incorrect from the standpoint of analogy testing, it contained a shape that was directly linked to the sample set, potentially confusing the baboon if it was focused on the similarity of the shapes rather than the conceptual relationship between the shapes.

In spite of the enhanced degree of difficulty, all five of the baboons who participated – the same baboons who had been successful in the first experiment – performed at above chance levels throughout the second experiment (although, not surprisingly, their performance tailed off somewhat in the trials where the incorrect response shared a shape with the sample set).

Finally, the research team retested the five successful baboons in accordance with the first experiment methodology after a one-year lapse during which the baboons had no practice at RMTS tasks. All five baboons reached the 80% success level far more quickly than they had the first time around, providing strong evidence that they had been able to retain their relational matching skills over this one-year period.

As with the capuchin monkeys, the baboons were not naturals at these tests – they went through thousands upon thousands of trials and only gradually acquired their relational-matching skills. Once again, though, the research strongly suggests that there is not a bright line “profound disparity” between the capabilities of hominids and those of other animals, and that other animals can demonstrate the cognitive foundation necessary for abstract analogical reasoning.

So, as in other areas, the more we explore the abilities of animals, the more we find that we have been wrong about what we thought were cognitive barriers. As we become more adept at designing experiments that are patiently conducted and thoughtfully tailored to the skills and natural adaptations of the specific animals we are studying (rather than the skills and adaptations of college undergraduates), we should continue to see the breakdown of additional barriers.

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ResearchBlogging.orgTruppa, V., Piano Mortari, E., Garofoli, D., Privitera, S., & Visalberghi, E. (2011). Same/Different Concept Learning by Capuchin Monkeys in Matching-to-Sample Tasks PLoS ONE, 6 (8) DOI: 10.1371/journal.pone.0023809

Fagot, J., & Thompson, R. (2011). Generalized Relational Matching by Guinea Baboons (Papio papio) in Two-by-Two-Item Analogy Problems Psychological Science, 22 (10), 1304-1309 DOI: 10.1177/0956797611422916

The Orange-Dotted Tuskfish Strikes Back: Movie Shows New Species of Fish Using Tool

AnimalWise Update

Recently, the blackspot tuskfish (Choerodon schoenleinii) became a media sensation when it was captured in photos using a rock as tool to open a clam. Apparently not happy with the print media attention afforded to its relative, the orange-dotted tuskfish (Choerodon anchoago) has taken the behavior to the movies, digging up a clam with its pectoral fin, swimming about five meters with it, and then crushing it open using a rock as an anvil:

As reported in the latest issue of Coral Reefs, a diver off the coast of Palau observed the orange-dotted tuskfish using a rock as a tool on three separate occasions, capturing the above footage on the final instance. The paper notes that three separate genera of wrasses (the Choerodon that have been in the news lately, as well as the Halichoeres and Thalassoma) have now been seen using similar sideways head movements to slam bivalves against rock anvils, suggesting that this may be a “deep-seated behavioral trait” in wrasses and, potentially, other groups of fishes.

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ResearchBlogging.orgBernardi, G. (2011). The use of tools by wrasses (Labridae) Coral Reefs DOI: 10.1007/s00338-011-0823-6

Converging with Canines: Are Humans and Dogs Evolving Together?

In our man-made world, it can feel like everything is converging all at once. Indistinguishable glass skyscrapers sprout up in cities all over the globe, near identical car models vent carbon dioxide into the air on different continents, and people around the world see their waistbands expand as they gulp down the same McFood. Global economies are more connected than ever, with natural disasters in Japan, sovereign debt issues in Europe, and rumors of Wall Street misdeeds shaking worldwide markets within minutes. Even the social media that deluge us with information seem like they’re growing more and more alike, as we now drown in unending streams of look-alike feeds, postings, messages and links from Twitter, Facebook, Google+ and others.

You may wonder whether the forces of convergence are a recent phenomenon, a product of human technology, or whether they may have deeper roots in the natural world. In fact, convergence can and does occur in the realm of biological evolution, albeit at a more comfortable pace. For example, “convergent evolution” occurs when different species independently evolve similar solutions to comparable evolutionary pressures. A classic example of this is the development of wings and the ability to fly by birds, bats and pterosaurs:

Diagram of wing morphology and/or and comparative network hub structure of Twitter, Facebook and Google+ (image credit: National Center for Science Education)

Consider also the independent evolution of sleek, torpedo-shaped bodies by fish, cetaceans and ichthyosaurs:

Sleek ocean swimmers (image credit: All About Reptiles)

Closer to home, scientists at the Max Planck Institute for Evolutionary Anthropology have concluded that we may be undergoing a process of cognitive convergent evolution with dogs based on our social relationships over thousands of years with these “best friends” of ours. In a paper published in Trends in Cognitive Sciences, Brian Hare and Michael Tomasello reviewed a large number of studies focused on canine, human, and non-human primate social and communicative skills and reached some interesting conclusions.

