Canine Comprehension of Complex Communications

No question about it, canines are smart and adaptable. In recent posts, we’ve featured a dingo who cleverly figured out how to use a table as a tool enabling him to reach tempting food, described research suggesting that dogs may be so in tune with our feelings that they can catch yawning bouts from us, highlighted evidence that humans and dogs may be undergoing cognitive convergent evolution with each other based on our close social relationships over the millennia, and even noted a study pointing to canine self-awareness based on their recognition of their own, er, yellow snow.

Also, dog owners frequently describe how smart their cold-nosed friends are, how they know the words for large numbers of toys and other objects, and how they understand and sometimes obey numerous commands. (Good dog!) However, while there have been many studies investigating the linguistic abilities of primates, cetaceans, parrots and certain other species, there has been surprising little formal research into the verbal comprehension of dogs. Dogs have been tested for their understanding of specific words and commands, but there has been an absence of research into whether they can understand and distinguish the constituent parts of complex sentences that refer both to objects (e.g., “ball,” “stick” or “newspaper”) and to actions (e.g., “fetch,” “roll over,” or “point”).

Until recently, that is.

Chasing Down Linguistic Meaning

First, in 2011, John Pilley and Alliston Reid published a paper in Behavioural Processes detailing a variety of word comprehension tests that they had given to Chaser, a rock star border collie famous for knowing the names of over 1,000 objects.

In one of these experiments, Pilley and Reid tested whether Chaser could independently understand the meanings of verbs and nouns. In this test, Chaser was asked to respond appropriately when three different commands (take, paw, and nose) were randomly associated with three different stuffed cloth toys (Lips, a toy resembling human lips; ABC, a cloth cube with those letters written on its side; and Lamb, a stuffed lamb) in 14 independent trials using a double-blind procedure. Chaser was familiar with the commands, but none of the three toys had ever been paired with any of the commands prior to the experiment.

The three toys were lined up on a soft pad in front of a one-meter high cloth barrier. During the trials, neither Chaser nor the experimenter could see each other, as the experimenter knelt on one side of the barrier, with Chaser hanging out with the toys on the other side. The experimenter, who had been given a toy and command combination generated with a random number table, gave Chaser his instructions, while a confederate sat to the side where she could see Chaser perform and signal to the experimenter with a hand wave when the trial was over. Here’s a picture of the setup, taken before the experimenter retreated to the other side of the barrier to commence the trial (note that the confederate’s legs are visible to the right of the picture):

The tests were videotaped with sound recording, with three independent raters (not the experimenter or the confederate) scoring whether Chaser chose the correct toy and performed the correct command. Each rater first watched the videotape with the sound turned off (so he/she wouldn’t know which instructions had been given to Chaser), and recorded which command was actually executed towards which toy. After rating all 14 trials, the rater then watched each trial again with the sound turned on in order to assess whether Chaser’s behavior accurately matched the instructions given by the experimenter.

How did Chaser do? Perfectly.

There was absolutely no disagreement among the raters – each judged Chaser to be 100% accurate across the 14 trials, performing the correct command to the correct toy as instructed. As Pilley and Reid put it:

These results clearly support the conclusion that Chaser understood reference – that the verbal noun of an object referred to a particular object with distinct physical features independent of actions directed toward that object.

Comprehending Sentences

Then, earlier this month, Daniel Ramos and Cesar Ades of the University of São Paulo published a study in PLoS One that extended the Chaser research.

In their study, Ramos and Ades tested Sofia, a female mongrel dog, on two-item requests over a two year period, starting when she was a two-month old puppy. The testing consisted of eight progressive phases, during which Sofia first learned some basic vocabulary and then gradually faced increasingly complex tests of her comprehension abilities. The specific phases were as follows:

