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University of Toronto professor Alison Fleming.Fernando Morales/The Globe and Mail

There is far more to mothering than giving birth. Just ask Alison Fleming. The University of Toronto Mississauga psychology professor has spent the past four decades researching the complex neurobiology and psychology involved in motherhood. Through her work, she has learned that while the hormonal changes associated with birthing help prepare females to take care of their young, maternal behaviours don't just come automatically; they develop over time.

"There's a lot of stuff that comes into play.… It's not like there's an instinct called mothering," Fleming says, noting that fathers also undergo hormonal changes when exposed to their babies, and that women who adopt become every bit as attached and attracted to their children as those who raise their own offspring. "I think it's just a matter of getting the experience and the interaction."

The numerous studies Fleming and her colleagues have conducted over the years have contributed to a greater understanding of why mothering matters, and have provided insight into what drives mothers to nurture their young. A mother's love, support and physical touch (or, in the absence of a mother, the simulation of sensitive parental care) are all critical to the offspring's healthy brain development and social and emotional development, she says. And the greater the exposure a mother has to her babies, the stronger her motivation becomes to care for them.

Nevertheless, Fleming says, there is no one way to mother. "I think there are many ways to get to the same end, and that's really a message that I think is important," she says.

Fleming began studying mothering as a student at Columbia University in the 1960s. Her undergraduate thesis work on the effects of mothering in mice prompted her to reflect on her own childhood. Fleming's mother was an economist at the United Nations at a time when such positions for women were rare. Because her mother's work required her to live in a separate city, Fleming and her sister were primarily cared for by nannies.

"I suddenly tried to understand all that," Fleming says. "So at the same time as I was thinking about the research and the science and the animals, I was also thinking about my own situation."

Fleming went on to study the neurobiology of parenting in animal models at the Institute of Animal Behavior at Rutgers University in New Jersey. Since those early days, she has conducted extensive research on the effects of mothering in rodents, and has found that the way the brains of rodent mothers respond to their newborns are not so different from that of human mothers. In rats, for instance, she says, the limbic system of the brain mediates mothers' emotional reactions, while the cortex mediates their attention to their offspring. New research using functional magnetic resonance imaging (fMRI) by Fleming's graduate student Kathleen Wonch and postdoctorate researcher Jennifer Barrett is revealing that many of these same systems are activated in the brains of human mothers when they are shown a photo of their baby.

"There's actually many more similarities than you might imagine," Fleming says.

She adds that the sense of smell, which most mammals use to recognize their young, also plays an important role in human mothers' attraction to their newborns.

"What you find is that new mothers are much more attracted to the odours of the baby … on day two [after] the birth than non-mothers," she says. "But how attracted they are depends on how much they've interacted with them, how much time they spent actually holding them." The explanation for this phenomenon is likely quite simple, Fleming suggests: "I think that people learn very rapidly about things that are important to them," she says, noting that for mothers, "the odour [of a baby] becomes associated with positive feelings. I think that's what happens; they become conditioned very rapidly."

Also like rat pups, human babies can benefit from the nurturing of others if they are separated from their own mothers. Fleming notes that rat pups raised in social isolation become inattentive, impulsive and engage in less mothering behaviour themselves. But researchers have been able to reduce these deficits in the rat pups by using a paintbrush to simulate a mother rat's licking. In human children, Fleming says, the brain development of those who are raised in foster care or who are adopted in their early years is much more similar to that of children reared by their own families, compared with children who are raised in institutionalized care.

As a mother of three and a grandmother of two, Fleming says she hopes to expand her research to examine the science of grandparenting next. While she says she cannot pinpoint any specific findings from her work that have influenced her own parenting, her research has underscored the importance of responding to a child's needs.

"It's made me aware that you should be available to your kids, you know? That being sensitive is important," she says. "I just love my kids to death and I also love my science. I love the science of mothering."