The Female Brain (18 page)

Researchers have found that if mothers, for whatever reason—too many children, financial pressures, or careers that don’t allow enough child-care time—cannot be good enough nurturers and are only weakly attached to their babies, they can negatively affect the trust and security circuits of their children. On top of that, females “inherit” their mothers’ maternal behavior, good or bad, then pass it on to their daughters and granddaughters. Although behavior itself can’t be passed on genetically, new research shows that nurturing capacity in mammals
is
passed on, in what scientists now call a nongenomic or “epigenetic”—meaning physically on top of the genes—type of inheritance. In Canada, psychologist Michael Meaney discovered that a female rat born to an attentive mother but raised by an inattentive mother behaves
not
like her genetic mother but like the mother who raised her. The brains of the rat pups actually change according to the amount of nurturing they receive. Female pups showed the largest changes in brain circuits, such as the hippocampus and amygdala, that use estrogen and oxytocin. These changes directly affect the female rats’ ability to nurture the next generation of pups. The mommy brain is built through architecture, not imitation. This inattentive mothering behavior can be passed on for three generations unless most of the beneficial changes in the environment happen before puberty.

This finding has huge implications even if only some of it holds true for humans: how well you mother your daughter will determine how well she mothers your grandchildren. For many of us, the thought of being just like our mothers may be downright alarming, but already researchers are finding corresponding ties in humans between levels of mother-daughter bonding and the quality of care and strength of maternal bonds in the succeeding generation. Scientists also speculate that high levels of stress created between the demands of the workplace and the demands of the household can decrease the quality—not to mention the quantity—of nurturing care mothers are able to give their kids. And of course this behavior can affect not only children but grandchildren as well.

Scientists have also shown that high nurturing—from any loving, trust-inducing adult—may make babies smarter, healthier, and better able to deal with stress. These are qualities they will carry throughout their lives and into the lives of their own children. Children with less maternal care, by contrast, end up more easily stressed, hyperreactive, inattentive, sick, and fearful as adults. Studies of the brain effects of high-nurturing human mothers versus low-nurturing human mothers are few and far between, but one study showed that college-age adults who had low maternal care in childhood showed hyperactive brain responses to stress on PET scans. Researchers found these adults released more of the stress hormone cortisol into their bloodstreams than did their peers who had high maternal care in childhood. Those who had received low maternal care displayed increased anxiety, and their brains were more vigilant and fearful. This may be why Veronica always felt more easily stressed at work and during relationship challenges, and why she contemplated becoming a mother with such panic.

I often hear vivid stories about patients’ grandmothers—about how they were able to be there for my patients who had an overwhelmed, busy, or depressed mothers. Veronica’s paternal grandmother made her feel special, even though her maternal grandmother was as emotionally distant as her mother was. Veronica started to cry as she told me how her father’s mother would drop preparations for a dinner party to color with her or to play dolls. Grandma made blueberry pancakes with warmed syrup and helped Veronica make her bed and clean her room. When there was a party to go to and Veronica needed clothes, this grandmother took her shopping and often let her buy dresses she loved but knew her mother would not have allowed.

If it happens often enough, this kind of special nurturing from any allomother—a substitute mom—can override the lack of nurturing from an overstressed mother. It’s enough to break the cycle of nonattentive mothering, allowing the girl to provide more attentive nurturing to her own children. Veronica’s paternal grandmother may have been the linchpin in creating generational change. Years later, when Veronica stopped by to introduce her new baby girl to me, it was clear that she had a loving bond with her daughter and had passed on not the negative example from her mother but the nurturing, trust-inducing one from her grandmother.

A
TTENTION
W
ORK
D
ISORDER

Nicole, the Berkeley-MBA mom, was struggling with similar concerns when she came to see me. She had become so attached to her baby that she was having a meltdown about returning to work. She had a great job with terrific benefits, a high salary, and lots of opportunities for advancement, and she and her husband had incurred enough expenses that they needed the two incomes. She had to go back to work, and even though she had trouble imagining leaving her daughter in a stranger’s hands, she unhappily did it.

Most mothers, on some level, feel torn between the pleasures, responsibilities, and pressures of children and their own need for financial or emotional resources. We know that the female brain responds to this conflict with increased stress, increased anxiety, and reduced brainpower for the mother’s work and her children. This situation puts both kids and mothers in deep crisis every day. Nicole came back to see me just after her son turned three. She said, “My life’s just not working anymore.” She told me that her son was having bone-chilling, time-stopping tantrums in the grocery store when she had just two hours to figure out what to do with him and unpack the groceries before she slogged off to work. And that when he was sick and her husband was gone, she’d found herself praying at midnight that his fever would break by daylight so he could go to preschool and she would make it to her breakfast meeting—she’d been out a lot that winter with his illnesses and her boss’s patience was wearing thin. There were also the endless stream of half days at school coming up, and she’d have to beg the nonworking mothers in her kid’s class to take care of him until she got off work. She wasn’t sure she or her son could take it anymore, but she couldn’t afford to quit her job.

