Babies as young as 3 months old are able to distinguish between photos of adult male and female faces, says Paul C. Quinn, PhD, a professor of psychology at the University of Delaware, in Newark. His studies suggest that infants do favor one sex over the other -- namely, the gender of the person who's their primary caregiver, whether it's Mom or Dad. "What's interesting is that the preference for one gender over the other appears to be learned from experience -- it's not preprogrammed," says Dr. Quinn.
The fact is, everything about your baby is growing rapidly -- after all, by the 5-month mark, she will double her birth weight. You just notice her nails more. "You can't see the organs or the brain growing, but having to trim those little fingernails is a reassuring sign of good growth," says Margaret Hostetter, MD, chair of pediatrics at the Yale School of Medicine.
When your little one reaches 5 or 6 months, he should consistently respond to his name. Until then, it may seem like Junior perks up whenever you call him, but he's probably not really picking up on his name. "By 2 to 3 months, your baby is responding to your face and your voice -- not necessarily your words," says Dr. Hostetter. "Within the next few months, your baby will turn to your voice. By the middle of his first year, he'll be able to distinguish the syllables of his name, although he won't yet understand what it means."
We may never know for sure, says Parents advisor Jodi Mindell, PhD, associate director of the Sleep Center at Children's Hospital of Philadelphia. Dream researchers depend on study volunteers to tell them if, when, and what they dream -- and babies aren't quite up to the task. We do know, however, that adult dreaming occurs during REM (rapid eye movement) sleep, and that infants spend 50 percent of their snooze time in REM, which is almost twice as much time as adults spend. "It would be a logical assumption that babies do dream and that it has something to do with their brain development since they spend so much time in this stage of sleep," says Dr. Mindell. But it's hard to imagine the landscape of your baby's dream world since he doesn't have language or clear concepts of people and things. Chances are, he isn't having nightmares, though, since he probably doesn't grasp the meaning of fear yet. "We suspect bad dreams don't happen until kids are 2 or 3 and have a better notion of being afraid and an active imagination that can conjure up boogeymen," says Dr. Mindell.
Hiccups are caused when the diaphragm, the respiratory muscle at the base of the chest, gets irritated and spasms. Since a baby's stomach and torso are small, it doesn't take much to fill his tummy to the brim and push it up into the diaphragm. "We like to see kids get hiccups," says Parents advisor Mark Widome, MD, professor of pediatrics at Penn State Children's Hospital, in Hershey. "It means they're well fed."
Developmental psychologists are split over this question. Some claim that babies are born with the ability to feel and express four basic emotions -- including happiness -- and others argue that infants learn to identify and communicate different feelings only through experiences with other humans. But they all agree that your newborn doesn't get the punch line of your hilarious jokes. Is she even aware that she finds something you said or did funny? Probably not. But that doesn't make her giggles any less precious.
"When a baby laughs, it's a positive thing -- she's enjoying herself," says Dr. Widome. Your baby's first laugh, which typically trills out before she's 4 months, is a sign of socialization -- she's picking up on the sounds and expressions you make when the two of you are having fun.
A hundred years ago, psychologists described babies' brains as "a buzzing confusion," but today's experts are more charitable. The current consensus is that infants are thinking all the time, busy trying to make sense of the world around them from the moment they emerge from the womb. "Babies are little experimenters," says Sue Hespos, PhD, a cognitive psychologist at Northwestern University, in Evanston, Illinois. "They gather information about their environment and are phenomenal at picking up patterns." Researchers like Dr. Hespos study babies' thought processes by measuring how long they look at events unfolding before them. They have found that you can hold a baby's attention for a significantly longer period if you do something unexpected. For example, if you dangle a box by a string so that it magically "floats," as opposed to placing it on a shelf as you've done before, a baby is likely to be more engaged. "Babies aren't concerned with earth-shattering philosophical questions, but they are thinking a lot about how objects behave and interact," says Dr. Hespos.
Babies are born with sweat glands, and they perspire to bring their body temperature down when they get overheated, as adults do. Unlike adult sweat, however, baby perspiration isn't stinky. "The apocrine glands, which are linked to body odor and clustered in the underarm, nipple, and groin, don't turn on until puberty," explains Dee Anna Glaser, MD, vice chairman of the department of dermatology at Saint Louis University School of Medicine.
Don't worry, your little one isn't destined for a career as a ventriloquist. "Young babies automatically experiment with their voice box," explains Dr. Widome. "In adults, the vocal cords and lips are working together to form words, but a baby isn't following these rules." Babies don't yet have the motor skills to coordinate sound with lip movement. "Before 6 months, an American, Chinese, and French baby will all make the same spontaneous, universal sounds," says Dr. Widome. "After 6 months, imitation takes off, and babies from different countries will begin to move toward language-specific mouth movements and sounds."
We wish we could tell you that the fierce, amazing love you feel for your precious newborn was mutual from the start, but that wouldn't be entirely honest. The thing is, your baby does not have anything approximating the life experience and self-awareness you have, so by necessity this thing called "love" means something very different to each of you. Not only can you put your strong feelings into words, but you also go out of your way to show your baby how much you care -- picking him up when he's upset and feeding him when he's hungry. Your baby's tokens of affection are naturally more limited. "When a baby bonds to his parent, he can't clearly express it, but rest assured, you are the center of his universe," says Dr. Hostetter. "From very early on, your baby will turn his head when you speak even when there are several women chatting in the room." In addition to recognizing Mom's voice, babies can distinguish her unique smell and methods of soothing.
Copyright ? 2006. Reprinted with permission from the October 2006 issue of Parents magazine.