Proof of convergent canine-human evolution (source unknown)

They began their analysis by focusing on research showing how well domestic dogs do at interpreting human social and communicative behavior. For example, dogs excel at tests in which experimenters hide food in one of several opaque containers and then signal where it has been hidden by pointing, gazing, bowing or nodding, or placing markers in front of the target location. The dogs easily interpret this type of cue, passing tests such as these on the first attempt and performing correctly even when humans try to trick them by walking towards the wrong container while pointing in the opposite direction to the correct container.

Also, studies have shown that dogs are aware of what humans can see. For instance, if a human turns around during a game of fetch, the dog will almost invariably bring the ball back around the human and drop the ball in front of his face. Similarly, dogs have shown that they prefer to beg for food from humans whose eyes are visible than from ones whose eyes are covered with a blindfold or bucket, but are more likely to approach forbidden food when a human’s eyes are closed.

Indeed, dogs actually consistently outperform chimpanzees and other primates at these types of skills, even though, in areas of non-social cognitive performance, dogs do not do so well. For example, non-human great apes are much better at making inferences about the location of hidden food based on non-social cues (such as a tilted board that might be tipped up by hidden treats) and at tests that require them to achieve food rewards by, for example, reeling in food attached to strings.

With this in mind, Hare and Tomasello turned to whether domestic dogs’ specialized social skills are likely to be due to convergent cognitive evolution with humans or whether another explanation is more plausible.

First, they considered the possibility that dogs learn to recognize human social cues based on their experiences growing up in human households. They found, however, that studies show that even puppies as young as nine weeks old are adept at solving problems using human pointing and gaze cues, and that puppies raised without much exposure to humans are equally skilled at interpreting these cues.

Then, they considered whether domestic dogs may have simply inherited their social skills based on their common ancestry with wolves, since wolves are, after all, pack hunters who need to be able to follow complex social interactions with other wolves and with prey. However, although wolves are generally equal to or better than domestic dogs at memory tests and tasks involving general problem-solving abilities, wolves (even those raised by humans) are simply unable to match the performance of dogs at spontaneously using human social cues to solve problems.

Next, the researchers sought evidence for the evolution of social skills in dogs through their long-term relationship with humans. They looked at a population of domesticated foxes, where the selection for breeding had been based solely on the tendency of individual foxes to be non-aggressive and fearless around humans. Interestingly, these foxes were just as adept as dogs in using and interpreting human social cues, and far better than a population of control foxes that had been bread randomly with respect to their attitude towards humans.

Based on all of these comparative findings, Hare and Tomasello concluded that the best explanation for dogs’ specialized social skills is that they evolved as a consequence of dogs having been domesticating by humans, representing a case of convergent cognitive evolution. Interestingly, Hare and Tomasello went further and, based on their review of the research on domesticated foxes, concluded that the evolution of specialized social skills in domesticated dogs may actually have been an incidental byproduct of an initial decision to select based solely on nonaggression (as opposed to social intelligence).

Finally, turning to primate evolution, Hare and Tomasello speculated that a similar process may have contributed to differences between human and chimpanzee social skills. Under what they refer to as the “emotional reactivity” hypothesis, they predicted that differences in temperament between humans and other primates may help explain some of humans’ extraordinary social cognitive abilities. They point to studies showing that chimpanzees’ willingness to cooperate with each other can often be limited by lack of social tolerance for one another resulting from fear and/or aggression, and contrast this to a more socially tolerant temperament that may ultimately have enabled our hominid ancestors to develop flexible forms of cooperation and communication. In other words, humans underwent a form of self-domestication leading to greater social abilities, thereby convergently evolving with our canine companions who were undergoing the same process.

I’m not sure I entirely buy the notion that we humans are so exceptionally tolerant, but I have noticed that you’ve started to look a bit like your dog. In a future post, we may look at whether we may also be evolving to be more like members of the cat family:

Which one is the lion? (source unknown)

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ResearchBlogging.orgHare, B., & Tomasello, M. (2005). Human-like social skills in dogs? Trends in Cognitive Sciences, 9 (9), 439-444 DOI: 10.1016/j.tics.2005.07.003

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