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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The Honeybee Waggle Dance – Is it a Language?

The Dance

More than half a century ago, Karl von Frisch rocked the world of behavioral biology with his conclusion that the honeybees (Apis mellifera) can actually communicate the distance to and direction of valuable food sources through an elaborate “waggle dance.” In what later led to his receipt of the Nobel Prize in Physiology or Medicine, von Frisch determined that bees recruited by this dance used the information encoded in it to guide them directly to the remote location of the resource.

In the typical waggle dance, a foraging worker bee who has found by a rich food source returns to the hive, is greeted by other bees, and commences dancing on the vertical comb surface within the dark nest (in other species of bee, like Apis florea, the dance is performed on a horizontal surface in direct view of the sun and/or other landmarks). She dances in a figure-eight pattern, alternating “waggle runs,” during which she vigorously waggles her body from side to side in a pendulum motion at about 13 times per second as she moves forward in a straight line, with return phases in which she circles back to the approximate starting point of the previous waggle run, alternatingly between clockwise and counter-clockwise returns. Here’s a video of a bee doing the waggle dance:

As the video indicates, the honeybee’s dance encodes key information about the resource. For instance, as she performs waggle runs on the vertical comb surface, her average body angle with respect to gravity corresponds to the direction of the food source relative to the current position of the sun (the sun’s azimuth). Accordingly, if the food source lies in the exact direction of the sun, she will waggle straight upwards; if the food lies, say, 30 degrees to the right of the imaginary line to the sun, she will angle upwards 30 degrees to the right of vertical. Also, the duration of her waggling runs is directly linked to the flight distance from the hive to the food source, with (for many bee subspecies) every extra 75 milliseconds of waggling adding roughly another 100 meters to the distance. Further, the more attractive the destination, the longer and more vigorously she dances, and the more quickly she returns for the start of each waggle run. Depending on the richness of the food source, she may perform up to 100 waggle runs in a single dance.

Next week ... the Tango!

Cognitive Complexity

It seems, then, that honeybees have evolved an extraordinary complex form of symbolic communication about distant resources, one that is beyond the capabilities of virtually every other species except for humans. Not bad for an insect.

The cognitive tasks implicated by the waggle dance are not insignificant: the dancer must remember the location and characteristics of a specific site she has seen on her foraging trips, and translate this information into the appropriate dance characteristics. She must also remember and take into account the position of the sun, and update that position as the sun moves (the ability to compensate for the sun’s movement by memory has been documented by researchers observing dances over several hours of overcast weather, when there are no celestial cues to be seen). The observing bees must “read” the dance, translate their sensory input into a resource location, and then find the resource, navigating as necessary around hills, houses and other obstacles.

In fact, the feat is so stunning that von Frisch’s findings were initially met with significant skepticism and controversy.1 At this point, the controversy has essentially been settled, with scientists recognizing that there is compelling evidence that honeybees really do communicate and act on the information encoded in the waggle dance, even though uncertainty remains regarding exactly which signals (tactile, odor, vibrations, air flows, etc.) the observing bees use to translate the dance into actionable information regarding the resource location.2

Is the Waggle Dance a “Language”?

So, the waggle dance is an extremely complex communication system, but is it a language?

Eileen Crist, Associate Professor in Science and Technology in Society at Virginia Tech, makes a rather compelling case that the waggle dance embodies many of the attributes of a true language.3 After noting that the waggle dance is always performed in front of an audience and is clearly communicative in nature, she describes some of the principal features that support its being characterized as a language:

  1. Rule-Governed. If a communication system is to be considered linguistic in nature, it generally must be based on a set of rules that are structured and used with regularity. This is the case with the waggle dance: the dance is always performed in a designated place within the hive, it is never done unless an audience is present, and it always follows a standard template for conveying direction, distance, and desirability. While the general rule is that the waggle dance is to be used to inform other bees about sources of nectar, when the colony has a special requirement (e.g., locating water when the hive is overheating or finding a new home when part of the colony must relocate) then the rules dictate that the dance purpose switches to this pressing need. Also, the general rule is that foragers dance about rich, reliable and near resources, but in times of need the “dance threshold” for less desirable resources is lowered.
  2. Complexity. A key dimension of a true language is its complexity, as it is unlikely that a communication system based on just a few rules will qualify as a language. The bee dance rules are not only extremely intricate, but they are applied in a versatile and complex fashion to respond to differing environmental factors and hive requirements.
  3. Stability and Dynamism. A core feature of human language is that a relatively fixed and stable syntax enables the dynamic generation of an indefinite number of new sentences. Similarly, while the waggle dance always takes the same recognizable forms, it “accommodates different purposes, shifting circumstances, urgent needs, and unprecedented events; while structurally identical every time, it is also contextually flexible.”
  4. Symbolic. By itself, the symbolic nature of the waggle dance has led to its being called a language. The dance symbolically represents conditions existing in the real world, actually enabling human researchers to “read” the information encoded in the dance to find specific honeybee food sources and even to design experiments about honeybee foraging behavior.
  5. Performative. According to linguistic theory and as first articulated by John Austin, languages not only describe the world, they also include what he called “performative” utterances, which are used to carry out actions.4 Not only is the waggle dance symbolically descriptive, but it has performative force in the sense that it elicits action from the bees who watch it (as Crist notes, the performative nature of the waggle dance is implicit in the way in which scientists “routinely deploy a vocabulary of announcing, reporting, summoning, recruiting, soliciting, inviting, commanding, and guiding” in describing it).

