Are dogs able to recognize that two items belong in the same category based solely on the sameness of their color?
Chaser the Border collie, now famously known as the smartest dog in the world, has achieved “academic” heights previously presumed out of reach of the canine mind. Not only was John Pilley’s groundbreaking research with Chaser a game-changer in the specific areas of animal behavior he aimed to address, such as a dog’s ability to acquire language skills and properly interpret syntax. But because language comprehension is a definitive benchmark used to measure intelligence in human beings, Chaser’s achievements are fueling an entire paradigm shift — altering not only what we know, but in fact the very nature of our inquiry into further understanding. For ages, scientists have turned to non-human primates in pursuit of insight into human intelligence. However, the dog — once considered a useless study subject in this realm –is now of ultimate interest as a species whose convergent evolution with humans informs the development of both our species’ cognitive make-up as socially cooperative (“pack”) animals.Thanks to Chaser, Rico, and other dogs like them, the modern comparative framework puts a dog’s cognitive capacity being on par with that of a human toddler. With this in mind, researchers are simulating all kinds of cognitive psychology experiments that were originally conducted with children, now using dogs as study subjects in place of two or three year-old humans.
Many studies have established that obvious (i.e. easy to observe and stable in time) cues such as color and shape are used for categorization in infancy and early childhood (Nazzi & Gopnik, 2000). Therefore, using the resources I had at my disposal– namely a six month-old black lab puppy named Betty, among a few other “supplies” – I set out to watch a dog’s mind work with my own eyes. I designed an experiment that combined elements from a few studies I found fascinating, including John Pilley’s, to determine whether or not Betty could recognize color as a cue for categorization. I “informally” hypothesized that given enough time and practice, and a failsafe experimental model, it is likely that dogs could learn to identify two objects as belonging to the same category based solely on the sameness of their color. I reached my supposition based on the following information revealed by previous studies:
(A) Contrary to popular belief, dogs have and use color vision.
(B) Dogs are able to identify individual objects by given names or labels.
(C) Dogs are capable of recognizing objects whose names they have learned as independent from the commands with which the objects are associated.
(D) Dogs are able to understand that one word might apply to both an individual object, and a category within which that object belongs.
(E) Dogs respond to non-verbal communicative cues from humans, and infer their meaning.
(E-1) Dogs are able to translate two-dimensional representations of objects as commands to retrieve the three-dimensional objects they represent.
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My own study is a work in progress; it will require more time and trials to complete, which means I do not have conclusive data to report. Rather, I will compare my project to the studies on which I based my hypothesis and experimental design; and will share the (inconclusive) data I was able to glean from the work I did with Betty, which paints at least part of an emerging picture, if not an entirely polished piece.
EXPERIMENTAL DESIGN & SET-UP
Using a clicker and training treats, I rewarded Betty for indicating two different objects by the proper-noun names I had given them. For simplicity’s sake, I named a yellow plastic puzzle piece toy “Yellow”, and will refer to it herein as YO (yellow object); I named a blue rubber bone “Blue”, and will refer to it herein as BO (blue object). I first introduced (BO) by setting it on one of three equidistant “X”s I had drawn on a large piece of white cardboard, and said to Betty, “Where’s BLUE”? When Betty touched or nudged the object with her nose or paw, picked it up, or obviously gestured in its direction by staring at it, I clicked and rewarded the behavior. Then we did the same with the yellow object (YO). Next, we repeated several trials during which both BO and YO were options. I made sure to move the items from one X to another randomly between trials, so that Betty was not simply conditioned to pick the object from one particular spot on the piece of cardboard.
I had then planned to introduce two variables into the experiment: First, I would interchange the blue rubber bone with a square pad of Post-It notes that was virtually the same shade of blue, (herein I will refer to it as bp for “blue paper”), and interchange the yellow plastic puzzle piece toy with a pad of Post-It notes that was virtually the same shade of yellow (herein referred to as yp for “yellow paper”). I would repeatedly present her with two items at once in one of three randomly-ordered contextual set-ups: Either (a) both original colored objects, or BO & YO, (b) both colored squares of paper, or bp & yp, or (c) one object and its oppositely-colored square of paper, or BO & yp/ bp & YO. *Had Betty chosen a colored pad of paper when presented with one as an option, she would’ve been choosing it by virtue of its color alone, as the colored pads of paper shared no other similarities with the original objects besides their color. They were different in texture, size, shape, and weight; and Betty wouldn’t have seen them before they were brought into the experimental context. [*We did a brief few trials using this set-up, which you’ll see at the very end of the video on YouTube. But we didn’t complete nearly enough trials to obtain significant results one way or another.]
