Analyzing canine intelligence is not straightforward. Just as we can never be sure precisely what the inner world of canine emotion is really like, we will probably never be certain whether dogs think the same way that we do. Science has so far been unable to tell us how self-aware dogs are, much less whether they have anything like our conscious thoughts. This is not surprising, since neither scientists nor philosophers can agree about what the consciousness of humans consists of, let alone that of animals. However, it is possible to examine scientifically whether dogs can or cannot do various things and then to infer the kinds of thoughts they might have, bearing in mind that, as dogs, they may not have the same priorities that we (or other animals) have in the same situation.
I have a good reason for delving into dogs’ actual intellectual capabilities rather than assuming, as many owners and even some scientists seem to, that their abilities are simply marginally inferior to ours. If we overestimate their ability to reason, then we are led into the trap of making them accountable for their actions in situations where they are actually unaware of what they are doing. If a dog could really work out what his owner was thinking when she arrived home to find her shoe in tatters, then punishment for that “crime” would work: The dog would be able to reason that he was being punished for something he had done a while ago rather than for whatever he happened to be doing at the moment the key turned in the door. As soon as we start treating dogs like “little people” rather than like the dogs they are, our actions become incomprehensible or misleading. Indeed, our actions are of such importance to dogs (as confirmed by virtually every piece of research done on their cognitive abilities), they inevitably become confused and distressed when unable to understand us.
The simpler forms of learning both enable dogs to piece the world together and allow us to train them to behave the way we want them to. But dogs can also think for themselves: They don’t just have feelings about the world but also, in their own way, have knowledge about their physical environment and the other animals around them (including humans, of course).
The formal study of canine intelligence dates back to the earlytwentieth-century work of Edward Thorndike. Thorndike’s approach to studying how animals learn was different from Pavlov’s; he was more interested in how they solve problems. Many of his experiments involved placing animals, usually domestic dogs or young cats, into puzzle-boxes of his own devising. These could be opened from the inside when the animal performed some kind of action. As you can see in the puzzle-box illustration, the door was attached to a weight that would pull it out of the way once the dog had unlatched it. The latch could be one of the wooden toggles on either side of the door, which the dog could paw upright by pushing its foot through the gap between the slats. Or it could be a bolt at the top of the door, connected by a loop of rope hanging from the roof that the dog could pull on with its teeth. Or it could be a treadle in the middle of the floor, which the dog had to press with its paw in order to release the door.
Thorndike’s puzzle-box
Thorndike was interested in finding out how the dogs solved the problem of getting out of the box and also whether they subsequently remembered how they’d done it. At the time, many people believed that animals like cats and dogs were capable of considerable insight—that they could, as it were, sit down and think things out. Thorndike, however, believed that a much simpler explanation would suffice.
Thorndike considered the possibility that simple associative learning, coupled with the dog’s natural inquisitiveness, might actually explain such apparently intelligent behavior. He found that his dogs would initially scrabble around the puzzle-box until they blundered on the mechanism that would let them out. He then fed them, as a reward, and put them straight back into the box to see if they could now escape any faster. If the dogs had insight into what they’d done, they would have immediately returned to the lever or pedal that had previously let them out. But in fact the dogs rarely did this. However, after repeated sessions in the box, they took less and less time to escape and eventually did start going immediately to the releasing mechanism.
Largely on the basis of these experiments, Thorndike came up with the concept of trial-and-error learning. Animals faced with a problem to solve will try out a variety of tactics that they would normally use in such a situation (in this case, being trapped). When one of these tactics happens to work, it produces rewards (in this case, being let out and then fed). The next time they are in a similar situation they will be more likely to perform the action that got them out last time or more likely to focus on the area where they had been when the door had opened on previous occasions. Both are explainable by simple operant conditioning: Either repeat whatever action preceded the previous escape or go to the place where you were immediately before the door opened (or both). This behavior requires no insight—no problem-solving skills—on the part of the dog. Based on Thorndike’s experiments and others like them, scientists now believe that dogs have rather limited powers of reasoning, certainly inferior to those of chimpanzees (and even a few birds).