James Gould, Professor of Ecology and Evolutionary Biology at Princeton University, summarized both the controversy over the issue and the nature of honeybee dance communication as follows:

Some of the resistance to the idea that honey bees possess a symbolic language seems to have arisen from a conviction that “lower” animals, and insects in particular, are too small and phylogenetically remote to be capable of “complex” behavior. There is perhaps a feeling of incongruity in that the honey bee language is symbolic and abstract, and, in terms of information capacity at least, second only to human language.5

Gould estimates that the waggle dance is capable of communicating at least 40 million unique messages (“sentences”), more than 10 times as many as any other animal except for man.6

Not surprisingly, not everyone agrees that the waggle dance constitutes a true language. For example, Stephen Anderson, Professor of Linguistics at Yale University, acknowledges that honeybee dance communication is elaborate and cognitively rich, but concludes that it is unlike human natural language in that, for example, it is genetically fixed rather than learned through environmental interactions, it lacks a syntax in which the order of the communicative elements (words or actions) impacts meaning, and there is a close correspondence between the structure of the dance signals and the nature information to be conveyed (e.g., orientation of the waggle run and the direction to the resource).7

Some bees are better at the dance than others...

To Bee or Not to Bee

In the end, there will probably always be debate and disagreement over whether the waggle dance is a true language. Clearly, the waggle dance and human language are vastly different communication systems, and how we label the waggle dance in human terms may be missing the point. From the honeybee standpoint, the dance serves its purposes and contains all of the communicative nuances that the bees need within their environment. Maybe, the real point is that we should sit back and appreciate the fact that the honeybee, a small insect with tiny brain, has been able to evolve a system of communications that is so sophisticated that it has challenged human linguists to wrestle with the question of what distinguishes a true language and whether human language is really so unique.

Anyhow, time to stop droning on and sign off!

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1See, e.g., Gould, J. (1975). Honey bee recruitment: the dance-language controversy Science, 189 (4204), 685-693 DOI: 10.1126/science.1154023.

2See, e.g., Landgraf, T., Rojas, R., Nguyen, H., Kriegel, F., & Stettin, K. (2011). Analysis of the Waggle Dance Motion of Honeybees for the Design of a Biomimetic Honeybee Robot PLoS ONE, 6 (8) DOI: 10.1371/journal.pone.0021354; Gil, M., & De Marco, R. (2010). Decoding information in the honeybee dance: revisiting the tactile hypothesis Animal Behaviour, 80 (5), 887-894 DOI: 10.1016/j.anbehav.2010.08.012.

3Crist, E. (2004). Can an Insect Speak?: The Case of the Honeybee Dance Language Social Studies of Science, 34 (1), 7-43 DOI: 10.1177/0306312704040611.

4Hymes, D. (1965). : How to Do Things with Words . John L. Austin. American Anthropologist, 67 (2), 587-588 DOI: 10.1525/aa.1965.67.2.02a00970.

5Gould, J. L. Ibid. at 692.

6Gould, J. L. Ibid. at note 37.

7Anderson, S. R. 2004. Doctor Dolittle’s delusion: Animals and the uniqueness of human language. New Haven, Conn.: Yale University Press. ISBN-13: 978-0300115253.

Pantomiming Primates

When considering language abilities in non-human animals, it pays to keep in mind that spoken words are not the only path to sophisticated communication. For example, while great apes like chimpanzees and orangutans may be limited in their ability to adapt their vocalizations to human speech, they are able to control their hand movements very well, and can engage in extremely expressive and effective gesturing behavior.

In a thought-provoking study first published online last year and now appearing in the August 23, 2011 issue of Biology Letters1, two Canadian researchers, Anne Russon of Glendon College and Kristin Andrews of York University, reported on their extensive review of data regarding instances in which orangutans in Borneo have used “pantomime” to communicate with their target audiences.

