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exposed. Sensitivity was measured as the length, in centimeters, that the scent tube had to be withdrawn in order to create a detectable level of odor. Zwaardemaker’s device, of which several versions were available, was reliable enough to explore the basic phenomena of odor perception and was used in laboratory demonstrations in colleges across the country. Nevertheless, Elsberg’s results were soon written up in Time magazine and on the front page of the New York Times. In the latter, the headline read, “Brain Tumors Detected by Scent with Device Keener Than the X-ray; Neurologists Hail Dr. C. A. Elsberg’s Discovery as Epochal—Based on Accurate Measurement of Sense of Smell, Which Was Viewed as Impossible Heretofore.” According to the credulous report in the Times, “Dr. Elsberg succeeded for the first time in measuring what had hitherto been considered universally as unmeasurable. He established a definite ‘scent yardstick.’”

Having nine cubic centimeters of air rammed up one’s nose is no barrel of laughs. However, blast injection proved to be a popular technique: most scientists prefer tight experimental control, even when precision comes at the cost of realism. Eventually researchers grew skeptical about the Elsberg method. They found that blast volume mattered less than blast force—this undercut the use of volume as a measure of smell ability. Even more troublesome, blast force was irregular—it depended on how abruptly the experimenter released the pinchcock on the rubber tube. The enthusiasm for nostril-blasting ended in 1953 when a psychology professor at UCLA compared odor sensitivity measured by Elsberg’s method and by natural sniffing. Blasting produced unreliable data, while natural sniffing produced very reliable data. The results blew Elsberg out of the water. Blast injection was not the scent yardstick he claimed it was. As the syringes and hoses were packed away for good, another psychologist ruefully wondered whether “we might be better off today if Elsberg had never publicized his creation.”

Mr. Natural: Keep on Sniffing

The physical characteristics of a sniff are smell dependent. Confronted with a weak scent, we take larger and longer sniffs, and more of them. We take smaller, shorter, and fewer sniffs to a strong odor. Considering how essential sniffing is to smelling, one might think this behavior would be studied by many scientists. Yet the bulk of what we know about sniffing is largely thanks to the work of one person, the Australian psychologist David Laing. He pioneered the natural history of the sniff.

In a series of elaborate studies beginning in 1982, Laing established how the dynamics of sniffing relate to smell. He controlled what people smelled with an air-dilution olfactometer, a device that generated a stream of air with precisely controlled odor levels. He measured how they sniffed by means of an oxygen mask with a tiny airflow probe concealed in it.

Laing found that natural sniffing took place in an episode of three and a half sniffs on average; some people used fewer, some many more. A person’s sniff episodes have a characteristic pattern that is stable across different odors and tasks. Sniff patterns were so stable and individually distinctive that Laing found he could identify a person by airflow data alone. He went so far as to liken sniff patterns to fingerprints.

At the time of Laing’s work, I was beginning my first experiments on human odor perception at the Monell Chemical Senses Center in Philadelphia. My odor sources were plastic squeeze bottles with fliptop caps. I would sit behind a screen and hand one bottle at a time to my test subject, who would squeeze, sniff, and rate the odor. As I listened to the wheezing of the bottles, I realized each person had a typical sniffing style. I soon developed a private taxonomy of sniffers. There were the Delicates, who took tiny, barely audible sniffs. There were the Honkers—people who squeezed the hell out of the bottle and inhaled so forcefully I thought they might hurt themselves. I also observed different psychological profiles.