  1. Learn the names for four objects (ball, key, bottle and stick) and two requests (point or fetch).
  2. When presented with two objects, approach the correct object on request, or perform the correct action upon request.
  3. Perform object and action requests in sequence – that is, first approach the proper object after being given an initial “object request” and then, after being given an “action request,” perform the correct action on the object.
  4. Perform single multi-part requests – that is, after being given a compound request (e.g., ball fetch, ball point, key fetch, key point, bottle fetch and stick point), approach the correct object and perform the correct action.
  5. To eliminate the possibility of inadvertent cues from the experimenter, perform the same tests as in phase 4 but with the following control variations: (1) experimenter wearing sun-glasses, (2) experimenter with mouth covered by a cloth band, (3) research assistant absent from the room, (4) unfamiliar person as experimenter, (5) testing in an unfamiliar room, (6) test objects scattered, distant from one another, and (7) new objects of the same category (new balls, keys, etc.) offered.
  6. Perform reversed multi-part requests – that is, in response to compound requests in which the word order has been switched from object-action to action-object (e.g., fetch ball, point ball, fetch key, point key, fetch bottle and point stick), approach the correct object and perform the correct action just as in phase 4.
  7. Perform multi-part requests with a new, previously-untested object, a teddy bear.
  8. Perform multi-part requests with new combination object-action pairs (stick fetch and bottle point) that had not been used at all during prior training or tests.

And how did Sofia do? Well, she wasn’t perfect like Chaser, but she was pretty impressive. Her success rate was significantly above chance in all phases except for the final one, in which she had only 3 out of 10 correct responses for both the stick fetch and the bottle point requests. Notwithstanding this one area of underperformance, Ramos and Ades concluded:

Our results suggest that dogs share with “linguistic” animals the capacity to encode in memory at least two heterogeneous items of information to be used in subsequent directed performance, a capacity which, although far from being “an infinite use of finite means” as human grammars are, may have comparative relevance as a forerunner to syntactical functioning.

Now, I know what you are saying. Yes, your dog can do that too. I’m aware that she consistently beats you and your friends at poker, and I’ve seen the video where she plays charades while riding around your house on a Roomba.

You see, that’s actually the issue. Dogs are incredibly good at picking up human signals, which is why carefully-designed experiments are important in ruling out the “Clever Hans” effect (named after a horse who, more than a century ago, amazed crowds with his apparent mathematic abilities, but who was ultimately found to be picking up on involuntary body language cues from his trainer).

By eliminating visual contact between Chaser, Sofia and the experimenters and by adding controls such as having unfamiliar persons issue requests and moving around the objects, the researchers ensured that the dogs had to rely exclusively on words rather than on inadvertent human signals or other contextual clues. By changing the size, shape and color of the requested objects and introducing a new object (the teddy bear), the researchers were able to test whether Sofia was able to generalize and apply concepts to new objects in the same category. By reversing word order and thereby changing the acoustics of compound requests, the researchers were able to rule out the possibility that Sofia was performing based on memorizing the sound properties of requests rather than actually understanding the individual words comprising the requests.

So, you were right all along – your dog really does understand you. The problem is everyone else.

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ResearchBlogging.orgPilley, J., & Reid, A. (2011). Border collie comprehends object names as verbal referents Behavioural Processes, 86 (2), 184-195 DOI: 10.1016/j.beproc.2010.11.007.

Ramos, D., & Ades, C. (2012). Two-Item Sentence Comprehension by a Dog (Canis familiaris) PLoS ONE, 7 (2) DOI: 10.1371/journal.pone.0029689.

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Born This Way? Gender-Based Toy Preferences in Primates

Last week, British parents who had hidden their child’s gender from the world finally revealed that their five year old, now ready to enter school, is a boy. While the parents had hoped to raise their son Sasha in a gender-neutral way (“Stereotypes seem fundamentally stupid. Why would you want to slot people into boxes?”), their approach raised eyebrows and controversy. Were they creating an environment where their child could find his own gender identity, free from crippling societal expectations, or were they conducting a bizarre and possibly harmful experiment on a family member?

Putting aside the issue of whether the parents acted appropriately, the story raises fascinating questions about gender-specific traits and preferences. To what degree are gender differences innate and biological, and to what extent do they arise out of societal modeling and environment?

Some (including Sasha’s parents) may see gender preferences as being primarily influenced by human social pressures, but there are indications of biological influences as well. For example, girls with a particular genetic condition that exposes them to high prenatal levels of androgen often show “masculine” toy preferences, even when their parents strongly encourage them to play with female-typical toys. Given the intertwining impacts of nature and nurture in human societies, can we learn anything from our animal relatives who grow up free from human societal norms?

In this post, I’d like to take a look at two recent studies that examine differing male and female toy preferences in primates.

