"Do you go to school?" asks Dr. T. Berry Brazelton, author and chief of the development unit at Boston Children's Hospital, among other things.

"Yes," lies the 2-year-old, in perfect innocence, purloining part of the doctor's club sandwich. (Perfectly normal. See Brazelton's "Toddlers and Parents," Page 229, about how small children lie and steal.)

"I guess he wants to. It's the same thing," says Brazelton. (Wants to? You mean the child's desperate to go to school and this yearning's been ignored? You mean he's stifled and frustrated because he's not playing with finger paints? Is his mother doing something wrong?)

"Here, Mommy," says the subject, proffering a piece of mayonnaise-covered lettuce.

Dr. Brazelton pushes an ashtray forward. "You can put anything you don't want in here," he says kindly. Joe puts the lettuce in the ashtray and continues his scientific dissection of the sandwich.

Brazelton's sixth and latest book is "Working and Caring," advice for parents on combining a job and a family life. He was in Washington recently to testify on behalf of the Parental Leave and Disability Act, proposed legislation to require employers to grant a four-month unpaid leave for either parent to stay home with a newborn, newly adopted or seriously ill child. While here, he also opened the new, expanded facilities of the Regional Center for Infants and Young Children in Rockville. Then he moved on to a week of promoting his latest book. He also is an associate professor of pediatrics at Harvard Medical School, writes a regular column for Family Circle, is featured regularly on the cable television show "What Every Baby Knows" and runs a sought-after one-man pediatric practice in Cambridge, Mass. At 65, Dr. Brazelton is very, very busy.

"Brmmm, brmmm, brmmm," he says, down on his knees, pushing a small car. "Brmmm," says Joe. "MY car."

(The discomfiting implications of this interview are beginning to dawn. What if America's latest pediatric superstar sends me the message I'm a rotten mother? What if I'm like that awful Mrs. Stein in "Toddlers and Parents," who shrugged off her hyperactive son into the care of her 8-year-old, whom she bribed with cookies and candy, and who in turn sat all afternoon in front of the television set, getting fatter while the toddler bounced off the walls? And what about the Thomases in "To Listen to a Child," who allowed their infant daughter Lucy to drive them berserk, waking up every three hours for months and months?)

"He's a beautiful boy." That's what the doctor said. I have it on tape. "He's a beautiful boy."

It is largely thanks to Berry Brazelton that contemporary mothers and fathers worry about adequately "bonding" with their infants, hang things in their cribs for them to look at and have stopped worrying about thumb-sucking or teaching their kids to read by age 3. But aside from popularizing the knowledge that children are aware and learning from their earliest conscious moments, if not before, he has helped combine the fields of pediatrics and psychiatry, both by training doctors and by enlightening parents.

And he's seen them all. Yuppies, single mothers, working parents, older parents, single fathers, working-class parents, overachieving parents, neglectful parents. And if there is one message he has for them all, it is: Relax -- you can do it if you know a few simple things.

"It's a question of empowerment," he said. "I don't like to tell people what to do -- they unconsciously sense a put-down . . . Parenting is made up of making mistakes and learning from them. You don't ruin children if you're well meaning and understand your baby."

"I need that bread," says Joe, pointing to the doctor's roll. Brazelton hands it over.

"He has the best of wisdom that you'd learn from women," said his daughter Christina, who, he said, influenced him to revise his 1969 classic "Infants and Mothers" to remove sex stereotyping and traces of male chauvinism. "It's the kind of stuff your grandmother would have told you. It's very down-to-earth and not all this theoretical garbage."

But, as Brazelton said, most parents are well meaning -- it's the understanding-the-baby part they have trouble with. Having grown up in small families in a transient, increasingly age-segregated society, few of today's parents, he said, have any experience with babies. Families reproduce in isolation far from the entanglements of cousins, aunts and grandmothers. In addition, years of research have yielded useful information about babies and children that even grandmother doesn't know.

Brazelton, like most experts today, believes the first months of a child's life form the foundation of its relationship with its parents, which in turn forms the key to a successful family life and a well-adjusted person. A mother, for example, who blames herself for the periods of unexplained crying most infants go through, may not develop the confidence to deal with other issues. A parent unprepared for a child to scream all day and wake up during the night just before learning to walk is more likely to go berserk. In other instances, failing to recognize the signs of a particularly sensitive infant who reacts unhappily to too many stimuli will lead to total frustration and disappointment on the part of the parent.

