Whatever cynic first suggested that an infant's crooked little grin was a gas spasm surely never was a parent. But until recently, it was a misconception that was given a good deal of credence.

Happily, there is a whole lot of scientific evidence around these days that strongly supports the thesis that a grin is a grin is a grin . . .

It's all about the scientific interaction that some people call "bonding" and others call "attachment." Whatever it is, the specialists are finding that both parents and child need quite a lot of it, especially in the earliest days of a baby's life.

Tonight at 11 on Channel 26, there is a gentle and sensitive exploration of the bonding process: what science knows about it, what parents know about it and how it can be helped along under sometimes trying circumstances.

The choice of Sada ("Family") Thompson as narrator of "Right From the Start," a one-hour special made under the auspices of Chicago's WTTW, is a felicitous one. Although she lends grace and warmth, it is almost icing on the cake. It is the expressive faces of the babies, one after another, that bonds the viewer to this particular program.

Since work in the '40s that suggested that monkeys separated from their mothers grew up apathetic and antisocial, behaviorists have been trying to determine if that strong emotional tie between mother and baby is "just nature's way to ensure species survival," or, as the program asks, "Are there other messages being sent?"

There is strong reason to believe that there are plenty of other messages.

Do you know when a baby can first see? Or hear?

Investigators researching "Start" asked this question at random to a number of parents of small children.

"Oh, a few weeks . . .a few months . . .six months," came the answers.

Nobody was even close. Within an hour, the infant can both see and hear. Of course, there may be some confusion of stimuli, but when the newborn baby grabs his father's finger--as one premature infant described in the program does--and clings to it for an hour and looks into his father's face, the very good likelihood is that the baby is seeing the father.

Extraordinary filmed experiments done in Boston by the pediatrician, Dr. T. Berry Brazelton, explore the interaction between mother and infant. With a split-screen video tape, the researchers watch a baby respond to a mother's cooing, chirping, loving noises until there is some overkill, at which point the baby turns his head away briefly, as if to integrate what has happened. Then he turns back to coo and smile back.

In one case, the mother is asked to keep her face without expression as she looks at the baby. The baby makes every effort possible to make her smile: going through his own repertoire of cute new-baby tricks, finally, in frustration, beginning to fuss, at which point the mother melts.

In the birthing trend away from the often septic home conditions of the 19th century to a hospital's sterility, there was a strong victory over childbed fever and other bacterial risks to mother and child, but in the process, the loving surroundings were sacrificed.

Now the pendulum is beginning to swing at least part way back. "Start" explores some of the options, as well as approaches, to making up bonding to premature babies, for example, who must be separated from parents for some time at the start.

There's a lot of fascinating information. But, especially, there are some really delicious babies.