Male Monkeys Prefer Trucks

First, in 2009 a research team led by Janice Hassett of the Yerkes National Primate Center at Emory University reported on experiments in which they the researchers to see whether rhesus monkeys (Macaca mulatta) would exhibit gender-specific toy preferences similar to those of human children.

In humans, studies have shown that boys gravitate strongly to stereotypically “masculine” toys such as trucks and other vehicles, while girls are less rigid, spending relatively equal amounts of time playing with boy-favored toys and with more traditionally “feminine” toys such as dolls. One hypothesis put forward to explain this difference has been that boys face greater societal discouragement when they play with “girl toys” than girls do in the reverse situation. The researchers figured that by looking at rhesus monkeys, who don’t face comparable social pressures to conform to gender roles, they might be able to illuminate biological influences on toy selection as well.

Of course I'm not playing; you gave me a Raggedy-Ann. Pass me that truck. Now. (photo credit: J.M.Garg, Wikipedia)

In their study, the researchers compared how 34 rhesus monkeys living in a single troop interacted with human toys categorized as either masculine or feminine. The “masculine” set consisted of wheeled toys preferred by human boys (e.g., a wagon, a truck, a car, and a construction vehicle); the “feminine” set was comprised of plush toys comparable to stuffed animals and dolls (e.g., a Raggedy-Ann™ doll, a koala bear hand puppet, an armadillo, a teddy bear, and a turtle). Individual monkeys were released into an outdoor area containing one wheeled toy and one plush toy, with the researchers taping all interactions using separate cameras for each toy, identifying all specific behaviors, and statistically analyzing the results.

The results closely paralleled those found in human children. As with human boys, male rhesus monkeys clearly preferred wheeled toys over plush toys, interacting significantly more frequently and for long durations with the wheeled toys. Also mirroring human behavior, female rhesus monkeys were less specialized, playing with both plush and wheeled toys and not exhibiting significant preferences for one type over the other. Here’s a chart illustrating the similar gender preferences of humans and rhesus monkeys (the information regarding human preferences comes from a 1992 study by Sheri Berenbaum and Melissa Hines):

The researchers noted that these similarities show that distinct male and female toy preferences can arise in the absence of socialization pressures and hypothesized that “there are hormonally organized preferences for specific activities that shape preference for toys that facilitate these activities.”

Barbie Really Is a Stick Figure

Next, in a brief paper published in 2010, Sonya Kahlenberg of Bates College and Richard Wrangham of Harvard University presented the first evidence of wild male and female primates, chimpanzees (Pan troglodytes) in the Kanyawara chimpanzee community of Kibale National Park, Uganda, interacting differently with play objects.

Over a 14 year period, Kahlenberg and Wrangham observed that juvenile Kanyawara chimpanzees tended to carry sticks in a manner suggestive of rudimentary doll play and that the behavior was more common in females than in males. Juvenile chimps, particularly females, would carry around small sticks for hours at time while they engaged in other daily activities such as eating, climbing, sleeping, resting and walking. While the same chimps used sticks as tools for specific purposes, the researchers were unable to discern any practical reason for the stick-carrying. The following chart shows the degree to which female chimps were more likely to engage the in stick carrying behavior:

Age and sex differences in the rate of stick-carrying in chimpanzees. Females: circles, solid line. Males: triangles, dashed line.

The researchers hypothesized that “sex differences in stick-carrying are related to a greater female interest in infant care, with stick-carrying being a form of play-mothering (i.e. carrying sticks like mother chimpanzees carrying infants).” In support of this proposition, they pointed to several factors. First, they never observed stick carrying by any female who had already given birth; that is, stick-carrying ceased with motherhood. Also, the chimps regularly carried sticks into day nests where they “were sometimes seen to play casually with the stick in a manner that evoked maternal play.” Finally, nurturing behavior towards objects like sticks had previously been reported in captive chimps and documented on a couple of occasions in the wild.

Also, the researchers suggested a social rather than biological basis for the behavior. Because regular stick-carrying hasn’t been reported in other wild chimpanzee communities, they proposed that that young Kanyawara chimpanzees may be learning the behavior from each other as a way of practicing for adult roles – a form of social tradition passed between juveniles previously described only in humans. Kahlenberg and Wrangham conclude by noting that:

Our findings suggest that a similar sex difference could have occurred in the human and pre-human lineage at least since our common ancestry with chimpanzees, well before direct socialization became an important influence.

