Another problem, though, is that when language is really being used, the whole situation is messy. Early on, a parent or is interacting with the child. They are trying to do some activity together. Originally, the parent may use some words, which the child may or may not understand. There is also some pointing and holding of objects. Eventually, language comes to play more of a role in this process.

That means that really studying the development of the use of language requires looking not just at the words kids are using, but also the developing complexity of the interactions between children and the people around them.

In an interesting paper in the June 2014 issue of by Lauren Adamson, Roger Bakeman, Deborah Deckner, and Brooke Nelson looked at a group of children over several years to begin to map out how these interactions change over time.

They observed children interacting with their mothers starting at a year and a half old and continuing until they were about five and a half. It is worth recognizing up front that this kind of research is hard to do. Most researchers focus on tasks that can be done in one session that take an hour or less. For a group to follow up with the same children over a period of four years is a tremendous amount of work.

At each visit, the mother and child played a game together in which the experimenter played the role of the director of a play. The mother was supposed to be a supporting cast member, and the child was the “star” of the play. Then, the experimenter set up several scenes for the child to play, in which the parent had to help the child achieve some goal. Over time, the actions got more complicated as the child’s abilities grew.

For example, in one scene, the experimenter brought several objects into the room, put them in a cabinet, and left the room. The mother was then supposed to get her child to hide the objects in a different spot and then talk to the child about where the experimenter would think the objects would be when she got back to the room.

The researchers looked at video of these interactions to examine how the the nature of the interaction changed over time, as well as how language use entered into the interactions.

Some of the results are fairly obvious. For example, at a year and a half, the parent and child interact with each other a lot, but there is very little language being used. Mostly, the parent is directing the child’s actions and occasionally using some words. By the time the child is 3, though, language is deeply embedded in the interactions. Almost every action taken by either the parent or child is accompanied by words.

An interesting change over time is that at younger ages, the mothers are really directing the interaction. They are setting up a structure for how the task should be accomplished by moving objects around and asking leading questions. By the time the child is five, the interaction is much more balanced. The parent still leads, but the child is also injecting more suggestions and making more recommendations.

Another change over time is the type of things that language is being used to describe. At three, much of the language is focused on single objects and observable elements in the world. By the age of five, there is also a lot more discussion about relationships among objects and not just about the objects themselves.

One surprising aspect of the data is that at the age of 2 and a half, there is lot of variability between kids in how much language they are using when interacting with their mothers. Some children use language in nearly every interaction, while others look like the 18-month-olds, where very little language is being used. But, by the age of 3 and a half, just about every child is using language in all of their interactions with their mother.

That means that as soon as children learn to speak reasonably well, their interactions shift immediately to the use of language, because it is such an important tool for communicating.

A study like this is largely descriptive. It focuses on what happens at different points in a child’s life as they start to converse with other people. What is nice about this work is that it focuses both on the use of words and sentences, but also on the kinds of interactions that children are having with others. Ultimately, an understanding of how language develops is going to require connecting the use of language to the situations in which language is used.

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