Next, I would have the original blue and yellow objects set up on the X’s, as before. But this time I would hold up either the blue Post-Its or the yellow ones, and see if Betty would infer that by showing her the paper, I wanted her to select the object that was “the same” as the paper. I will go further into the implications of what this test would reveal shortly.
DOGS HAVE AND USE COLOR VISION
Dogs’ eyesight directly affects the efficiency with which they navigate the world around them. Consider the keen visual acuity it takes for a dog to hunt, or in fact become a vehicle of sight for a person who’s lacking it. While dogs’ visual prowess primarily lies in capturing fast-moving objects and/or those skittering across the landscape in low-light, studies have clearly documented that dogs possess and use color vision as well. Human eyes contain three types of color-receptive cones; therefore we are able to perceive a richer, more saturated, and wider color palette than dogs, whose eyes are equipped with only two classes of cone photopigment. In other words, humans have trichromatic vision, while dogs’ is dichromatic. The visible spectrum in dogs is divided into two hues: one in the violet and blue-violet range, which is presumably seen as blue by dogs, and one in the greenish-yellow, yellow and red range, which is probably seen by dogs as yellow (Miller and Murphy, 1995).
When designing my experiment, I had to be certain that Betty would not only be able to see the individual colored objects I was using, but also discriminate the two colors from one another. In other words, had I chosen objects that were green and yellow, there likely would not have been enough contrast for Betty to perceive a difference. Or had I chosen a red object and a green one, Betty would likely have only seen two shades of gray with little variation in between. I chose the colors I did because wavelengths at the two ends of the visible spectrum in dogs’ visible field – blue at one end and yellow at the other end – likely provide the most saturated and contrasted colors (Miller and Murphy, 1995).
In addition to merely having the anatomical capacity for color vision, studies show that dogs make use of the potential therein implied. Recent research out of the Royal Society has shown that dogs use chromaticity over brightness to glean information from colors in their environment. Scientists tested dogs’ preference when choosing test stimuli that differed in both hue and brightness. Incidentally, these researchers used yellow and blue for their experiment like I did, but they used two highly contrasted yellows, one bright and one dark, and did the same with dark and light blues. From their results, the team concluded that under natural photopic lighting conditions, color information may be predominant even for animals that possess only two spectral types of cone photoreceptors (Kasparson, et al. 2013).
WE KNOW THAT DOGS ARE ABLE TO LEARN OBJECTS BY NAME
Chaser the brilliant Border Collie ultimately learned to identify 1,038 objects by name over a three-year period. Assuming she and her person, John Pilley, trained 350 out of 365 days per year, approximately 4.5 hours per day, then one could assume they dedicated an average of 9.5 hours of training time to each object. Betty and I were able to dedicate approximately 1/5th of the necessary amount of time and practice it would take for us to achieve comparable results. After 100 trials of having Betty choose YO or BO, she was barely choosing correctly above chance, and seemed to be guessing for the most part about which object was which. When both objects were present, Betty chose correctly 56 times, and incorrectly 44 times. Had we had more time, and had she learned to identify each object in reliable “Chaser fashion”, our experiment would’ve moved beyond the theoretical and hypothetical stages. But alas, it did not. Betty’s age, breed, and level of previous generalized training must also be considered. Betty is a six month-old Labrador retriever in training to become a service dog for a child with autism. She is an intelligent dog, by my subjective account, but I wonder how the experiment might’ve gone differently if she were a Border Collie or Australian Shepherd, for example. I understand this is a variable in all canine cognition experiments that involve participants of only one breed, and especially for those involving only one participant. Had Betty had more time to practice identifying objects by name, I am sure we could’ve gotten to the “meat” of the color categorization hypothesis more quickly. As it stands, we have no conclusive results to report just yet, though we plan to continue working on it.
DOGS RECOGNIZE OBJECTS AS INDEPENDENT FROM THE COMMANDS WITH WHICH THEY ARE ASSOCIATED
Critics of the Rico language-learning study questioned whether or not Rico understood that the phrase “fetch sock” represented two independent morphemes – that objects are independent in meaning from the activity requested involving that object (Pilley and Reid, 2011). Pilley countered this criticism by conducting “Experiment 2” with Chaser, to determine whether Chaser treats the name of an object independent in meaning from the command given in reference to it (Pilley and Reid, 2011). Chaser was asked to act upon each of three named objects, “Lips”, “ABC” and “Lamb”, whose proper-noun names she had previously learned. While Chaser’s action of “taking”, “pawing”, or “nosing” an object when commanded to do so determined that she did, indeed, understand the action and object as independent from one another, what I did in my experiment with Betty indicated something altogether different, but still important and interesting.
