Experimental Methods for Understanding Babies

But why should you believe us instead of those benighted experts who thought babies couldn't really see? How can we say we actually do know what babies think? With the help of videotape, scientists have developed ingenious experimental techniques to ask babies what they know. One whole set of techniques has been designed to answer two simple questions: Do babies think that two things are the same or different? And if they think they're different, do they prefer one to the other? You can present babies with pairs of carefully controlled events and see whether they can differentiate between them and which they prefer to look at or listen to. For instance, you can show babies a picture of a human face and a picture of a complicated object, like a checkerboard. Then an observer. who doesn't know what the babies are looking at, records their eye movements. By analyzing the babies' eye movements, you can see which picture they looked at longer. You can take the same idea a bit further by getting babies to suck on pacifiers that turn on different video- or audiotapes and determining which tapes they are willing to do some work for. You can see. for instance, if they will keep a tape of their own mother's voice playing longer than a tape of a stranger's voice.

Finally, you can exploit the fact that babies, like the rest of us, get bored. If you show babies the same old same old over and over, they stop looking and listening. Change the tape to something new, and they perk up and take notice. Developmental scientists call this boredom "habituation." So, for instance, you can show a series of different happy faces, and the babies will gradually lose interest; they'll habituate. Show them a new happy face, and they hardly look any longer. But show them a sad face, and they start to stare again. This means that babies somehow know that the happy faces are the same and the sad face is different.

Using these sorts of techniques we can show that at birth. babies can discriminate human faces and voices from other sights and sounds, and that they prefer them. Within a few days after they're born, they recognize familiar faces, voices. and even smells and prefer them to unfamiliar ones (it even looks as if they recognize their mother's voice at birth based on the muted but still audible sounds they hear in the womb) They'll turn toward a familiar face or voice and even toward a pad that has been held close to their mother's skin and turn away from other faces, voices, and smells.

Methods for knowing what's going on in a babies brain when exposed to various stimuli.