Your 18-month-old just dumped out a box of cereal, left a trail of toilet paper around the house and poured a half-gallon of milk for the cat. Is there anything going on upstairs, you wonder?
Plenty, according to a study of babies and language that was done in Baltimore a few years ago. Its findings are still relevant today, and obviously of great interest, when the popularity of this YouTube video is considered: it shows two seventeen-month old twins seemingly having an involved conversation.
On her blog the mother of twins Sam and Ren had the following to say about this astonishing videoclip on her blog:
"We've had a fascinating time seeing language blooming around here," the boy's mother said Wednesday at her twinmamarama.com blog devoted to being a twin sister raising twin boys.
"Now the experts weigh in on this kind of twin language," she continued.
"I remember my own folks talking about my sister and I sending out verbal signals (essentially squeaks and shouts) in an attempt to pinpoint the location of our twin sister around the house!"
Also from the blog is are the comments by Dr Roberta Golinkoff, education professor and director of the infant language project at the University of Delaware in Newark."Even before they have words, they know how conversation works,"
"They're producing syllables emphatically and using them for communication purposes," she said. "They're having a ball."
The study of language acquisition
The original Baltimore study stated that babies as young as 18 months were actually figuring out the complicated rules of language and grammar - the kind of thing that adults struggle with. And they're doing it without breaking a sweat.
"I don't think they're doing anything on purpose," said Rebecca Gomez, an assistant professor of psychology at Johns Hopkins University in Baltimore. "I think they're incredibly bright little information processors."
"It's part of the cognitive apparatus that infants can keep track of statistical regularity," Gomez says.
Cecile McKee, director of the linguistics programme at the National Science Foundation, agrees.
"Are they trying to get something that's complex? You bet," McKee says. "Do they have to try? I don't think so."
In Gomez's study, 18-month-old babies listened to strings of three words arranged according to regular, predictable rules. The researchers used made-up words such as "pel" and "jic" so the babies' previous exposure to language wouldn't interfere. In the word strings, for instance, if "pel" were the first of three words, then "jic" would always be the third word, with some other made-up word in the middle. The babies listened to the word strings for about three minutes, about how long they could pay attention.
It turned out that the babies did learn to recognise the grammar of the strings, the study says.
They subsequently were put in booths, on their moms' laps, with speakers on the left and right sides. On one side, a speaker would play, over and over, identical three-word strings that were "grammatical," meaning they followed the rules of the strings the babies had listened to earlier. Then, from the other side, a speaker would replay an "ungrammatical" string.
The babies oriented to the side with the "ungrammatical" string for much longer, Gomez says - an average of 7.3 seconds. By comparison, she says, they paid attention to the "grammatical" string for an average of 5.23 seconds.
"It's like they've figured out the rule and they're bored," Gomez said. "I think some things pop out for them perceptually. They're pretty adventurous in tracking language." Results of the study were presented at a recent meeting of the American Association for the Advancement of Science.
Early childhood specialists do have a nature-nurture split in their theories about learning, McKee said, with this study leaning toward the nurture side, suggesting grammar is learned, not already embedded in the brain. But she said that babies' development truly was a result of both nature and nurture.
Still, what was interesting about the Hopkins study, she says, is that it allowed us to peer into the heads of really young children. Studies have looked at babies' sound patterns, discovering that four-month-olds can recognise their own names and the sound patterns of new words, she says, while others have looked at how older toddlers combine whole words and phrases in sentences. But there's been a gap in the middle, she says - the area of early toddlers, who understand a lot but can't yet communicate much.
Until now, she says, we haven't understood anything about early acquisition of grammar.
What the infants in the Hopkins study showed was an ability to piece together a highly abstract concept, McKee says. "That is fancy - really, really fancy," she said.
Gomez believes the findings suggest something different from the common belief that babies are born with an embedded sense of grammar.
"There's a good possibility the rules themselves aren't programmed," Gomez says. "What we may be programmed with is the ability to learn."
(Health24, updated March 2011)
Health24 readers' questions about twins to our experts