May 11, 2007 -- Stopping and smelling the roses is a luxury many take for granted.
In fact, distinguishing smells is so central to life, it's hard-wired in the brain before birth, according to Dr. Richard Doty, director of the University of Pennsylvania's Smell and Taste Center.
ABC's Diane Sawyer visited him to find out about the cutting-edge technology shedding light on what smells mean. Sawyer also had her own olfactory senses tested.
Scent affects people from the earliest stages of life. Even in the womb, babies can react to the smell of garlic. Newborns specifically identify and react to the smell of their own mother's skin.
"[In] the third trimester of pregnancy, the baby will actually be able to discern chemicals inside the amniotic fluid," Doty said.
But with age comes the loss of some of the 6 million to 10 million cells at the top of the nose that are sensitive to chemicals that create aroma. Extreme smell loss can signal a serious disease.
"Early stage Alzheimer's disease will exhibit considerable smell loss," Doty said. "And we think as the brain ages, some of those brain areas associated with smell are the areas that accumulate the damage of Alzheimer's disease."
Sniffing and Judging
There's an unexplored frontier about smell and human personality.
Dr. Alan Hirsch, founder of the Smell & Taste Treatment and Research Foundation in Chicago, said he had speculative evidence that people can influence the way others judge them by their scent.
For instance, he said, if you want to seem confident and successful in a room, smell like clear good soap because people associate cleanliness with money and success.
Wearing citrus and jasmine can make others wary, while cucumber and green apple give off a happy vibe.
Doty said there was also science that showed that smell helps with the practical problems in life. People can train themselves to associate smells with actions -- for example, lavender with being sleepy -- and thereby solve minor health problems without medicine.
Knowing how vital the sense of smell is to life, Sawyer sat down to have her nose tested. Doty gave her 40 highly calibrated scratch and sniff tests with different smells, from bananas to motor oil.
After that, he tested strong vs. faint smells and then tested each nostril separately to see which one was functioning best.
How did she fare? She got 38 out of the 40 scratch and sniff tests right.
"You're at the 80th percentile, so you're doing better than eight out of 10 women your age," Doty said. "So you have a good sense of smell."