January 21, 2006

dog appreciation

recently, the new york times and other media reported a study according to which dogs can be trained to sniff cancer - or rather certain chemical substances produced by tumors - in breath samples:

In the small world of people who train dogs to sniff cancer, a little-known Northern California clinic has made a big claim: that it has trained five dogs - three Labradors and two Portuguese water dogs - to detect lung cancer in the breath of cancer sufferers with 99 percent accuracy.

The study was based on well-established concepts. It has been known since the 80's that tumors exude tiny amounts of alkanes and benzene derivatives not found in healthy tissue.

Other researchers have shown that dogs, whose noses can pick up odors in the low parts-per-billion range, can be trained to detect skin cancers or react differently to dried urine from healthy people and those with bladder cancer, but never with such remarkable consistency. [...]

The clinic collected breath samples in plastic tubes filled with polypropylene wool from 55 people just after biopsies found lung cancer and from 31 patients with breast cancer, as well as from 83 healthy volunteers.

The tubes were numbered, and then placed in plastic boxes and presented to the dogs, five at a time. If the dog smelled cancer, it was supposed to sit.

For breath from lung cancer patients, Mr. McCulloch reported, the dogs correctly sat 564 times and incorrectly 10 times. (By adjusting for other factors, the researchers determined the accuracy rate at 99 percent.)

For the breath from healthy patients, they sat 4 times and did not sit 708 times.

Experts who read the study raised various objections: The smells of chemotherapy or smoking would be clues, they said. Or the healthy breath samples could have been collected in a different room on different days. Or the dogs could pick up subtle cues - like the tiny, unintentional movements of observers picked up by Clever Hans, the 19th-century "counting horse," as he neared a correct answer. But Mr. McCulloch said cancer patients who had begun chemotherapy were excluded, smokers were included in both groups and the breath samples were collected in the same rooms on the same days. The tubes were numbered elsewhere, he said, and the only assistant who knew which samples were cancerous was out of the room while the dogs were working. [new york times, 1/17/06]

fascinating stuff. it makes you appreciate the powerful nose of a dog. today the new york times has an editorial on the subject:

What the Nose Knows

How well do you know your dog? The answer is, not nearly as well as your dog knows you. Given the right incentives, humans can certainly be perceptive enough. But most dog lovers discover, sooner or later, that dogs have an alertness to the behavioral signs of their owners that humans rarely equal. And that's nothing. Scientists have recently discovered that dogs can distinguish, with almost unerring accuracy, between breath samples from people with lung cancer and from people without. The dogs have to be trained to do it, of course. But the fact that they can do it at all is remarkable. There aren't enough biscuits in the world to teach a human to smell at such an extraordinary level of subtlety.

This news will give pause to almost anyone who lives with a dog. Just what a dog "knows" is hard to say, because the human idea of "knowing" is so closely related to the ability to express what you know. Even trained cancer-sniffing dogs express their knowledge - their distinction between samples - only by sitting or not sitting. But this is what always happens. We tend to forget the extraordinary powers of the animals we live with simply because we live with them. We tend to humanize them, which means, if nothing else, that we tend to reduce them - in terms of their sensory powers - to our muddling level. We can barely take in the fact that when a dog comes up and sniffs us, it is really giving us a nasal M.R.I.

Not that this will change the dynamic of our relations with man's best friend. For a while - remembering the cancer-sniffing dogs - some of us will wonder when we see our pets cock their heads, "What are you looking at?" But time will pass, and humans will be humans, and we will forget, at our end of the leash, that the beast we are walking with may already know things about us that we will discover only too late.

a - non-verbal- tribute to dog noses can be found on flickr.

No comments: