UPDATE: Much thanks to Dorothy Bishop, Professor of Developmental Neuropsychology, Department of Experimental Psychology, University of Oxford for emailing me a copy of the original paper. I am reading it now and hope to post a more substantive review of the actual article later. For now, I've added just a few points in orange below.
But that's the conclusion of the anonymous journalist/stenographer from the Science Daily who wrote the recent story Building Language Skills More Critical for Boys Than Girls, Research Suggests. The author states Developing language skills appears to be more important for boys than girls in helping them to develop self-control and, ultimately, succeed in school.
Unfortunately I cannot find the original article (citation below) freely available, so all I have to go on is the brief description from the Science Daily piece:
The researchers examined data on children as they aged from 1 to 3 and their mothers who participated in the National Early Head Start Research and Evaluation study. As with previous research, Vallotton and Ayoub found that language skills -- specifically the building of vocabulary -- help children regulate their emotions and behavior and that boys lag behind girls in both language skills and self-regulation.
What was surprising, Vallotton said, was that language skills seemed so much more important to the regulation of boys' behavior. While girls overall seemed to have a more natural ability to control themselves and focus, boys with a strong vocabulary showed a dramatic increase in this ability to self-regulate -- even doing as well in this regard as girls with a strong vocabulary (emphasis added).
I cannot speak directly to the methodology without access to the original article. My guess is that there was some attempt to qualitatively correlate scores on vocabulary tests to either records of bad behavior or observed behavior. I could be wrong.
UPDATE: They measured two linguistic features, talkativeness and vocabulary, in 120 kids aged 14 months, 24 months, and 36 months: "Mother–child dyads were videotaped at home for 10 min in a semi-tructured play task ... Every vocalization by mothers and children was transcribed ... a trained observer used the Bayley Behavior Rating Scale (BBRS; Bayley, 1993) to rate the child’s ability to self-regulate. Children were rated on each of seven items which included behaviors such as their ability to maintain attention on the tasks, their degree of negativity, and their adaptation to changes in testing materials."
But I'm skeptical about the claims in Science Daily because it strikes me as the sort of thing that would take years of studying and dozens of researchers to come to any definite conclusions about (UPDATE: I remain skeptical about the Science Daily claims, but those are distinct from the claims in the original article).
UPDATE: According to the original article, there are well established empirical methods for judging a child's "expressive language".
This seems to be a case of over-interpretation with the intent of building actionable policy directives. I understand and sympathize with the impulse to translate scientific research into something directly useful that a teacher can implement today. Look, all you have to do is help boys build their vocabulary and they will behave themselves better! Unfortunately, it is rarely wise to make that leap so quickly.
UPDATE: There certainly is something here. I'll need more time to digest the methods and results to comment further.
Vallotton, C., & Ayoub, C. (2010). Use your words: The role of language in the development of toddlers’ self-regulation Early Childhood Research Quarterly DOI: 10.1016/j.ecresq.2010.09.002