Dog Sense (33 page)

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.
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(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.)
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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 Rico
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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.)
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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.

Dogs do better in another aspect of “folk physics”: the ability to count. Because this ability is regarded as an indicator of intelligence, scientists have examined it in a wide variety of animals, including dogs. It's clear that dogs can tell the difference between a half-full bowl of biscuits and one that's a quarter full, but do they actually count the biscuits or just judge the size of the pile? Researchers have attempted to answer this question by using a technique first developed for the study of human infants.
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When babies as young as five months are shown one doll and then another, and then, after a brief gap, three dolls in the place where there logically ought to be two, they look at the three dolls for longer than expected—they seem surprised that the third doll has come from nowhere. Their reaction suggests that they had added together one doll plus one doll and were therefore expecting only two. It seems logical that dogs should also be able to do this: A mother dog who sees two of her puppies go momentarily out of sight should presumably be surprised (and get up to investigate) if, say, only one reappears.

In the means-end test, dogs usually pull on the string that's nearest to the food, not the one that's actually connected to it.

To test dogs' ability to count, the researchers in this study used food treats rather than dolls. The dogs were shown first one treat being placed in front of them and then a second. Next, a screen was placed between them and the treats. When the screen was removed and either one treat or three were revealed, they stared at the treats for a long time, as if in disbelief. If there were two, as there should have been, they just glanced at them only briefly.

Although rather few studies have been conducted on this topic, it seems that dogs have little intuitive grasp of how the world around them works. This was Thorndike's conclusion from his puzzle-box experiments, and one that has been confirmed by all of his subsequent experiments. Of course, dogs can easily learn how to manipulate some specific aspect of their surroundings in order to get what they want—but they appear not to understand why the manipulation works, just that it does.