Many parents lament their waning commitment to their child's baby book. When did she start saying that word? Who taught him to say that? When did she begin calling herself "I"? It's all a blur we wish we'd written down.
But for researchers who study the intricacies of how and when children acquire language, these milestones can be important predictors of future success or – more importantly – problems. And they are writing them down. This week, Canadian researchers found that the scores on a questionnaire administered to parents of toddlers and preschoolers can be linked to similar measurements taken once the children are attending school.
And at a Vancouver conference last week an American researcher, Leslie Rescorla, outlined the minimum 25 words two-year-olds should have under their belts, which included such words as cookie, milk and dog.
At the panel discussion where Prof. Rescorla shared her work, the moderator called the 25-word list the "canary in the coal mine," according to the New York Daily News. In fact, Prof. Rescorla, director of the Child Study Institute at Bryn Mawr College in Pennsylvania, has suggested that the normal range for a two-year-old is 75 to 225 words.
This and other work is aimed at trying to pinpoint children who can benefit from early intervention, since language delays can have long-lasting negative effects on a child's education and behaviour.
Diane Pesco, an assistant professor in Concordia's Department of Education, and her co-author Daniela O'Neill of the University of Waterloo, have found that low scores on early language testing were an accurate predictor of language problems at age of 5 and 6.
The pair examined the test scores of about 350 children over a number of years. When they were between the ages of 18 months to four years, the children's parents filled out a widely used questionnaire called the Language Use Inventory. (The Language Use Inventory was developed by Prof. O'Neill in 2009.)
"Children who score below a cut-off on the LUI have a much higher risk of having problems later, especially if the children are 24 to 42 months old," she says. The good news: Children scoring above the cut-off at any age are highly unlikely to manifest problems later.
In addition, Prof. Pesco, also a speech pathologist, says the study showed that testing before the age of 2 was unreliable. In the study, there was no strong connection between low scores for children 18 to 23 months of age and later language problems.
Waiting until 2 for testing may reduce the number of false positives and reduce stress on families and children.
"It seems like that's too early to really know," she says. "The age of 2 is a turning point where we start to see a pattern that is more likely to persist. Before that, anything can happen."
The LUI questionnaire captures not just vocabulary but also children's use of language in a social context: how they get a parent's attention, join a conversation, make jokes or use language to get things done.
As such, words and language are a window into a much broader range of abilities. For instance, children's use of words like "think" and "know" reflect a child's growing understanding of other people's preferences and thoughts.
"It's related to social competence," she says.
This is a useful way for parents to frame their children's language development, too. Instead of treating words and language as an academic subject, consider them as tools for rich conversation.
While reading a book, instead of asking "What is this?" while pointing to a page, ask "Why do you think that boy ran after the dog?" she says.
When talking with children, she suggests parents consider striking a balance between a child's language comfort zone and more challenging concepts.
"We want to scaffold them toward more complex language," she says.