"In my 30 years of research I have learned to understand the child's contribution," Brazelton said. "It isn't just the parents making mistakes [that cause difficulties]."

"Here," says Joe, spitting out a lump of now soggy roll. "You want this?"

"You can put that in your throwaway plate," says Brazelton. "This is called your throwaway plate."

"I put it here," says Joe, placing it in my hand.

Brazelton developed a diagnostic test, the Brazelton Neonatal Behavioral Assessment Scale, which is used across the country to measure the maturity of an infant's nervous system. He uses it as well as a tool to thrill parents, by demonstrating with red balls and rattles and the human voice the extraordinary range of reactions and responses that even a tiny infant can have. (One of the examples is the famous tongue test, in which a baby will imitate, within hours of its birth, the parent or doctor sticking out his tongue.)

The theory is: An informed parent is a better parent.

Toward this end, Brazelton recently left Redbook magazine to write his column instead for Family Circle, which, he notes, has a circulation of 18 million "and more working-class readers." Redbook, he said, "was headed more toward yuppies and sex." But the relationship with Family Circle is not altogether smooth: "They want me to be more directive, telling people what and what not to do," he said. "I'm not comfortable with that."

In his books, Brazelton describes specific behavior and situations, then comments, all in a scrupulously nonjudgmental tone. His portraits of families are composites drawn from real people but not based on them, and they sound very accurate.

Mrs. Thompson attempted to reseat Susan and to interest her in her cup. She gave Susan the cup with a bit of milk in it. . . . Mrs. Thompson moved away to fix breakfast and Susan upturned the cup on her head . . . Mr. Thompson . . . began to help with her feeding, attempting to spoon egg into her. She accepted a few bites at first dutifully. As he offered the next bite, she closed her mouth firmly and shook her head back and forth, upending the spoonful of egg into his lap. Patiently he offered her more milk in her cup, holding it for her this time. This brought out a violent thrashing from her arms which splattered the cup and milk across the kitchen. At this point . . . Susan was placed on the floor to roam . . . As they tried to eat, Susan stood at their knees, smearing sticky hands on Mr. Thompson's business suit . . .

-- From "Toddlers and Parents"

Brazelton comments that "a child at this age [1 year] is caught between his desire for simple attention from his parents and his growing realization that this is not all he wants . . . Provoking his parents to anger or to more violent interaction proves a kind of exciting potential of which he is just becoming aware. Unless Susan's parents shut it off by a firm, definite reaction, the possibilities for exploration will keep her at it for quite a period."

A photographer is trying to curb Joe's further exploration of the sandwich by getting him to sit in Brazelton's lap.

"Do you want to sit in my lap?" asks Brazelton, cheerfully.

"Yes," says Joe, and plunks himself down in his mother's lap.

Brazelton operates his one-man pediatric practice in Cambridge out of the basement of a modest two-story house, furnished with an aquarium and mementos of his travels around the world. Prospective parents are told that he is often out of town, and that they will be referred to another doctor in case of an emergency. They don't seem to mind.

"Kids love him," said one parent, John Trustman, whose 14-month-old daughter is a Brazelton patient. "He remembers my daughter, when she had her last cold, even what she was wearing the last time she came.

"I remember when she was about 10 months old, I was very worried because she didn't clap, and all the other 9- and 10-month-old children we knew could clap. I told Dr. Brazelton I was worried about this, and he must have laughed for 15 minutes. He said he'd seen parents who were worried their kids didn't crawl soon enough, or walk soon enough, but he'd never seen one worried about clapping.

"He told me not to worry."

Christina Brazelton, 28, is the third of Brazelton's four children. One of her older sisters is a banker, one is a rock singer and her younger brother is in college and thinking about medical school. Although she declines the credit, Brazelton said Christina helped raise his consciousness about gender and class stereotyping.

"He was coming under fire -- rightly so -- for being dated in the way he referred to women," she said. "Little girls had dolls and little boys had cars and everyone was white and middle class . . . As a mother, I think it's a wonderful book ["Infants and Mothers"], but language is important."

Christina's comments resulted in this footnote to the introduction of the revised edition, published in 1983: "In the first edition I tended to call babies by the masculine pronoun and to speak mostly of mothers. This led the book into the posture of appearing to exclude fathers. That was furthest from my wishes. For I know how strong is the competition for a baby between two caring parents -- from my own experience. Times have changed and this revised edition attempts to reflect the more involved role of fathers and to acknowledge babies of both sexes."

