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Nature provides plenty of reasons for parents to adore their newborns. The giant eyes, the adorable coos, the flawless skin.

But in the days following the birth of my son in May, it was his fresh, slightly sweet and immensely satisfying scent that did me in. At all hours of the morning, I would take long, greedy sniffs as I cradled him in the dark. I’ve already forgotten the sleep I lost, but I don’t think I will ever forget that smell.

But what, exactly, was I smelling?

It’s a question that proved surprisingly hard to answer. And there is a sizable group out there, a Web search revealed, who insist that new baby smell is merely a myth, the lingering effect of scented wipes or an olfactory hallucination brought on by sleep deprivation. I couldn’t buy that.

Now a study published in the journal Frontiers in Psychology confirms my beliefs, suggesting that baby smell is not only real, but acts as a kind of sensory compensation for mothers.

Researchers asked 30 women — 15 who had recently given birth, and 15 who had never given birth — to identify mystery scents while their brain activity was monitored. When given the smell of newborns taken from pajamas, the women all showed activity in the same dopamine pathways that light up after ingesting cocaine, enjoying food, or other reward-inducing behavior.

The reactions were observed in all the women, though they were stronger in the new mothers.

Johan Lundström, a biologist with the Monell Chemical Senses Center in Philadelphia and a study author, believes that women’s brains are hardwired this way to provide an evolutionary incentive. “We think that this is part of a mechanism to focus the mother’s attention toward the baby,” he said. “When you interact with the baby, you feel rewarded.” A similar process may apply to men as well, Dr. Lundström said, though he lacks the data to prove it.

Much of the earlier research in the area of smell and babies has focused on how infants react to their mother’s scent. It had been shown, for example, that babies are more likely to reach for a pad soaked with their mother’s breast odor than a clean pad, and that newborns undergoing painful procedures are calmed by exposure to their mother’s breast milk but not the milk of others. It’s not surprising, then, that hospital staff now often place an article of mom’s clothing in the incubator alongside preterm babies in the hopes that it will calm them.

But there’s research on new baby smell to be found, too. A 1984 study found that mothers who were given three hospital gowns to sniff guessed which one their child had worn 80 percent of the time, a finding confirmed by later studies.

A 2006 study found that mothers prefer the smell of their child’s feces to that of other children. Do with that what you will.

Still, nobody seems to know for sure what causes new baby smell. But like any body odor, it is probably a combination of factors.

“Odors are chemicals,” Dr. Lundström said, but “it’s really hard to establish which chemicals. In natural body odor, we have roughly 120, 130 individual chemical compounds, and they vary by individuals.”

Complicating matters is the fact that baby smell is so fleeting. By six weeks of age, it is typically gone.

One likely component is the vernix caseosa, the white, cheese-like substance that covers babies at birth, Dr. Lundström said. Hospital workers usually wash it off right after delivery, but traces can remain in the baby’s hair or the folds of the arms and legs and contribute to new baby smell as it breaks down.

Amniotic fluid, too, has a distinct smell that both mothers and fathers can recognize that could also be a source of new baby smell. In 1988, researchers asked 15 mothers and 12 fathers to determine which of two bottles of amniotic fluid belonged to their child. Twelve of the mothers and 11 of the fathers guessed correctly.

And maybe the fragrance industry knows something that scientists don’t. After all, they’re the ones pumping out lotions and powders that smell “baby fresh,” containing ingredients like white musk, vanilla and orange.

Interestingly, those ingredients vary by country. “If you look at baby products from Spain or France, they tend to have orange blossom as an ingredient, because that’s in the countryside and that’s fresh,” said Michelle Krell Kydd, a fragrance industry consultant and prominent flavor and fragrance blogger. “Americans,” on the other hand, “have a love affair with vanilla and powdery scents.”

With my son approaching 5 months of age, his new baby smell has long since faded. But I still love his scent, as fresh and satisfying – and addictive — as ever. Who knows? Maybe it’s the lotion.