So there you have it. One rhesus monkey study positing a biological and hormonal basis for gender-specific play, and another chimpanzee study emphasizing social learning… At least for now, the threads of nature and nurture impacting gender roles seem difficult to disentangle for non-humans, just as they are for us.

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ResearchBlogging.orgHassett, J., Siebert, E., & Wallen, K. (2008). Sex differences in rhesus monkey toy preferences parallel those of children Hormones and Behavior, 54 (3), 359-364 DOI: 10.1016/j.yhbeh.2008.03.008.

Berenbaum, S., & Hines, M. (1992). EARLY ANDROGENS ARE RELATED TO CHILDHOOD SEX-TYPED TOY PREFERENCES Psychological Science, 3 (3), 203-206 DOI: 10.1111/j.1467-9280.1992.tb00028.x.

Kahlenberg, S., & Wrangham, R. (2010). Sex differences in chimpanzees’ use of sticks as play objects resemble those of children Current Biology, 20 (24) DOI: 10.1016/j.cub.2010.11.024.

Peace on Earth, Good Will towards Baboons (and Humans)

In the middle of the 1980s, a catastrophic event shattered the lives of a troop of olive baboons (Papio anubis) living in the Masai Mara Reserve in Kenya. While the troop ultimately survived the experience, it emerged as a fundamentally transformed society with new cultural traditions. This is its story.

The troop, known as the Forest Troop, was initially very much like other olive baboon troops – that is to say, an extremely hierarchical and aggressive society, fraught with battles for dominance and bullying of subordinates. While a female will remain with her birth troop for life and automatically inherit her mother’s social ranking, a male reaching adolescence must set off on his own to find a new troop and then jockey with other males for position on the social ladder. The stakes are high, as baboon society is polygamous and dominant males enjoy the best access to mating and food resources.

And so it was. The Forest Troop lived in the woods and slept in trees about a kilometer from the open-air garbage pit of a nearby tourist lodge. Over time, many of its most aggressive males got into the habit of traveling to the garbage pit at dawn in order to scavenge for food, fighting for scraps with the males of a neighboring troop.

Then, in 1983, disaster struck. Spoiled meat that had been discarded in the garbage pit caused a fatal epidemic of bovine tuberculosis. Every single Forest Troop male who had foraged for food at the pit – 46% of the troop’s adult males – died in the outbreak. The remainder of the devastated troop, comprised solely of females and less aggressive males, survived.

In the wake of the outbreak, researchers who had been observing the Forest Troop noticed a dramatic reduction in certain types of aggressive behavior within the troop, not a particularly surprising observation given the loss of all of the most aggressive males in the troop. However, because the researchers wanted to focus on an intact troop that hadn’t experienced social disruption, they turned their attention away from the Forest Troop and shifted their efforts to studying a nearby troop that hadn’t been impacted by the outbreak.

A number of years later, though, the researchers returned to the Forest Troop and noticed something fascinating – even though there had been a complete changeover in the troop’s adult males, the troop’s less aggressive behavioral features had persisted. That is, a new generation of baboons in the Forest Troop appeared to be carrying on what amounted to a cultural tradition of lessened baboon aggression.

Geez, another housewarming party?! That Forest Troop has GOT to be some sort of a cult or something. (photo: Philippe_Boissel)

In order to analyze the changed behavior more rigorously, the researchers engaged in what’s known as a “focal sampling” process. They systematically recorded the social behavior of individual Forest Troop baboons from 1993 through 1996, and then compared those observations to two other data sets that served as controls – pre-outbreak observations they had made of the Forest Troop from 1979 to 1982, and mid-1990s observations of a different olive baboon troop.

