I’m frequently asked how bilingual children should be tested– that is, how both languages should be considered in language assessment. Here, I’m going to focus on assessment of vocabulary.
First, let’s start with an example. If a child know the color words: blue, green, yellow, rojo, azul, and morado, how many colors do they know? Well, it depends on how and what you measure. If you only measure English the answer is 3. If you only measure Spanish, the answer is 3 again. But, are they the same 3? Well, no. So, what should you do? Is the answer 6? Here’s a visual of the 6 colors named across the two languages:
But, if we count blue/azul one time (a conceptual approach), the answer is 5.
Vocabulary can be counted in a similar way. Words that are known in L1 can be counted and then compared to the words known in L2. A conceptual approach would mean counting each concept that is lexicalized rather than counting only words in one language. With bilinguals, words counted in only one language would likely underestimate what the child knows. On the other hand, the same concept counted twice might inflate what it is they know across their two languages.
I have to say though, that I’m not sure that adding what children know in their two languages wouldn’t be helpful. This approach in conjunction with a conceptual approach I think could tell us something about vocabulary depth– similar to development of synonyms. Synonyms carry slightly different meanings and what they evoke may not quite be the same thing. For example according to an on-line synonym dictionary, the word “larger” has 7 senses, if all these words were in a child’s vocabulary we would count them all. I think that the same thing can happen with translation equivalents. To individual people the translations may not be exactly equivalent. I don’t have any conclusions yet, but I will continue to explore the issue.