Dr. Kauer is using knowledge of how dogs smell to build an artificial nose for detecting land mines, but so far his best effort is only a tenth as good as a trained dog, he said. Dr. Myers has shown that scent emanates from an object in a plume that swirls and eddies in a turbulent flow so that there are patches of dense odor and areas of faint odor. In working, a dog quickly scans back and forth with its nose, scanning those densities, until it comes to what it thinks is the source. That may not always be the object itself, Dr. Myers said. Rather, because of air flow, the source could be in an upper floor of a building or the opposite side of the room.
Skilled handlers confirm that their dogs have detected scents emanating from distant sources.
Yet it is also not uncommon for dogs encountering a room full of drugs or a bag loaded with, say, suspect mangoes to fail to alert their handlers. Although the reasons are unclear, the odor in those cases may be so overpowering and evenly distributed around the room that the detector dogs cannot pinpoint the source, Dr. Myers suggested, so they do nothing. Also, their noses can become saturated with particular odors and desensitized to them, he said. Then, the dog literally needs time to purge the odor-laden mucus from its nose. Dr. Myers said recent research suggested that two different dogs trained in the same way could respond to entirely different chemical components of an odor and that the components to which they respond could change over time.