What they found bore out their initial impressions. In particular, the new generation of Forest Troop baboons displayed patterns of dominance and aggression behavior that created less stress for low-ranking males. While the overall number of incidents involving aggression and dominance behavior was comparable to that seen in the control cases, the mix was different. Forest Troop confrontations were now significantly more likely to involve closely-ranked males, as opposed to the control group behavior pattern in which very high ranking males tended to pick on the lowest-ranking ones. This is notable, as confrontations between baboons with large power disparities typically reflect harassment rather than true competition and can be particularly stressful to the lower-ranking subordinates. Moreover, in the post-epidemic Forest Troop, males acted less aggressively towards females, engaged in more social grooming with females, sat in closer proximity to other baboons, and were more likely to have adult females, infants, adolescents, and juveniles as neighbors. Finally, the researchers found that subordinate baboons in the kinder and gentler Forest Troop had much lower levels of glucocorticoids, adrenal hormones secreted in response to stress, than did subordinates in the control groups.

C’mon, Dad, faster! Bumbo and Uncle Phil are waaaay ahead of us!

The researchers next considered how the peaceful new social traditions of the Forest Troop were being passed on to new males joining the troop: were troop members teaching the newcomers to be less aggressive, were new arrivals learning through observation or because they had more opportunities for friendly interactions, or was self-selection causing less aggressive males to gravitate toward this more peaceful troop? The researchers found that new males acted with typical aggression upon arriving at Forest Troop and were greeted with the usual belligerence from other males, but that the Forest Troop females were now uncharacteristically welcoming to the new arrivals, grooming them and otherwise treating them as established residents. Because the females didn’t seem to be engaged in active teaching behavior (they showed the same friendly behavior to even the most aggressive of the newcomers), the researchers concluded that the peaceful Forest Troop cultural traditions were most likely being passed on as newcomers observed more positive interactions with females and had more opportunities to relate non-aggressively themselves.

So, out of ashes of death, a baboon troop forged a new culture and found a way to maintain its peaceful traditions, passing them along to new generations. Makes one think….

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ResearchBlogging.orgSapolsky, R., & Share, L. (2004). A Pacific Culture among Wild Baboons: Its Emergence and Transmission PLoS Biology, 2 (4) DOI: 10.1371/journal.pbio.0020106.

Walk This Way! Experienced Female Elephants Show Their Naïve Younger Relatives How to Play the Mating Game

If you’re a female elephant, there’s a right way and a wrong way to play the mating game. To maximize your chances of reproductive success, it’s best to pair up with a dominant bull elephant in musth, a state of heightened arousal in which testosterone courses through the bull’s body, increasing both his sex drive and his aggression. A high-ranking musth elephant not only makes the fittest mate, but he can protect you by scaring off the less desirable younger males who would otherwise chase you around.

An experienced female knows this well, and plays the game accordingly. When she goes into heat – or oestrus – and attracts male suitors through chemicals in her urine, she gives impressive senior bulls the green light by holding her tail high, walking with an exaggerated gait, and exchanging affectionate trunk caresses. Lower-ranking young males don’t fare so well. She actively avoids them and, to the extent they aren’t chased off by her favored partner, she’ll often spurn their advances by running away. (Little known fact: female African elephants can typically outrun male ones.)

It’s not so easy for a young female entering oestrus for the first time. She sometimes runs from the larger musth males, who can weigh more than twice as much as her, and not infrequently ends up consorting with a series of younger, lesser males. This can lead to unfortunate results, especially when you consider that an elephant pregnancy lasts 22 months.

Now, though, there’s evidence that experienced females may help their younger relatives in sorting through the confusing tangle of elephant sexual dynamics. These helpful older elephants – sisters, aunts, mothers, and matriarchs – appear to simulate oestrus in order to show their innocent family members how to act, enabling them to avoid the pitfalls of poor mating choices.

If I said you had a beautiful trunk, would you hold it against me? (photo: WildlifeDirect, Dzanga Forest Elephants)

After hearing anecdotal accounts of this behavior, a team led by Lucy Bates of the University of St. Andrews decided to dig deeper by taking advantage of an invaluable resource – a comprehensive multi-decade database cataloging the daily life activities of 2,200 Amboseli elephants compiled by Cynthia Moss, Joyce Poole, and other researchers as part of the Amboseli Elephant Research Project (AERP).

Bates and her colleagues systematically combed through 28 years of detailed AERP records and located all occasions on which an observer had concluded that an identifiable elephant was in oestrus (based on postural and behavioral changes in females, interactions with males, etc.). In total, they found descriptions of 999 oestrus events, slightly less than 10% of which (98 events) recorded two or more members of the same elephant family displaying simultaneous oestrus behavior.

