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Do dogs know each other by sight?

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Not smell? At Scientific American blogs, animal behaviour researcher Julie Hecht asks,

Does a dog know, merely by sight, that an approaching being is a fellow dog? Before you answer, remember this: Canis familiaris is the least uniform species on the planet. Members of this species come in a wide range of body shapes and sizes from itty bitty teeny weeny to absolutely ginormos. Adult members of this species appear as tight little packages, huge weightlifters, lean ballerinas, elongated hotdogs and everything in between.

Of course the obvious response is, “How do humans manage it?”

The old canard about the gullible couple buying a chihuahua that turns out to be a yappy rat* is funny precisely because it is not likely to happen. If that were a likely fraud, it wouldn’t be a joke at all.

Hecht describes a test:

To find out if dogs could ID other dogs based on appearance alone, the researchers first had to create a common language with their dog subjects. They did this with the help of three training sessions where dogs received a treat only when they approached the screen that had a picture of a dog’s face. Importantly, the same dog picture was used throughout the training sessions. During the training phase, the other screen was either all black, all blue, or had a picture of a cow’s face. The dog subjects were not rewarded if they approached any of the other non-dog pictures. This created a common language: “You are rewarded for approaching this ‘dog’ image, nothing else.”

We hope the treat was porterhouse steak because, with varying degrees of success …

The dogs prevailed! The nine subjects successfully identified “dog” from “non-dog” faces. More.

The researchers hope next to discover how dogs know each other only by sight.

Note: Snopes traces the story to the US, early 1980s and draws moral lessons about immigration. But I recall the legend clearly from Canada in the 1960s. At the time it seemed to descend from legends about people buying a piglet unseen in a sack—and it turns out to be a tomcat who runs away and climbs a tree.

It is likely a millennial (possibly perennial) joke, and maybe that aspect of the situation should be considered too: How do people really know, despite massive differences in canine appearance?

File:A small cup of coffee.JPG Is there a Platonic form “dog,” that survives the schemes of breeders?

See also: Furry, feathery, and finny animals speak their minds

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7 Replies to “Do dogs know each other by sight?

  1. 1
    mahuna says:

    I’m not sure how this will get scored with dogs, but in a similar study some decades back using chimps (gorillas?), the “trained” chimps would CONSISTENTLY sort pictures of monkeys and men correctly into 2 stacks, except they ALWAYS sorted pictures of themselves with the humans.

    I’ve never seen anyone explain WHY, but there is of course the chance that what the Testee was sorting was “animals who are not important” and “me and animals that give me food”.

    I would also note that I own/share my house with a Black Lab. Spencer can identify dogs (as opposed to squirrels, cats, deer, and most humans) from inside the house by what MUST be smell, since he doesn’t interrupt his lounging on the couch to stare out the windows looking for dogs. When we’re outside, Spencer will react to SOME, but not ALL, dogs at a distance of at least half a block if he feels they have intruded onto his turf (which exceeds the property lines for our lot).

    So the point of training a dog to recognize 1 or 2 repeated dog pictures from a single picture of a cow’s head doesn’t seem like much of a test. The test dogs might not even identify the “dog” picture as representing a real dog. And I’m pretty sure the poor dogs have no idea what the black and white cow’s head is.

  2. 2
    Jim Smith says:

    It looks to me like dogs can recognize “the most doglike face” from a pair of faces. That is not the same as understanding and recognizing that a certain animal is a dog.

    The dogs were trained to preform the task with a single picture of a dog before they were presented with previously unseen dogs and other animals in the experimental trials. That training picture, chosen by a human who already has an opinion of what a dog looks like, might influence the results.

  3. 3
    Jim Smith says:

    Above I wrote: “That training picture, chosen by a human who already has an opinion of what a dog looks like, might influence the results.”

    This is particularly true if the person who chose the training picture had already seen the pictures used in the experimental trials.

  4. 4
    Robert Byers says:

    For sure dogs and cats recognize people and creatures by sight. I can fool them with hats and glasses and changing body language. its not based on smell .
    Interesting that pictures do it. it seems to me they don’t recognize pictures because they need many dimensions to fill the thing out.
    I’m surprised at that.

  5. 5
    Jonas Crump says:

    It is an ingeniously designed experiment. It would be interesting to expand it to see whether they discern different species as humans are able to. And if so, do they tend to class them into similar categories.

  6. 6
    bFast says:

    Oi, you need science for this? My two dogs spend their days sitting on top of the couch watching out the front window. Every time a dog goes by, they go into a yapping frenzy. If it’s a fox, their behavior is quite different, much more aggressive. ‘Pretty sure they can’t smell a dog from 100 feet away through a triple-pain window.

  7. 7
    Virgil Cain says:

    Our dog recognizes the neighbor dogs by sight and even knows their names. She even remembers them years after they have moved or passed on.

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