The point here is not that dogs are stupid but, rather, that their brand of intelligence differs from the primate model. Though Thorndike’s dogs showed little evidence of problem-solving skills, they did an excellent job of recalling the correct escape method. In fact, they retained this memory for several months, even without any further exposure to the puzzle-box. (Dogs’ retention of skills they have acquired is generally very good, but they find it much harder to remember for more than a few seconds things they have merely observed.)
Memories of events, as opposed to memories of their own actions, may not be of great value to canids—indeed, they may be confusing. Canids, especially foxes, are known to be capable of remembering where they buried food, for days or even weeks afterward. Since the ability to retrieve food in this way is clearly adaptive, it is believed that they evolved the ability to recall where they buried the food. Conversely, canids are often faced with the problem of what to do when the prey they are chasing disappears. This is not something that is useful for them to remember for very long, because prey is unlikely to remain in one place for more than a short time without leaving some other clue. If the prey isn’t where it vanished and its scent is fading fast, then it’s probably long gone—and better to move on to another hunting site than to hang around hoping that it’s stupid enough to return to the very place it had just been chased away from. Thus evolution seems not to have selected for retention of such information for more than a few seconds.
Dogs’ short-term memory has been investigated experimentally. Using a method called visual displacement, scientists have tested how long dogs can remember where something has disappeared.4 Initially each dog is taught that its favorite toy is hidden behind one of four identical boxes: It first watches the experimenter hiding the toy and is then allowed to retrieve it. Once it reliably goes to just the box it has seen the toy disappear behind and is no longer searching the boxes at random, the dog can be tested to see how long it remembers where the toy has been hidden. In this second phase of the experiment, a screen is placed between the dog and the boxes immediately after the toy has been hidden, so that the dog has to remember which box its toy is behind. Then when the screen is removed, it has to recall that memory in order to locate the correct box. If it can’t, then it will go back to searching the boxes at random. If the screen is kept in place for only a few seconds, most dogs will go straight to the correct box, showing that they are indeed capable of both memorizing and recalling the location, provided the interruption is only brief. However, just a thirty-second delay is enough to induce mistakes. (Although dogs make even more mistakes after a minute’s delay, they do not get significantly worse if the screen is left in place for four minutes, at which point many are still performing better than chance.) Subsequent experiments have shown that dogs are better at remembering where things have disappeared in relation to their own positions (“to my left”) than in relation to landmark
s (“under the box that has boxes on either side”). Overall, many dogs’ short-term memories of single items appear to be rather fallible, perhaps because they are much more interested in working out what people want them to do in the here-and-now than in recalling precisely what happened a few minutes ago. This is not to say, however, that they pay no attention to the more fixed features of their surroundings; if that were the case, they (or their evolutionary forebears) would quickly get lost.
Although most pet dogs don’t have to memorize the features of the environment where they live (because most of the time we humans decide where they can go and where they can’t), they nevertheless retain their wild ancestors’ ability to find their way around and can use it if they need to. Indeed, dogs have very good memories for places—as might be expected from the descendants of animals that roamed widely in search of food. They have a variety of cognitive methods at their disposal for this purpose, such as the ability to memorize landmarks, but also more complex skills such as constructing mental maps of how those landmarks are distributed. Landmark-learning doesn’t require a complex brain—it’s how many insects find their way around—but it is useful nonetheless and, indeed, an essential part of more complex skills. Just as humans do, dogs effortlessly and continuously memorize the features of their surroundings; unlike us, however, they rely heavily on what things smell like. We might recall turning left around a dark green shrub; a dog would remember that shrub as smelling of orange with grassy top-notes. Yet despite these differences, dogs continually store (and then, presumably, gradually forget) information about features of the environment that they’ve recently encountered.