Next, the researchers cross-referenced these accounts with AERP demographic records to find any that must have been “false” oestrus events, which they defined as oestrus-like behavior by a female who was either already pregnant, in a state of lactation-induced infertility, or senescent (which they deemed to be the case if she was over 50 years old, had not given birth to any calves during the prior five years, and had no subsequent calves).

They discovered that, while false oestrus behavior was relatively rare (occurring only 19 times and representing only about 2% of all recorded oestrus events), its timing was fascinating. Very often, it occurred just when a young relative was coming into oestrus for the first time.

Even though simultaneous oestrus behavior had been recorded less than 10% of the time, over half of the false oestrus events (10/19) clearly occurred at the same time as the true oestrus of a young female family member who had never given birth. Further, subsequent birth records confirmed that on four additional occasions a false oestrus event occurred during the month that a young relative conceived her first calf (that is, the young female must have been in oestrus at the time, even though it wasn’t specifically called out in the AERP database). Finally, one of the false oestrus events occurred simultaneously with the genuine oestrus of a female relative who had given birth before. Thus, the large majority of the false oestrus events – 15 of 19 – coincided with true oestrus events, in most cases, the first oestrus of a young relative. (Moreover, note that the balance of the false oestrus events could also have coincided with true ones if, as in the four cases described above, the true oestrus event simply had not been observed or recorded in the AERP database.)

The researchers then examined various hypotheses that might explain the false oestrus behavior:

  • That false oestrus merely results from hormonal changes and has no functional purpose;
  • That it somehow induces sexual receptivity in the simulating female, thereby increasing her own chances of successfully reproducing;
  • That it indirectly benefits the simulating female by providing a young family member with increased access to suitable males (this type of indirect benefit is known as an inclusive fitness benefit); or
  • That it indirectly benefits the simulating female by encouraging a confused younger relative to engage in more suitable oestrus behavior (another potential example of inclusive fitness).

They quickly rejected the all but the final hypothesis. For one, hormonal changes couldn’t adequately explain either the observed patterns (false oestrus occurred in both pregnant and non-pregnant females, as well as during all stages of pregnancy) or the higher-than-expected coincidence of false oestrus with the genuine oestrus events of inexperienced relatives. Second, it was clear that the simulating elephants weren’t improving their own reproductive success: in 14 of 19 cases the simulating the female was already pregnant, and in four others she was senescent. Third, AERP records revealed that false oestrus behavior had no impact on the number of available males, the relative percentage of males who were in musth, or the amount of sexual activity engaged in by inexperienced female.

Ultimately, the researchers concluded that:

Further data is required to confirm or reject the hypothesis that this behaviour functions to teach the young, naïve females, but we suggest that it remains the only viable possibility based on the current analyses.

In particular, they noted that additional research and data collection was necessary to explain the instances in which false oestrus didn’t appear to coincide with an inexperienced relative’s oestrus as well as to support the notion that inexperienced females were able to correct substandard mating behavior after they were shown what to do by their older relatives.

In the meantime, though, you’d be well advised to stay away from those frivolous young guys and find yourself a dashing older bull who knows his way around the herd.

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ResearchBlogging.orgBates, L., Handford, R., Lee, P., Njiraini, N., Poole, J., Sayialel, K., Sayialel, S., Moss, C., & Byrne, R. (2010). Why Do African Elephants (Loxodonta africana) Simulate Oestrus? An Analysis of Longitudinal Data PLoS ONE, 5 (4) DOI: 10.1371/journal.pone.0010052.

An Uplifting Dolphin Story. Literally.

I’ve always found friendly interactions between animals of different species to be oddly reassuring. After all, the world can’t be all that bad a place if two animals, separated by differing genetic backgrounds and behavioral imperatives, can find a way to reach across the biological divide and share something, something joyful and positive.

Because of this, I’m an absolute sucker for all of those YouTube videos of cats curling up with mice, horses who befriend sheep, elephants and dogs who are inseparable, and the like. You know the ones I mean.

Many times, though, these are artificial pairings that spring up after we humans have altered the environment, habituating or even confining the animals with one another. While these human-influenced relationships can be incredibly heartwarming, it somehow seems even more magical when animals forge connections across species boundaries in the wild, in their native habitats and without any human intervention.

