Who said they are dumb?
RB
http://www.medindia.net/news/view_news_main.asp?x=6858
The cancer can be detected by dogs from the breath of the cancer patients.
As a part of the study, five household dogs were trained within a short 3-week period to detect lung or breast cancer by sniffing the breath of cancer participants...............
...........The results of the study showed that the dogs were able to detect breast and lung cancer with sensitivity and specificity between 88% and 97%. The high accuracy persisted even after results were adjusted to take into account whether the lung cancer patients were currently smokers. ..........