The dog’s propensity for memorizing landmarks can actually impede training. Younger dogs are so good at learning locations that they often spontaneously memorize their surroundings as part of the set of cues that tells them to do something. For example, puppies taught the verbal command “sit” in a training class may forget it as soon as they get home—because, in addition to the command, they have spontaneously memorized some feature of the room where the class was held as the relevant cue and, when in different surroundings, don’t recognize the command.
Many dog trainers therefore repeat a training exercise in a variety of places in order to break such associations and isolate the intended cue—in this case, the verbal command alone.
Dogs, as the descendants of hunters that roamed far and wide in search of prey, ought to have more refined navigational abilities than simple landmark-learning—and, indeed, it’s been shown that they simultaneously construct maps inside their heads. The standard way of investigating mental maps is to see whether animals can work out shortcuts for themselves. In one experiment, animal psychologists examined the mapping abilities of half-grown German shepherd dogs by showing them two caches of food hidden in the undergrowth in a large overgrown field.5 (They chose young dogs because older dogs might already have learned something similar to the task they were about to test them with, and they wanted to investigate the dogs’ natural abilities.) Starting at point C, one of the experimenters walked the dog to the first cache at point A, walked back to C, and then walked to the second cache at point B. Each dog, still on-leash, was then allowed to take the experimenters wherever it wanted to go. If the dogs had been using landmarks to find the food, they should have retraced the paths they had already been taken on. But in fact they invariably took a shortcut. Often this was directly on the path from A to B, but not always; sometimes a dog went to B first and then used the shortcut in reverse to get back to A. This suggests that some dogs, perhaps especially young ones, may spontaneously look for new solutions to a problem once they’re comfortable that their first way of solving it works—and can then go back to that solution once they’re sure that the new method isn’t an improvement on the original one.
Bird’s-eye view of an experiment demonstrating dogs’ abilities to take shortcuts. Left: the dog was first led from C to A, where it was allowed to find hidden food, then back to C, then to and from B, where it also found food. Lines of sight between A, B and C were blocked by vegetation. Right: a typical track taken by the dog after release from C.
The fact that some dogs seem able to use mental maps more flexibly than others suggests that this ability approaches one limit of the dog’s cognitive abilities; specifically, older dogs as well as dogs that have been under stress for a long time seem to lose some of their ability to orientate themselves. In one experiment, my colleagues and I investigated spatial ability by allowing gundogs to search a square grid of sixteen buckets placed four feet apart. A few of the buckets always contained food, which the dogs were allowed to eat once they had found it, but most only smelled of food. (In this way, we prevented the dogs from finding the buckets containing food simply by their smell.)6 Once they’d had a single opportunity to search the buckets, it was possible for the dogs to make two different kinds of mistakes: On subsequent searches, they might either visit buckets where there had never been food or revisit buckets that they should have known they’d already emptied. In the second phase of the experiment we made the task harder, by releasing the dogs from the corner of the grid opposite from the one they were used to starting from: To succeed, they would then have to essentially turn their mental maps upside down in order to know which buckets contained food. The younger dogs learned the task quickly and made few mistakes, even when released from the “wrong” corner. By contrast, older dogs, and those whose hormones suggested they had been stressed for a long time, made the most mistakes; they were especially confused when the release point was changed, suggesting that some part of their spatial memory had become impaired.
As we would expect from their evolutionary past as wide-ranging hunters, dogs appear to memorize their surroundings continuously and effortlessly, and also to cross-reference different memories to construct mental “maps” that enable them to navigate efficiently. However, they are less skilled than we are at reorienting themselves when viewing familiar landmarks from an unexpected direction. The “maps” themselves are probably accurate enough; it’s the ability to think about the maps that they appear to lack.
When they’re finding their way around, dogs probably use their acute sense of smell in preference to relying on what things look like, as we do. Their memories, too, are probably based as much on odor as on visual appearance, or even more so: Dogs can remember a particular odor—say, that of a previous owner or a dog they’ve lived with before—for many years, possibly as many as ten.
Even scientists sometimes overlook the dog’s preference for focusing on smell and, consequently, think that they have demonstrated complex abilities in dogs that are more likely just evidence of how well dogs detect odors. In one experiment, dogs were outfitted in blindfolds and ear defenders and taken on a short walk. The dogs were nonetheless able to retrace their footsteps. The scientists took this to mean that the dogs had memorized each turn, left or right, and how many steps they’d taken in between, much as you or I might under these circumstances. But, crucially, the scientists who performed this research didn’t allow for the dog’s acute sense of smell. In short, they failed to account for the possibility that the dogs could have retraced their steps either by following the odor of their own footprints or by using olfactory “landmarks” that they’d memorized while their vision and hearing were blocked.
Another experiment that illustrates the dog’s ability to pick out subtle differences in smell—though, again, not designed for this purpose—is one involving a border collie called Rico, who had been trained to retrieve his toys based on their “names.” As far as the dog was concerned, these were probably not literally the names of the toys but just commands, one for each toy. (Thus in his mind “sock” was not an abstract label for a sock but actually meant “Fetch your sock.”) The experimenters laid out some of Rico’s own toys, adding one that they had brought with them, different from any of those in the apartment. When Rico’s owner then called out a word that Rico had never heard before, the
dog retrieved the novel object. Although the experimenters claimed that this was evidence for linguistic skills in Rico7 and therefore, by extrapolation, in dogs generally, a simpler explanation is that Rico retrieved the novel object based simply on the fact that he found it fascinating because it had a smell different from that of everything else in the apartment (having never been handled by his owner). In other words, he was able to categorize toys as “mine” and “not mine,” an interesting cognitive ability in itself; but apart from that, his behavior was explainable by simple associative learning.
In sum, dogs find their way around by a combination of abilities that overlap with, but are distinct from, our own. They have a good memory for locations and a capacity for integrating these memories into “maps” that they carry in their heads, so their intuitive skill at finding their way around is probably rather similar to ours. As in our species, old age and chronic stress impair these functions, eventually to the point that the dog may appear confused when it loses its usual terms of reference. However, the features on dogs’ cognitive “maps” are at least as likely to be olfactory as visual, whereas the representations of the environment that we carry in our heads are almost entirely visual.
Their ability to construct mental maps suggests that dogs understand how things are connected together in the physical world, but when tested experimentally this hypothesis has been found not to be true. Dogs’ intuitive understanding of the ways in which objects connect together—their “folk physics”—is quite different from ours; they remember connections between actions and consequences, but without necessarily understanding how those consequences come about. One of the standard ways that psychologists use to test the ability to comprehend physical connections is the means-end test. For dogs, this involves retrieving inaccessible food by pulling on a string. In the simplest form of the means-end test, one piece of food is attached by a single string to a wooden block. The food is made detectable but inaccessible (e.g., it is placed under a mesh cover), whereas the block is left accessible. Most dogs can learn by trial and error that pulling on the block results in release of the food from under the cover. A casual observer would conclude that the dog understood the reason it achieved what it did—specifically, that the food was connected to the block by the string. However, if the task is made a little less straightforward, dogs are soon flummoxed. If there are two strings that cross one another and only one has food on the end, then the dogs should, if they understood the connections involved, choose the one tied to the food. But they don’t. Some pull on the block nearest to the food. Others just give up and try to dig the food out from underneath the wire mesh. (Some find even one string a problem, if it goes under the mesh at an angle.)8 The implication is that, when dogs do learn to get the food, they do so through straightforward operant learning and not through understanding that the food and the string are physically connected together. What they learn seems to be simply this: Pulling on a wooden block near the smell of food produces food. Other “intelligent” animals such as monkeys, parrots, and crows perform much better at this task—but does this mean that dogs are stupid? More likely, the experiment in question is just not a suitable test of their intelligence. The canid’s hunting lifestyle does not require a detailed understanding of precisely how things work—unlike the more opportunistic foraging strategies of monkeys, parrots, and crows.
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