I’ve been saying this for years. My colleague Mary Anne Nericcio says she’s been saying this for 30 years– I guess I’ve been saying it for about that long too! As part of our Diagnostic Markers of Language Impairment in Bilingual Children project, funded by the NIH (NIDCD) we screened some 1200 children who spanned the range from monolingual Spanish speakers to monolingual English speakers and looked to see whether children in the middle (bilinguals) were more likely to fall in the risk range more often than monolinguals. They don’t.
The findings of our paper appear in the American Journal of Speech-Language Pathology if you want to read the nitty-gritty, but I’ll give you the highlights here. What we did is screen a bunch of kids in Utah and Texas over a 3-year period. Children were ALL screened in Spanish and English. I’ve mentioned this procedure before– we wanted to know how much exposure was associated with their actual performance (we’re working on a paper on this currently, and I’ll tell you about it once it’s done). And a problem sometimes in bilingual research (and testing bilingual children) is that we can make mistakes about what a child’s better language is, and kids often have distributed knowledge so it’s best to test in both. As part of the screening procedure we interviewed parents asking them what language their child uses and hears each hour of the day to estimate how much they are exposed to each language per week. Right now I think we’re going to call this questionnaire the Language Interview Parent Survey (LIPS)– too cute??
Our results showed that on average, bilinguals scored lower than monolinguals in both languages. That is, bilinguals scored lower in Spanish than Spanish functional monolinguals and lower in English than English functional monolinguals. We call these kids functional monolinguals, because even if they have as much as 20% exposure to the language they really can’t communicate in it, tell a story, or respond in that language.
Anyway, you might be asking how the bilinguals can score lower in two languages and STILL not have an increased risk for language impairment. Good question. Although it seems a little counter-intuitive, this is indeed the case, they scored lower, but they didn’t fall below the cutpoint any more often than the monolinguals. How was this possible? We looked at the patterns of failure. Our cuts were set at the 25th percentile. And we considered children to “fail” the screener (which, clinically would indicate need for additional testing, because screeners usually are too short to be diagnostically accurate) if they fell below the 25th percentile on at least 3 of the 4 subtests. Predictably, the monolinguals failed in the language they didn’t know– but they scored the highest in the language they did know. To fail, they needed to score low in one of the subtests in the language they did know. Bilinguals were all over the place in terms of their patterns. When they failed, it could be in Spanish OR in English. When they passed, they might have a low score in one or two subtests (in Spanish or English or both) and score high on two or more subtests (again, Spanish, English or both). I think that because of this pattern, the averages for the bilinguals were lower because their lowest scores could be in either language, not just in one. So, they might do well in Spanish morphosyntax and English semantics, or English morphosyntax and Spanish semantics, or Spanish morphosyntax and semantics, or English morphosyntax and semantics. Whew!
Clinically, I think this means that unless children are functionally monolingual, you really need to test in both languages. You also can’t expect that their strongest language is consistent across domains. In fact, “mixed dominance” seems to be more the norm than not.
2 Languages 2 Worlds 
#1 by Stephanie Charpentier Muñoz on August 21, 2011 - 3:36 pm
Thank you so much for posting about this study. As a future SLP (currently taking prerequisite courses for graduate school), I am extremely interested in research related to bilingual language development. It amazes and saddens me how often I hear about SLPs who tell parents that bilingualism DOES increase the risk for language development, even though that position is not supported by the evidence! I have been following your blog for a year and appreciate the insight and knowledge that I gain from each post. Thank you!
#2 by Elizabeth D. Peña on August 21, 2011 - 5:10 pm
Thanks for your comments Stephanie, I have also heard about SLPs who tell parents that they need to pick only one language to speak to their child. The other thing I’ve heard is that they will tell parents of children with language impairment that they need to shift into one language because they won’t be able to handle two languages. Neither of these positions is based as you said, on evidence. We’re not the only ones to find that bilingualism doesn’t increase risk. Kohnert & Windsor, Paradis & Rice have also reported similar findings. Our findings are based on a large dataset which allowed us to examine bilinguals with different levels of exposure to the two languages– and we STILL didn’t find additional risk!