I started out asking Betty to “get” (pick up in her mouth), “go get” (go a distance and pick up in her mouth), or “touch” (with nose or paw) either the blue object or the yellow object during the “learning the proper-noun name phase” of our experiment. I also used commands such as “drop blue”, or “give yellow”, while we were just “playing around” with the toys, so as to identify the objects by their given names as much as possible, thereby reinforcing the information in Betty’s mind. During this phase, I was impressed at Betty’s ability to discriminate between commands that required subtly different physical actions on her part – such as “touch” and “get” – especially when no context change occurred in between trials. That being said, after a while, for the sake of keeping it simple, I omitted the use of different action commands, and replaced them with just one word (or its conjunctive phrase): “WHERE’S or WHERE IS”. So I would say “Where’s blue?” or “Where’s yellow”. Interestingly, Betty would do one of five things when commanded only with “Where’s” or “Where is”. She would either (a) touch the item with her paw; (b) pick up the item with her mouth; (c) nudge the item with her nose; (d) nod her head quickly in the direction of the item; or (e) look obviously in the direction of the item, staring at it for a couple of seconds. To my mind, this implied that Betty was making an inference as to what I wanted from her. I had not previously used the command “Where is” in any other context, so she figured out on her own that all five of the aforementioned actions accomplished what I “implied” I wanted from her. She figured out that I wanted her to indicate, in one way or another, which object I was asking her about. I found this fascinating, especially in concert with all the other research findings that support social and cooperative learning in both species as related to our convergent evolutionary paths. This was yet another example of how dogs have evolved to read subtle human cues in novel situations, in which there has been no prior training or experience.
DOGS ARE ABLE TO UNDERSTAND THAT ONE WORD MIGHT APPLY TO BOTH AN INDIVIDUAL OBJECT AND A CATEGORY TO WHICH THAT OBJECT BELONGS
Another elemental criticism of the Rico study that John Pilley aimed to counter in his study with Chaser had to do with distinguishing between proper-noun names given to objects, and common nouns that represented categories. For instance, if Pilley had named a stuffed round object of Chaser’s “Ball” (let’s call the character “Ball Jones”), that would be distinctly different than him picking up a ball, and calling it “a ball”. In other words, Ball (Jones) with a capital “B” refers to an individual, named object, whereas “ball” with a small “b” refers to an item that represents a category of objects that fit the physical and functional description of what a ball is: it is spherical, it rolls, it bounces, etc. Pilley notes that categorization in animals has been widely studied in animal cognition in the last few decades, and a few studies have in fact demonstrated that dogs can form categories (Pilley and Reid, 2011).
Chaser learned the categories “ball”, “frisbee”, and “toy”. She could determine the sameness of balls and other balls, frisbees and other frisbees by their shapes; while she seemed to determine that toys – categorically – were items that served a particular function; that is, toys were things Chaser was allowed to play with. She even distinguished her toys from other objects that were similar in the house, but which were non-toys. For example, one of Chaser’s toys was a sock (let’s call him Sock McGillicutty, Sock for short), but then there were other socks in the house that were not for her to play with, and which she left alone, never confusing them with her toy sock.
In my experiment with Betty, I aimed to see if she would be able to categorize objects when the only likeness they shared was their color. In my experiment, I used the proper-noun names, Yellow with capital “Y” for the plastic puzzle piece and Blue with a capital “B” for the rubber bone. (For continuity’s sake, we could call these two characters “Yellow Johnson” and “Blue McGee”). In this case the categorical symbols were not common nouns, but rather adjectives. In other words, the yellow and blue post-it note pads represented the color categories (yellow with a small “y” and blue with a small “b”). Say I laid out the blue bone, “Blue”, and the yellow Post-It notepad, and asked Betty, “Where’s yellow?” In this case I would not be asking for “Yellow Johnson”, the proper-noun-named individual. Rather, I would be asking her to show me which item before her belonged in the category of “yellow things”.
Were Betty and I to have made it further into our experiment, we would have practiced generalizing and discriminating, as Pilley did with Chaser. I would’ve laid out several yellow objects, and several objects that were not yellow (and had no yellow in them), and asked Betty to bring me the yellow objects. Or, I would ask her to bring me a (pink object, for example), leaving one pink object in a group of yellow objects, to see if she could determine which one was pink based solely on the fact that it was not yellow.
