Parentese is a comparatively new term. It is essentially baby talk, although when developmental psychologists and linguists refer to baby talk they have traditionally (since the late 1970s) called it motherese. The problem with this is that mothers aren't the only ones to use motherese -- fathers use it too, as do grandparents, older siblings, and strangers on the street. Parentese is currently coming into fashion as the politically correct term for motherese, although this may be a transitional phase on the way to infantese or somesuch. Modern textbooks will mention the term parentese and explain why you should use it, but will use 'motherese' in the index.
You already know essentially what parentese is -- it's how adults speak to babies. There are certain aspects of this speech that appear in all languages, and appear to be hardwired into our brains. There are, of course, certain aspects of what you think of as baby talk that are not universal, being unique to you or your culture. The core characteristics that constitute parentese are:
- High pitch: Babies respond better to high-pitched voices, and we accommodate them. A lot of what we do in parentese is designed to keep the baby interested, as this helps them learn that language is interesting and important. In addition, infants can understand intonation and volume changes before they can understand semantic content, and parents take advantage of this, exaggerating pitch and volume changes in their speech. Mothers typically use a wider range of pitch than do fathers, although this may be due to the fact that mothers have a wider range in the high frequencies than do most fathers.
- Clear speech: In parentese the speech sounds are better articulated than in normal conversational speech. Speech is slowed down slightly, especially if the parent is normally a fast talker. Parents have fewer dysfluencies and use fewer hesitation noises when talking. Vowel sounds are held for a bit longer, and slight pauses occur after content words.
- Simple speech: As you might expect, we tend to use short utterances (an average 3-3.5 morphemes per utterance, as compared to ~8 with adults) and simple syntax when talking to babies. We also limit our vocabulary. This is important, as the baby is learning from us, and while vocabulary and syntax don't come along until later, the easier we make it the better. Parents tend to repeat themselves often, paraphrase, and limit subjects to the here-and-now, as babies have no understanding of anything even remotely abstract.
- Increased facial expression: This also helps keep the infant interested in communicating. Facial expressions are exaggerated, and are used more frequently than in adult conversations. Gestures, such as shaking your head and nodding, are also exaggerated.
- Increased eye contact: During adult speech, eye contact is only made occasionally, but when talking to infants the parent and child make eye contact the majority of the time. This is obviously only possible when the baby is interested in making eye contact, and if the baby looses interest the parent may continue the interaction regardless.
- Proper conversational format: When we talk to babies, we talk as if we were holding a conversation. We ask questions, we comment, and most importantly, we take turns. We pause after every comment we make, waiting for an answer, and if the baby fills this pause we become even more animated, to reinforce it. If the baby does not fill the pause, we wait for a response, and then go on. This teaches the baby how to hold a conversation. These skills are so important that we start teaching them before we expect the baby to speak, before they can even babble. An American parent will pause 0.6 seconds + the average length of the infants utterance + another 0.6 seconds before taking another conversational turn; 0.6 seconds is the standard pause in adult conversational speech. Whether or not the infant is capable of processing this level of detail, we treat them as if they are.
- Reinforcement of any sound: Parents jump on any sound the baby makes as a chance to start a 'conversation'. This reinforces that talking is important, and encourages more production on the part of the child. Parents will often jump on even vegetative functions (coughing, burping, sneezing) as an opportunity to start a conversation.
- Strong focus on communication: Babies do a lot of things, but not all are equally reinforced. Gestures aren't responded to as much as are sounds, burping isn't reinforced to as greatly as is babbling, and nonsense sounds are not reinforced as greatly as are word-like utterances. The expectations of the parents escalate as the child ages, so a 10-month-old is not reinforced for burping in the same way a four-month-old is.
- Reliance on routines: Parents like asking simple questions and saying "hi!" and "bye-bye!" a lot. We don't know if this is to help the baby know what to expect in a conversation, if perhaps these are used because greetings and questions require a response, allowing the parent to treat any noise as a conversation turn, or if it's something else entirely.
Babies do respond to parent's speech, learning quickly what sounds are used in the parent's language, learning to respond when parents start a conversation, and learning that talking is fun. But they don't learn from everything in their environment; leaving the TV or radio going will not teach your child anything. Infants learn when they are actively engaged in communication, and parentese is designed to engage them as much as possible. This brings us to what parentese is not; there are certain things that we do that are not part of parentese, and while these things are generally not harmful, and may in many cases be helpful, they are not part of the programming that nature has given to every human parent.
- Using made up words: There is nothing wrong with using words like 'horsie' or 'night-night', but these are not parentese. These are just a type of very specialized speech you learn as a child and pass on. It is worth mentioning that American parents use fewer nonsense words and use better grammar when talking to babies than many other cultures; while nonsense is not part of parentese, it is certainly common.
- Monologues: It's not uncommon for parents to talk to infants in much the same way as they might talk to themselves; narrations, monologues, and thinking out loud are not baby talk.
- Routine games: It is normal for parents to play games with their babies, such as This Little Piggy and other nursery rhymes. Routine games like This Little Piggy tend to have a definite end, little input from the infant, and will often end as soon as the baby looses attention. Parentese does not have a definite end, and continues even if the baby doesn't show active attention, but is designed to encourage as much input from the infant as possible. Peek-a-boo, on the other hand, being an interactive game, might be considered consistent with parentese.
- Proxemics: An important part of the pragmatics of speech is the understanding of personal space. Parentese completely ignores personal space, making it one of the only parts of communication that we do not start learning from birth.
Cultural variations abound, even in something as universal as parentese. In Asian cultures the pitch changes and exaggeration of speech are not as pronounced as they are in European and American cultures, although they are still present. Japanese parents will ask fewer questions, and American parents will ask lots yes/no questions. English speakers use the rising pitch in asking a question to help gain the infant's attention, but this pitch pattern is not used in all cultures. For example, in Thai a falling pitch pattern is used, while in Mayan a flat pitch may be used. The infant learns from the parent, and responds appropriately. In the Deaf community, pitch is not a factor in communication, but signs are still exaggerated, used more precisely, and slowed down, just as speech is in hearing cultures.
There are some cultures that do not use parentese, or use it only sparingly. The Kipsigis of Kenya in particular, do not use parentese. Instead, infants and children are expected to learn language by hearing the mother speak and imitating it. This does not seem to delay language development in any way, which gives rise to some doubt as to the universality of parentese. However, parentese has been found on every continent, including pre-Columbian societies in North and South America, isolated African societies, Asian cultures, European cultures, and Deaf communities around the world. It may be that parentese is 'universal' in the same way that religion is; it can be avoided or ignored, but it is the default setting built into human brains.
You will occasionally find parenting books giving advice on 'how to do parentese'. This is not really a bad thing, but unless you are on the autism spectrum, you only need one piece of advice: don't be embarrassed. You are supposed to talk like that, and it is good for your baby.