#3 by Amber Muhinyi on January 13, 2012 - 1:50 am
Thank you for taking the time to write these posts.- they’re stimulating and easy to read! I’m an undergraduate SLT in England and have found this a great resource which has directed me to some really interesting and relevant reading!
This is the first time I have come across the idea of ‘mixed-dominance’ in bilingual children… it completely makes sense to assess in both languages with this kind of evidence! Wow! What I would like to know is: what causes this phenomenon? I’ve been reading about how input affects output in language acquisition and development, and how that relative amount of exposure in a language a determines the child’s performance in that language. So why is it that we see different performance across language domains? Is it only in, say, semantics versus morphosyntax, due to vocabulary exposure in different settings (eg. more vocabulary used at school which is in L2), or do you expect to find it across other language domains?
#4 by Elizabeth D. Peña on January 13, 2012 - 8:21 am
Amber– thanks for your comments and questions. I think that mixed dominance makes a lot of sense for more kids than we realize. In an analysis of about 170 kids who had exposure to Spanish and English of at least 20% in each language, we found that about 60% demonstrated mixed dominance on a combination of 3 measures– two morphosynax (cloze and sentence repetition) and 1 semantics. Johanne Paradis has found this as well with French-English bilinguals. We have a new paper coming out in Bilingualism: Language & Cognition in which we explore this more carefully, so I’ll probably post about that some time in the next couple of months. But, it may have to do with a combination of development and exposure to different kinds of things in each language. So, regarding development, kids need to know some number of words before they can put them together into sentences. Then they need to start learning the details of the grammar. So, they might show shifting dominance to L2 in vocabulary before they show that in grammar. Exposure at home and school may emphasize different sorts of content and so kids may learn vocabulary especially, that goes with that context. It will be interesting to see evidence for this in other domains such as phonology and narratives.
#5 by Amber Muhinyi on January 15, 2012 - 6:52 am
So interesting! Thanks, I’ll look out for that paper.
#6 by Angela Somawang on February 23, 2012 - 10:35 am
I have told many parents who are afraid to teach their kids two languages for fear of confusing them that they should in fact teach them both. I am sure as these kids get older they will become more proficient in both languages but need more exposure. Even students who are monolingual have trouble with language, but knowing a second language will definitely help these children in adulthood! I certainly wish I knew a second language! Thank you for sharing!
#7 by Seun Bunmi on August 21, 2012 - 7:06 pm
yeah! A child that is exposed to two languages will not be confused especially when the exposure is before his/her critical age. however, it has been discovered that bilinguals who speak their L1 perfectly perform better than those whose L2 have subtractive influence on their L1
#8 by Seun Bunmi on August 21, 2012 - 7:09 pm
How about that?
#9 by the speech monster on October 11, 2012 - 9:46 pm
Hi,
I’m an SLP and am constantly surprised that, despite all the research supporting bilingualism and that it does not increase the risk for language difficulties, professionals keep telling parents to stick to speaking in English (the language of the majority). Even after I tell parents not to restrict their child’s language input, it still happens This causes a potential cultural backlash in the future.
I have a question, however, about whether a child with a known/diagnosed language disorder should be dissuaded from picking up a second language in middle or high school, given their difficulties in language? We’re not talking about a language that they have already been introduced to at a young age.
Does this same concept apply?
C
#10 by Elizabeth D. Peña on January 5, 2013 - 1:50 pm
Hi speech monster, sorry its taken so long for me to reply. I’m not really sure about learning an L2 during the middle school years, but I think that the same principles could apply. It’s often the case that learning a second language helps middle school children develop meta awareness of language generally. The other day I was driving the high school carpool kids who were studying for their Spanish semester final. One commented that they knew more about English grammar now that they were taking Spanish. So that could be helpful. The key for their success is to practice probably a lot more than what a typical kid might need, so there would need to be an awareness of that as well. But, really, we don’t know for sure. My prediction is that it would likely be difficult, not impossible and that there could be some positive benefits.