DOGS RESPOND TO NON-VERBAL COMMUNICATIVE CUES FROM HUMANS, AND INFER THEIR MEANING
Dogs have been shown to infer from two-dimensional images that the experimenter wants them to choose an object that the two-dimensional image depicts. For this reason, I imagine Betty would/will be able to infer that when I hold up the yellow or blue Post-It notepads, I am asking her to choose the colored object whose color corresponds with whichever notepad I am holding up.
In 2009, the Dog cognition “dream team” at Cambridge University and Max-Planck Institute for Evolutionary Anthropology published a paper called Domestic Dogs Comprehend Human Communication With Iconic Signs. In it, the authors examined dogs’ ability to infer the communicative intentions of humans when given an abstract, non-verbal cue to fetch a referent object. In their paper, they point out that infants are able to make appropriate inferences and behavioral responses to adults’ communicative intentions (Kaminski et al., 2009). Evolutionarily speaking, this adaptation allows infants to benefit from adults’ guidance prior to the development of language comprehension. By the time a baby has reached two to three years old, he or she is able to infer from being shown a replica or photo of an object, that the adult showing the baby the icon wants for him or her to produce the real thing. Due to the emerging acceptance of a dog’s cognitive capacity being on par with that of a human toddler, it made sense for the dogs to have excelled at this particular test. That said, the notion that dogs are capable of handling the dual representation of an object that is both a replica of another object, and an object in its own right, is rather mind-boggling.
In this study, researchers investigated the skills of domestic dogs – some language-trained and some not – to make appropriate inferences and behavioral responses to human communicative intentions as expressed in their use of iconic signs, specifically physical replicas and photographs (Kaminski et al., 2009). Again, test subjects chosen for this study were Border Collies (one of them being Rico), who had overwhelming success with fetching objects when they were shown – in a “communicative context” either photographs of said objects, or smaller, physical replicas of them. The dogs even succeeded at choosing objects represented by the photographs, over identical copies of the photographs, when both were options. This further supports the truism that dogs infer meaning from what humans communicate to them, even when there is a level or more of abstraction involved.
This concept played a role in my experiment with Betty, however it translated differently than in the Kaminski study. When I interchanged the colored Post-It note pads with the plastic and rubber toys, and asked Betty, ”Where’s (Y)ellow/(y)ellow” (or (B)lue/(b)lue), I was asking her to interpret and understand the pad from three different perspectives: The (yellow) pad was an object in its own right (though unnamed and unfamiliar to her); it was a representation of the named item, “Yellow”; and by virtue of its color, it represented the category into which both it and its referent object (YO) belonged .
Had we reached the point in our experiment where I held up the Post-It pad silently suggesting that Betty show me its match, (and were Betty to have succeeded at this task), it would show what Kaminski’s study showed: that dogs’ skills in using human forms of communication are flexible as they generalize immediately to a new perceptual modality (vision vs. audition) (Kaminski, et al., 2009).
DOGS ARE ABLE TO CATEGORIZE ITEMS WITH OR WITHOUT HUMAN CUES
Friederike Range and his team at the University of Vienna, reasoned that “although domestic dogs are on the brink to become one of the model animals in animal psychology, their categorization abilities are unknown”, and that “this is probably largely due to the absence of an adequate method for testing dogs’ ability to discriminate between large sets of pictures in the absence of human cueing” (Range, et al. 2007). So, while Kaminski looked at dogs’ ability to draw conclusions about the task at hand based on non-verbal communication between the dogs and researchers, Range wanted to zero in on dogs’ ability to completecategorization tasks without outside help.
As of 2007, when this study was carried out, it was only one of two known categorization studies using dogs as subjects, the other being an acoustic stimuli categorization test to see whether or not dogs could discriminate dog from non-dog sounds. As was true for my experiment with Betty, the authors of this study had to fist take into account evidence for dogs’ ability to see in color. They determined – as did I – that although dogs have reduced color perception, they expected no severe physiological limitations of the dog’s ability to classify color (photographs), provided the category-specific aspects were not restricted to shades of red or very tiny fragments of the pictures (Range et al., 2007). Originally, I was using a third object in my experiment: along with the blue bone and yellow puzzle piece, I introduced a hot pink collar to Betty as well. I reasoned that, even if she saw the pink collar as a shade of gray, it would still be different enough from either the yellow or blue objects that she would put it in a category all its own. I later removed it though, because we weren’t progressing very quickly with two items, so I thought I would make it easier by eliminating a third.
