To see if people could accurately identify a person’s age through smell, Lundstrom and his colleagues asked 41 volunteers to wear a special T-shirt to bed for five nights, after bathing and washing their hair with unscented products.

Each of the unscented shirts contained underarm pads which, by the end of five days, were steeped in the volunteer’s body odor.

Pieces of the pads were then dropped into glass jars, which were grouped by age: Some jars contained scents of 20- to 30-year-olds, some the scents of 45- to 55-year-olds, and some the scents of 75- to 95-year-olds.

The researchers then rounded up another 41 volunteers and had them sniff the jars. The volunteers were then asked to guess the age group associated with the scent in each jar and to rate the intensity of each scent and its pleasantness.

The volunteers were pretty good at figuring out the ages -- better than would be predicted by chance. But they were even more accurate when they were simply asked to group together all the jars that smelled like old people. Which means that they could detect the old person smell the best.

Intriguingly, the volunteers scored old people’s odors highest for pleasantness and lowest for intensity.