With that background, I’d like to introduce a paper published last year in the journal Aquatic Mammals1, which reports on two separate playful and – as you’ll see – uplifting encounters between bottlenose dolphins (Tursiops truncatus) and humpback whales (Megaptera novaeangliae).

The first took place on a January afternoon off the northwest coast of Kauai, when a group of eight bottlenose dolphins met up with a pair of humpback whales. Two of the dolphins – apparently adults – approached one of the whales, first appearing to surf the pressure wave created by the whale’s head as it swam, and later taking turns lying perpendicularly across the whale’s rostrum when it surfaced to breathe. Then, while one of the dolphins lay balanced over the end of its rostrum, the whale stopped and slowly lifted the dolphin high into the air. The dolphin maintained an arched position and made no effort to escape, allowing the whale to continue lifting until it was nearly vertical in the water, at which point the dolphin slid down the whale’s rostrum, dove into the water, and porpoised back to its fellow dolphins.

Here’s a color photo of the dolphin just about to go whale-sliding:

Look Ma, No Hands! (photo credit: L. Mazzuca)

And here’s a black and white series of shots that captures the full adventure sequence:

The second encounter also occurred on a January afternoon, this time off the northwest coast of Maui, when an adult female bottlenose dolphin swam up to a mother humpback whale and her calf. After diving underwater, the dolphin and mother whale resurfaced with the dolphin resting across the mother whale’s rostrum. The mother then proceeded to lift the dolphin a total of six times over 8.5 minutes, with the dolphin either lying on her stomach or right side during the lifts, which varied in length from four to 45 seconds. Again, the dolphin made no attempt to escape and held her position in such a way as to facilitate the whale’s lifting.

Here’s a sequence of photos showing this second duo demonstrating the proper technique for lifting a relaxed-looking dolphin:

The authors of the Aquatic Mammals paper considered alternate explanations for these interactions, including whether they represented an aggressive whale response to an antagonistic dolphin approach, whether the whales were demonstrating concern regarding perceived distress in the dolphins, or whether the cetaceans were simply playing together. They found the first two hypotheses to be unlikely – among other things, the interactions were too cooperative and relaxed in pace to be aggressive, and the dolphins were in good health and showed no evidence of distress. In the end, while the authors didn’t rule out the possibility that maternal instinct was involved in the whales’ lifting behavior, they concluded that the best explanation was that these were simply instances of interspecies play between the bottlenose dolphins and humpback whales.

Further, these bouts of play between dolphins and whales may not be all that uncommon, as back within the friendly confines of YouTube I was able to locate a video documenting another episode in which a bottlenose dolphin went for a ride on the rostrum of a humpback whale:

Play may serve a number of important purposes – for example, it may provide an avenue for intelligent, social animals like dolphins and whales to experiment with their surroundings, hone their physical skills and learn how to interact collaboratively with others. But aside from any practical evolutionary significance, I like to think of these encounters as illustrating how animals can, on occasion, take a few minutes away from the serious business of survival to share some pure joy and wonder with a fellow being, even a fellow being of a different species.

So, all of this is comforting. If dolphins and whales (and other animals who form interspecies bonds) can find a way to communicate playfulness with each other and to share experiences without any kind of a common language, perhaps we humans can do a bit better ourselves. Maybe some of the divides we see today – political discord, religious conflict, international posturing, cultural and racial inequities – aren’t so unbridgeable after all. Perhaps all we need to do is to remember an uplifting dolphin story or two.

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ResearchBlogging.org1Deakos, M., Branstetter, B., Mazzuca, L., Fertl, D., & Mobley, J. (2010). Two Unusual Interactions Between a Bottlenose Dolphin (Tursiops truncatus) and a Humpback Whale (Megaptera novaeangliae) in Hawaiian Waters Aquatic Mammals, 36 (2), 121-128 DOI: 10.1578/AM.36.2.2010.121.

Setting His Own Dinner Table: Spontaneous Tool Use by a Dingo

The name tags kept disappearing, and the staff at Melbourne’s Dingo Discovery and Research Centre was mystified. After romping around the grounds of the dingo sanctuary, Sterling, an 18 month old sub adult male, and his two canine companions spent time in an indoor enclosure that had a name tag posted on the outside of the steel mesh wall. The tag was positioned 1.7 meters above the ground, well out of dingo-reach. Still, it kept vanishing.