So is the working mother damned? Well, maybe yes and maybe no. In fact, one solution to these modern problems may come from our primate ancestors. As a rule, primates, including humans, are fairly practical about their investment in mothering. For example, primates in the wild are very rarely full-time mothers. Many mother monkeys balance infant care with their essential “work” of foraging, feeding activities, and resting. They also pitch in when needed to care for offspring other than their own—this is called alloparenting. In fact, in times of plenty, other moms easily adopt and care for foster children, even those from other communities or species. Many mammals have this capacity to bond with, nurture, and care for the offspring of others. An intriguing study of hunting among women of the Agta Negrito of Luzon (the Philippines) underscores the functions of networks of female kin. Women’s hunting has largely been regarded as biologically impractical because hunting is assumed to be incompatible with the obligations of infant care. Specifically, hunting forays were thought to impair women’s abilities to nurse, care for, and carry children. However, studies of cultures in which the females do hunt suggest exceptions that prove the rule. Agta women participate actively in hunting precisely because others are available to assume child care responsibilities. When women were observed to hunt, they either brought nursing children with them or gave the children to their mothers or oldest female siblings for care.

Mothering isn’t necessarily a solo occupation by design in humans—or restricted to the birth mother in an urban environment either. From the child’s perspective, nurturing is nurturing, no matter which loving, security-inducing caregiver it comes from. Nicole was able to negotiate a more flexible schedule at work so that her son could attend preschool half days along with his friend who lived next door and the two mothers covered for each other.

I
DEAL
M
OMMY
B
RAIN
E
NVIRONMENT

One environmental factor that is essential for good mothering in any animal is predictability. It’s not about how many resources are available, it’s about how regularly they can be obtained. In one study, mother rhesus monkeys were set up with their youngsters in three different environments: one had plenty of food every day, one had scarce food every day, and the third had plenty of food on some days but scarce food on others. The amount of nurturing behavior mothers gave to their youngsters in these environments was recorded every hour on video. Youngsters in the best environment, with plenty of food, got the most responsive nurturing from their moms, while those in the environments with scarce but steady amounts of food got almost as much. But those from the unpredictable environment not only got the least amount of nurturing but received abusive and aggressive attacks from their moms. The mother and infant monkeys in the unpredictable environment had higher levels of stress hormones and lower levels of oxytocin than their peers in the other environments.

In an unpredictable human environment, mothers become fearful and timid, and babies show signs of depression. The youngsters cling to their moms and are much less interested in exploring and playing with others—traits that linger on into adolescence and adulthood. This study supports the commonsense notion that mothers can do their best in a predictable environment. According to the primatologist Sarah Hrdy, humans evolved as cooperative breeders in settings where mothers have always relied on allomaternal care from others. So whatever a mother does and others do to help her, inside or outside the home, to ensure the predictability and availability of resources—financial, emotional, and social—may ultimately secure her children’s future well-being.

L
IVING FOR
T
WO

I can remember how stunned I was to discover that my independent and self-sufficient lifestyle no longer worked after I had a child. My thinking had always been that I could organize it myself and do most of the mothering alone. Boy was I wrong. Since a mother’s brain has virtually expanded its definition of the self to include her child, the needs of the child will become a biological imperative for the mother, perhaps more compelling to her brain than her own needs. I could no longer schedule my life so neatly. I didn’t know how much help from others, besides my husband’s, I would need. Every new mother needs to understand the biological changes that are going to happen in her brain and then plan out her pregnancy and mothering dynamic in advance. This life challenge can stimulate your brain circuits to grow like no other. Setting up a predictable environment for work and for loving, security-inducing child care will be crucial. A mother’s emotional and mental development depends to a great extent on the context in which she mothers. Knowing that you will need extra support for yourself and some good allomothers for your child will be key to your success as a mother. If we can provide a reliable, secure environment for the mommy brain, we can stop the domino effect of stressed mothers and insecure, stressed children.

The changes that happen in the mommy brain are the most profound and permanent of a woman’s life. For as long as her child is living under her roof, her GPS system of brain circuits will be dedicated to tracking that beloved child. Long after the grown baby leaves the nest, the tracking device continues to work. Perhaps this is why so many mothers experience intense grief and panic when they lose day-to-day contact with the person their brain tells them is an extension of their own reality.

Developmental psychologists believe that the female brain’s extreme ability to connect through reading faces, interpreting tones of voice, and registering the nuances of emotion are traits that were selected evolutionarily from the time of the Stone Age. These traits make it possible for the female brain to pick up cues from nonverbal infants and anticipate their needs. The female brain will turn this extraordinary ability on all her relationships. If she’s married or partnered with a male brain, each will inhabit two different emotional realities. The more both know about the differences in the emotional realities of the male and female brains, the more hope we have of turning those partnerships into satisfying and supportive relationships and families. Just what the mommy brain needs to be at its best.

SIX

Emotion: The Feeling Brain

I
S THERE ANY
truth to the cultural stereotype that women are more emotionally sensitive than men? Or that a man wouldn’t know an emotion unless it hit him on the head? My husband said we didn’t need a separate chapter on emotions. I didn’t see how I could write this book without one. The explanation of our different mind-sets lies in the biology of our brains.