The question most relevant to the Range study and my own, was if the dogs would be able to distinguish between category-relevant and category-irrelevant features (Range, et al., 2007). When I asked of Betty that she identify the yellow Post-It note pad as “(y)ellow”, after having been taught a plastic object with which the notepad shared one feature, its color, was called “(Y)ellow”, I was looking to see if she would practice a category-specific strategy. A category-specific strategy would require the subject to extract and combine the features common to most (or maybe even all) instances of a class and then react in the same way to all stimuli possessing those features (Cook et al., 1991). In other words, even though Betty had learned the plastic object by its name, “Yellow”, she would’ve also chosen the yellow notepad when I asked her to show me “yellow”.
All of the dogs in Range’s study eventually mastered the task of classifying photographs according to the presence or absence of dogs in them, and could transfer this practice to novel and even contradictory stimuli. Betty and I will need more time and practice before we can report on her ability to classify yellow or blue Post-Its as belonging to the same category as congruently-colored toy objects.
WE ARE THE SAME AND WE ARE NOT THE SAME
While achieving significant results showing that dogs’ cognitive capabilities are very similar to humans is exciting, results that disprove these types of hypotheses are just as valid and notable. While it is important to recognize similarities in human and canine minds, it is just as important to appreciate dogs and human beings, respectively, as unique and different beasts altogether. With results pending on my own experiment, the reality could go either way. Dogs may have and use color vision, and they may utilize it in ways similar to human beings when categorizing information in their environment. But then again, they may not.
A recent study on shape bias in dogs, for example, questioned whether or not dogs (in this case a five year-old Border collie named Gable) use an object’s shape to generalize it to objects in the same category. Using an experimental paradigm originally established to examine shape bias in children, researchers showed that when (Gable was) briefly familiarized with word-object mappings the dog did not generalize object names to object shape but he did to object size. Another experiment showed that when familiarized with a word-object mapping for a longer period of time the dog tended to generalize the word to objects with the same texture. These results show that the dog tested did not display human-like word comprehension, but word generalization and word reference development of a qualitatively different nature compared to humans (van der Zee et al., 2012). Again, results that illuminate the differences between the human mind and that of Caninekind are equally valuable to an overall understanding of who both we – and they – are.
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Father of Evolution Charles Darwin said, “The difference in mind between man and the higher animals, great as it is, certainly is one of degree and not of kind”. The nonhuman primate mind has long been considered the closest “in kind” to humans’. But today, dogs are ushering in a brand new era of cognitive exploration, leading us to look at animal behavior as related to social learning, cooperation, and communication between and among species. During the domestication process, dogs developed innate sensibilities to human emotional states, communicative cues, and comprehension of verbal language. The results of Chaser’s and other dogs’ studies are as much an existential statement on the meaning of intelligence – and the existential quandary of being – as they are a declaration of these particular animals’ beyond-impressive ability to learn, remember, and categorize objects. Rather than asking merely “how intelligent are dogs?”, Chaser, and other canine pioneers have us asking, How might various manifestations of canine and human intelligence have developed in the scope of our convergent evolution as interspecies partners? And, putting to good use what we’re learning from dogs in research settings we might ask, How can we use our findings to better communicate with the dogs in our lives whom we love so much, and seek so desperately to understand?
References
Pilley, J.W., Reid, A.K., (2011) Border collie comprehends object names as verbal referents. Behavioral Processes. doi: 10.1016/j.beproc.2010.11.007
Miller, P.E. and Murphy, C.J., Vision in Dogs. (1995) Journal of the American Veterinary Medical Association. Vol 207, No. 12, pp. 1623-1634.
Kasparson, A.A., Badridze, J. and Maximov, V.V., (2013) Colour cues proved to be more informative for dogs than brightness. Proceedings of the Royal Society B 280: 20131356.http://dx.doi.org/10.1098/rspb.2013.1356
Kaminski, J., Tempelmann, S., Call, J. and Tomasello, M. (2009) Domestic dogs comprehend human communication with iconic signs. Developmental Science. Vol 12, No 6, pp. 831-837. DOI: 10.1111/j. 1467-7687.2009.00815.x
Range, F., Aust, U., Steurer, M. and Huber, L. (2007) Visual categorization of natural stimuli by domestic dogs. Animal Cognition. DOI: 10.1007/s10071-007-0123-2
Van der Zee, E., Zulch, H. and Mills, D. (2012) Word Generalization by a Dog (Canis familiaris): Is Shape Important? PLoS ONE 7(11): e49382. DOI: 10.1371/journal.pone.oo49382
Nazzi, T. and Gopnik, A. (2001) Linguistic and cognitive abilities in infancy: when does language become a tool for categorization? Cognition. Vol 80. B11-B20
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