Today, Martin Shipton reported that an expert witness in a custody case testified that, “Welsh medium education could cause mental retardation in some children.” While the details of specific case are unknown, it seems that the expert believes that either Welsh causes mental retardation or that bilingualism causes mental retardation. Neither of these of course is true, but it brings up some of the same arguements that we hear over and over again. Can children handle two languages? Do children who divide their attention between two languages learn either one well? Yet, all over the world, children can and do operate in more than one language.
In the U.S., many children learn a language other than English at home and then learn English when they start school. This is an example of early sequential bilingualism. What we do know is that the first language often influences learning in the second language. Sometimes children will transfer what they know in one language to what they they are learning in a second language. This is a normal consequence of having contact with more than one language. We also know based on research I’ve been involved with (see here or here) and work that for example, Barbara Pearon has done that children learn words in each of their two languages depending in part on what goes on in each of those situations. So, children– at least in the early stages of learning two languages may now know every word in both languages. We found for example that preschool and kindergarten children had only about a 34% overlap in words used in both Spanish and English. In an on-going study, it looks like older children may have a bit more overlap, but we’ll see once the data are all coded and analyzed whether this is the case. These data have implications for how one interprets or judges language ability in children who speak more than one language. It seems obvious, but I’ll say it anyway. When testing bilingual children’s language BOTH their languages need to be tested. What’s known in language 1 or L1 needs to be put together with what’s known in language 2 or L2.