As reported in a paper published online last week in Behavioural Processes,1 the caretakers decided that it was time solve the mystery. First, they hung a small plastic envelope filled with food near the name tag and watched to see what the dingoes would do. The dingoes were having none of that, however – as long as observers were around, the dingoes studiously ignored both the name tag and the envelope of food. Since the direct approach clearly wouldn’t work, the staff resorted to sneakiness, rigging up a video camera and then leaving the dingoes to their own devices.

Success! When the staff returned to the enclosure, they found that the food was gone and, more importantly, that the videotape reflected perhaps the first documented instance of tool use by a member of the Canid family. As described in the Behavioural Processes paper:

Big deal, Lassie; when Timmy fell down *my* well, I hoisted him out using a system of pulleys. (Sterling at Dingo Discovery and Research Centre, photo by Dingo Lyn)

[A]fter several unsuccessful attempts at jumping for the envelope, Sterling “solved” the task by first moving and then jumping up onto a trestle table (1.2 m × 0.6 m × 0.73 m) which allowed him to gain the additional height necessary to reach the food item. To move the table, Sterling clamped his mouth onto the strut between the legs of the table. He then walked backwards, dragging the table approximately 2 m, until it appeared that either his back leg or tail touched the enclosure mesh. He then jumped onto the table, but as he was still at least a body-length away from the envelope, he had to span the gap between the table and the enclosure mesh by propping his front paws onto the mesh gradually moving them towards the envelope. At full stretch, he reached the envelope on his second attempt.

While this account of Sterling’s actions may sound impressive, it’s even more striking when seen on video:

Bradley Smith of the University of South Australia and his colleagues noted in their paper that Sterling’s behavior appeared to be spontaneous – he had never been trained or encouraged to position the table in order to reach food (or name tags) – but they cautioned that they had to rely on information provided by the sanctuary’s staff regarding Sterling’s (lack of) relevant training in the past.

No problem, just bring me a socket wrench, a crow bar and three sticks of gum... (Sterling at Dingo Discovery and Research Centre, photo by Dingo Lyn)

Sterling, for his part, was no one-hit wonder. According to sanctuary staff, from an early age Sterling was adept at manipulating his environment to serve his purposes. For example, during one breeding season he used his front paws to roll a barrel to a wall, jumped up on the barrel, scrambled over the wall, and approached a female dingo in another area of the sanctuary. Also, the staff and research team later videotaped separate occasions in which Sterling used his mouth to drag a plastic dog kennel to differing locations around his enclosure, allowing him to stand on the kennel and peer over walls into neighboring dingo enclosures.

Thus, while the researchers couldn’t exclude the possibility that Sterling’s problem-solving abilities were the result of observational learning or that they had somehow been reinforced when he was younger, they rightly recognized that he appeared to be engaging in “high order behaviour” in using tools within his environment to solve complex problems. (Indeed, on the face of it, Sterling’s problem-solving is quite very reminiscent of Kandula the elephant’s insightful use of a box within his yard to solve an out-of-reach food challenge.)

So, now that you know what canines are capable of, please feel free to ask your dog Barkley when he’s going to get around to assembling that futon you bought at Ikea. No more excuses.

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ResearchBlogging.org1Smith, B., Appleby, R., & Litchfield, C. (2011). Spontaneous tool-use: An observation of a dingo (Canis dingo) using a table to access an out-of-reach food reward Behavioural Processes DOI: 10.1016/j.beproc.2011.11.004.

2As we’ve noted in previous posts (see, for example, the post on the poison rat and the tuskfish tool post), scientific authorities have defined the concept of “tool use” in various ways. In the Beck and Shumaker treatise discussed in the poison rat post, the authors describe a couple of anecdotal instances that may qualify as canid tool use under their broad definition, including an account of a wolf mother who used meat as a “baiting” and “enticing” tool to distract her young pup. Fox, M. (1971). Possible Examples of High-Order Behavior in Wolves Journal of Mammalogy, 52 (3) DOI: 10.2307/1378613.

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.

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