Brazelton occasionally refers to his children in his books. In one book, for example, he writes about how his effort to institute "quality time" with his children -- by herding them all together to talk to him when he came home -- was a fiasco. Sometimes he writes, almost wistfully, that he wishes he had done something different in a particular instance.

"He didn't have a very easy time as a father," said Christina, who did not want to cite any specifics. "I think everything in his books is accurate except what he says about us. Some people are brilliant teachers, but that doesn't mean they can do it themselves."

When it comes to grandparenting, however, she gives him top marks. When she delivered her son in April, three months prematurely, her father was studying Eskimo babies in the far reaches of Alaska. Once notified, Brazelton immediately headed for home via dog sled and airplane, and went straight from the airport to the baby's incubator.

"I was incredibly touched," said Christina. "It was exactly what I wanted him to do. In the face of a life-or-death crisis he was wonderfully supportive and in control."

He helped Christina and her husband deal with the considerable trauma of having a premature child (see "On Becoming a Family," 1981), teaching them how to "bond" with a tiny infant in an incubator. But he is not their pediatrician.

"No way," she said. "That would be too close for a professional relationship."

She may occasionally ask his advice, however, such as when she was worried that her son wasn't eating enough. "He said, 'Why he's as fat as a pig,' " she said. "Big help."

The book "Working and Caring," as well as his support for the parental leave legislation, reflects Brazelton's belief that helping the working family is one of the most important issues facing contemporary society. In the book he describes with considerable perception the sometimes unbearable burdens of working mothers and fathers: the inadequate day-care centers, the days when the child is sick, the employers who force a woman to return to work within weeks of giving birth at the threat of losing her job.

"Something's got to be done. People are hurting too much all over the country," he said. "It is really the family we're fighting for in this country, not just the child. We're really in a very dangerous, I think sick, symptom of society."

The price, he continued, is the further deterioration of the family, children who grow up without the ability to make deep, caring relationships, more divorce, more reliance on welfare, more trauma.

Mothers who know they have to go back to work too soon after their baby's birth -- any time before four months is too soon, according to Brazelton -- are afraid to become too attached to the child, both in the womb and after birth. They are afraid to breast-feed, because the pain of leaving their infant is too great, he said. This subtle distance between mother and child reduces, in effect, the parent's ability to parent, and the child's ability to develop his potential.

Brazelton has seen in his practice and research that a premature rupture in the mother-infant relationship produces predictable sleeping problems for both and eating problems for the child, usually at the end of the first year.

"The mother plays right into it . . . Of course, when they come home at night they're going to hover over that baby, and rush right in if it cries during the night. She might not see the gentle outcroppings of autonomy in the second year, but just ride herd over them. Those are correctable symptoms, but to me they're symptoms of the pain that I see going on right now."

He favors a federally mandated parental leave of four months, recognizing that many people can't afford to take an unpaid leave of even that long. Ideally, he said, the United States would imitate other countries and provide a paid leave. He does not oppose day-care centers, recognizing that many parents have no alternative and that such centers can be better than an incompetent baby sitter, but he subscribes to the ratio of one adult for every three children. Flexitime, part-time job hours -- whatever helps, he supports.

More and more parents are turning to people like himself for help, Brazelton said. Help for specific problems, and also help in articulating their needs for the general public. There are not, he might have said, many mothers or fathers who have time to testify before a congressional subcommittee.

Meanwhile, he offers some advice for dealing with the most stressful time of day for the working family: the hour after everyone gets home.

"First of all, you can't let yourself get that tired. You can't work so hard that you don't have a damn thing left for the baby. When you get home, put everything else aside for at least an hour. Let nothing interfere with being with your children, nothing. Buy TV dinners and eat them for a while if you have to. Then after an hour, each of you can go your separate ways and do what you need to do. Otherwise, you'll get into deeper and deeper trouble."

Despite these gloomy concerns, he retains a boyish spirit and his fascination with the small folk. After 30 years of being spat on, he still delights in the gurgles and smiles of an infant, and would rather play with a child than sign autographs.

The photographer invites Joe to push the button on his camera, and Brazelton watches attentively. The camera goes off with a thrilling flash and a satisfying noise, and Joe looks quite pleased. "That was very smart, Joey!" Brazelton says. "That was exciting! You are so smart."

"SMART!" He said it: "SMART!" That's on tape, too.