There's a story in the dog research community about a dog being tested for its limits of detection. Seemingly confirming the myth of supersensitive odor-detecting abilities of canines, this dog appeared to be able to detect the target even at infinite dilution of samples. It turns out this dog was responding to a change in air pressure whenever it was presented with a sample-and not to the target. Stories such as this reflect the difficulty of quantifying canine olfaction.
Dogs respond to stimuli other than what researchers think they are presenting.
Dogs are unable to speak and answer questions directly, and some methods that have been used to detect a dog's response to stimuli are subjective, relying on the experimenter's interpretation of sometimes subtle behavior. Researchers at the Institute for Biological Detection Systems, Auburn University, in Alabama, have developed psychophysical methods that allow objective and unambiguous communication with dogs during testing. They eliminate competing stimuli when testing the ability of a dog to detect an odor and they teach the dog to use levers to signal clearly their response to a stimulus. The chamber takes away visual and auditory distractions, leaving the dog to respond only to odor. The wooden chamber is big enough to comfortably accommodate fairly large dogs.