What part of "give me more food" don't you understand? (photo credit: Tom Low)

Russon and Andrews mined 20 years’ data that had been collected during systematic observational studies on the behavior of ex-captive orangutans as they underwent rehabilitation and were living free or semi-free lives in the forest. After reviewing original field notes and videos covering over 7,000 hours of observation, they identified 18 salient pantomime cases (14 addressed to humans and four to other orangutans) in which orangutans physically acted out messages in order to communicate specific goals.

In most of the cases, the orangutans used pantomime to provide additional or better information after an initial attempt at communication had failed – for example, by being more specific about an action, item or tool requested; by offering better tools for a requested task after a previous tool had been ignored; by pretending to be unable to perform a task after a request for help had been ignored; or by clarifying friendly intent after non-aggressive approaches had been refused.

A few specific examples will help to illustrate how the orangutans used pantomime to achieve specific communication goals:

  • An adolescent female named Siti, who had partially opened and eaten a coconut, handed it to a technician who in turn handed it back to her, gesturing to her that she should finish the job. She proceeded to briefly, weakly and ineffectively poke at the coconut (very much in contrast to her prior behavior), before handing it back to the technician. When he again refused to help her, she used a palm petiole (stalk) to chop at the coconut repeatedly, as one would with a machete. Russon and Andrews described their interpretation of the incident in the data supplement to their paper:

After [the technician’s] first refusal she faked inability to do the job herself; after the second refusal she elaborated her request by acting out what she wanted done, specifying what tool and target to use and how to use the tool.  She acted out the actions she wanted of her partner, which included a skill that was not in her own repertoire (machete use).  Given the complex conjunction of conditions and the specificity of her request, Siti’s pantomime must have been invented on the spot even if she was familiar with all constituent elements.

Fortunately, you can see this incident for yourself, as there’s a video of Siti and the coconut – enjoy!

  • After a three year old female named Kikan had hurt her foot on a sharp stone, a research assistant removed the stone and dripped latex from the stem of a fig leaf on the wound to help make it heal faster. After that, Kikan (who had previously not been particularly friendly with the assistant, hitting or trying to bite her when she passed by) approached the assistant in a friendly manner on a number of occasions, holding up her wounded foot for the assistant to see. On one specific occasion, Kikan picked up a leaf, pulled the assistant’s hand until she paid attention, and then acted out the leaf treatment the assistant had given to the foot. (This is not only interesting for its communication content, but it could be an indication of episodic-like memory (mental time travel), a topic that Felicity Muth recently discussed in some detail in two Scientific American blog posts, here and here).
  • An adult female named Unyuk played with forest assistant who pretended to give her a haircut with a Swiss Army Knife. While they played she noticed a backpack, an item regularly stolen by orangutans in hopes of finding food. Unyuk made no immediate move for the pack – instead she continued to act out her role in the haircutting game, grabbing the hair on top of her head and inviting the assistant to continue playing as she gradually moved sidewise and closer to the pack. Once she had a free path, she lunged and made a grab for the unattended pack. (This was one of seven pantomimes that the researchers labeled as deceptive, where the actor feigned an inability, an interest or an intent in order to obtain help, distract, or express friendly intent and facilitate reconciliation.)

Russon and Andrews believe that some of the pantomime cases contain attributes of natural language:

including compositionality (large meaningful units are composed of smaller meaningful units…), systematicity (the actions and entities pantomimed are meaningfully rearranged following predictable patterns…) and productivity (…unique creations of the moment). Thus, orangutans can communicate content with propositional structure and have the kind of cognitive capacities with constituent structure typically associated with linguistic capacities.

Although spontaneous pantomiming appears to be fairly rare among orangutans (again, a total of 18 examples were unearthed from 20 years’ of data), the underlying data came from studies that were not focused on communication, and the researchers believe that other studies may have missed similar pantomiming to the extent that they focused on the functional aspects of gestures rather than the significance of pantomime as a medium for communication.

In any event, the study offers an eye-opening lesson in how sophisticated – to the point of being linguistic – non-verbal communication can be. If nothing else, we should not be too overconfident if we ever have a chance to play charades against a team of orangutans.

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1Russon, A., & Andrews, K. (2010). Orangutan pantomime: elaborating the message Biology Letters, 7 (4), 627-630 DOI: 10.1098/rsbl.2010.0564.

Does Berlitz Offer a Course in Prairie Dog?

Yes, that’s right – before your next trip to Arizona you may need to learn another language if you really want to be able to communicate with the natives.

Prairie dog about to raise its hand in English class (photo credit: Northern Arizona University/Con Slobodchikoff)

Professor Con Slobodchikoff of Northern Arizona University has been studying Gunnison’s prairie dogs for the last three decades, and, as reported by BBC News1, believes that these social rodents have some very special language abilities. Slobodchikoff told the BBC:

Prairie dogs have the most complex natural language that has been decoded so far. They have words for different predators, they have descriptive words for describing the individual features of different predators, so it’s a pretty complex language that has a lot of elements.

According to the BBC article:

The researchers found that the prairie dogs are confronted by so many predators that they have evolved different “words” to describe them all.

These words are barks and sounds that contain different numbers of rhythmic chirps and frequency modulations.

Individual prairie dogs have different tonal qualities, just as human voices differ, but different rodents use the same words to describe the same predators, allowing the alarm call to be understood by the rest of the colony.

For example, a single bark may be attuned to say “tall, skinny coyote in distance, moving rapidly towards colony”.

National Public Radio (NPR)2 recently featured Slobodchikoff’s prairie dog research as well, providing additional color about how Slobodchikoff and his students hid near prairie dog villages, used microphones to record shrill prairie dog predator warning cries (“It sounds kind of like ‘chee chee chee chee,’ “ says Slobodchikoff), and then analyzed the sounds using computer programs to parse out the differing frequencies and overtone layers of the prairie dogs’ warnings made in response to humans, dogs, coyotes, hawks and other perceived threats.

The NPR article describes how, after Slobodchikoff noticed that there were variations in the calls used to identify individual humans, he decided to perform further tests to see how specific the prairie dogs were being in describing what they saw:

He had four (human) volunteers walk through a prairie dog village, and he dressed all the humans exactly the same — except for their shirts. Each volunteer walked through the community four times: once in a blue shirt, once in a yellow, once in green and once in gray.

He found, to his delight, that the calls broke down into groups based on the color of the volunteer’s shirt. “I was astounded,” says Slobodchikoff. But what astounded him even more, was that further analysis revealed that the calls also clustered based on other characteristics, like the height of the human. “Essentially they were saying, ‘Here comes the tall human in the blue,’ versus, ‘Here comes the short human in the yellow,’ “says Slobodchikoff.

Amazingly, it doesn’t stop there. Slobodchikoff’s next move was to see if prairie dogs could differentiate between abstract shapes. So he and his students built two wooden towers on each side of a prairie dog village. They then made cardboard cutouts of circles, squares and triangles and ran them out along a wire strung between the two towers, so the shapes sort of floated through the village about three feet from the ground. And the prairie dogs, Slobodchikoff found, were able to tell the difference between the triangle and the circle, but, alas, they made no mention of the difference between the square and the circle.

Prairie dog warning system: "One if by land, two if by sea" (photo credit: U.S. Fish & Wildlife Service)

As the BBC puts it, if Slobodchikoff’s conclusions are correct, it would mean that “the chattering rodents communicate in a more complex way than even monkeys or dolphins.”

Pretty impressive stuff.

What do you think, does prairie dog communication amount to speaking a “language”? Is human language unique in some fundamental sense, or is there a continuum between what the prairie dogs are telling each other and what we talk about among ourselves?

We will have future posts regarding animal communication and linguistic abilities, and further explore the nature of language.  Until next time, chee chee chee chee, and to all a good night!

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1BBC News, “Burrowing US prairie dogs use complex language,” February 2, 2010.

2NPR, “New Language Discovered: Prairiedogese,” January 20, 2011.

My Border Collie Is Smarter Than Your Honor Student

Or so the bumper sticker says.

On this Fourth of July, it seems appropriate to salute man’s best friend in a brief holiday post. Meet Chaser, a true canine linguistic champion.

Chaser understands more than 1,000 words, along with simple sentences. Her vocabulary includes the names of 1,022 objects, including 800 stuffed animals, 116 balls and 26 “Frisbees,” any of which she can fetch on command.

Chaser, resting after studying for the bar exam (photo credit: ABCNEWS.com)

In addition, if a new toy is placed among her playthings, she is able to retrieve it when given its unfamiliar name, inferring its identity by a process of exclusion. She also has been studying her verbs, demonstrating that she knows how to “find,” “nose” and “paw” each of her toys. I assume that next she will be working on her gerunds and finishing her mastery of the subjunctive mood.

Happy Fourth, Chaser!

You can read more about Chaser and see her in action in this ABC News1 story.

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1ABC News, “World’s Smartest Dog? Meet a Border Collie Whose Memory Astounds,” February 9, 2011.

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