You might think that it does, from the headlines "Bilingual children stutter more – study", "Stutter risk for bilingual kids", "Study: bilingual kids more likely to stutter", etc. These stories report on a recently-published study: Peter Howell, Stephen Roger Davis, and Roberta Williams, "The effects of bilingualism on stuttering during late childhood", ADC Published Online 9 September 2008.
Howell et al. studied 317 children who stuttered, all of whom started school in the UK at age four or five, first came to a speech clinic between 8 and 10, and lived in the greater London area. For 69 of the 317, "at least one language other than English was spoken in the home". Thus 21.8% of the stutterers were raised in a home where a language other than English is spoken. In comparison, among schoolchildren of comparable age in the greater London area, the London Education Authority reports that 28.4% come from such homes.
But wait a minute: the percentage of stutterers who come from non-English-speaking homes is smaller than the percentage of kids in general who come from such homes? How does this translate into "Bilingual children stutter more", or "Stutter risk for bilingual kids"?
Well, hang on, we'll get to the connection between (a certain kind of) bilingualism and stuttering that the study suggests may exist. But to understand the argument, you're going to have to put up with some slightly complicated analysis and reasoning.
For 38 of the 69 bilingual stutterers, caregivers "primarily or exclusively" used a language other than English. This excluded the 31 children whose parents "opted to speak a language other than English in the home for their child’s educational/social advancement".
The researchers further subdivided the 38 selected stutterers into 15 LE ("late English") kids, who weren't exposed at all to English until they went to school, and 23 BIL kids, who already spoke both English and some other language when they started school.
And they selected a control group (FB) of fluent (non-stuttering) bilingual kids, age-matched to the stutterers, and also divided into LE and BIL subgroups in the same way.
Now let's look at the 2×2 contingency table for stuttering vs. non-stuttering and LE vs. BIL:
So if we accept that the FB controls were really matched in every other relevant way, we have some indication that a particular kind of bilingualism might be a risk factor for stuttering. Remember, we're talking about situations where 1) the caregivers speak "primarily or exclusively" another language, but 2) the kid learns English anyhow, for example from playmates or siblings — that's the case they call BIL. This is distinguished from the situations where 1) the caregivers speak "primarily or exclusively" another language, and 2) the kid doesn't learn any English from other sources — that's the situation that they call LE. (Again, we're entirely excluding the cases where the caregivers speak English as well as another language.)
Now, as the contingency table shows, among the stuttering bilinguals, 61% learned English before going to school (i.e. were in sub-group BIL rather than LE); among the fluent bilinguals, only 26% learned English before going to school.
If this were the question period after a presentation, I'd want to ask the authors these questions:
If (some forms of) bilingualism tends to cause stuttering, why is the proportion of non-English-speaking homes among stutterers (in your study) actually lower than in the general school population population? I know that you say the difference is not statistically significant, but you report p= 0.054, which is pretty darn close to p=.05. Shouldn't we expect a difference in the other direction — which you surely didn't find?
If early bilingualism tends to cause stuttering, why did you remove from the study those early-bilingual kids whose caregivers spoke both English and some other language? Does early bilingualism tend to cause stuttering only if the socially-dominant language (here English) is learned from siblings or playmates rather than from parents? If so, why?
The family situations of LE and BIL kids are likely to be rather different — for example, BIL kids presumably tend to live in more ethnically mixed social situations than LE kids do. Could this (rather than the early bilingualism itself) be responsible for the apparent increase in stuttering?
Prof. Howell and the other authors may very well have good answers for these questions. Perhaps they even answered them in their paper, and I missed it on a quick read this morning. But those are the questions that the paper left me with.
[I should note in passing that there hasn't been a lot of media uptake on this story, which surprises me a bit given the generally high level of interest in bilingualism. Maybe the press release didn't hit the right wires; or maybe there's been too much other news, what with tropical storms, financial meltdowns and U.S. politics. Or then again, maybe most editors took a look and decided to pass this one up. If you have any insight into this process from the inside, please share it with the rest of us.]