Is 30% enough? On how much exposure a child needs to learn a language
If you’ve spent any time reading about raising bilingual children, you’ve probably bumped into the “30% rule”: the idea that a child needs to hear a language at least 30% of the time to actually learn it. The intuition behind this is reasonable: a language hardly heard is a language hardly learned. But research shows that bilingual language learning is more complex than just following the 30% input rule. Here’s why.
1. The input threshold shifts with age
30% input seems to be sufficient for young children, but may no longer be enough at a later age if you want your child’s language to keep developing with age. Silva-Corvalán followed children learning Spanish as a minority language alongside majority-language English [1]. Up to about age three, 25-30% input in Spanish was enough to keep development on a roughly typical track. But after age three, that same proportion stopped being sufficient. Not for basic conversations, but for the more complex grammar and vocabulary that older children need to keep developing. While the majority language English (in which they were getting 65-70% of their input) sailed along at the monolingual norm at this age, the minority language was no longer keeping up.
2. An estimated percentage isn’t always achieved
Research has shown that parents’ estimates of how much input they give their child are often off. Marchman and colleagues [2] found that actual measured child-directed speech (the real word counts) predicted language outcomes better than parents’ own estimates of the input they had given. In other words, if you ask a parent “What percentage of the day does your child hear the language?” their answer is likely a worse predictor than a recording would be. We’re not great at estimating our own language behavior. A family that believes their child is getting 40% of language X might actually be delivering 20%, and this is what the child’s progress will reflect.
3. Language input quality differs
The richness of the input (or how much children can learn from it) differs a lot between families. Weisleder & Fernald [3] documented huge differences in how much parents talk to their kids and how much of their speech was actually directed to the child, with child-directed speech leading to more learning. De Houwer’s work [4] also showed that parents vary not just in how many words they produce, but also in other characteristics like their speech rate. These differences in the quality of input don’t always line up with what parents think they’re doing. 20% of rich, interactive input can offer more learning opportunities than 30% of mostly passive, screen-based input.
In short, the answer to the 30% rule is more complex and nuanced than we think. Whether 30% is ‘enough’ depends on many things, like your child’s age and the quality of the input you offer. It’s probably best to use 30% as a minimum, especially as your child gets older, while keeping this in mind:
- Don’t blindly trust your own % estimate. Track the actual exposure your child gets for a week or two, and see if you’re really getting to your aimed percentage.
- Plan to increase input as the language demands of your child’s age grows. As your child gets older, their world gets bigger. The school language will automatically develop along. Try paying attention to mirroring this in the home language as far as you can, seeing if you can bump the amount of input as well as the linguistic difficulty. This means using more advanced words and sentence structures.
- Distinguish between ‘around the language’ and ‘in the language’. If your child overhears you speaking the language across the room or watches TV in the language, this is different from being asked questions and expected to respond. Child-directed speech (talking with rather than around your child) is more powerful for learning [3].
- Try to make the language input varied by exposing your child to different topics, media, genres, and speakers. Find more tips here on how to make language rich for learning.
My Languages, My World
A workbook for bilingual and multilingual children to explore their own language landscape. They reflect on when, where, and with whom they speak each language, and set their own language wish for keeping their languages close.
References
[1] Silva-Corvalán, C. (2014). Bilingual Language Acquisition: Spanish and English in the First Six Years. Cambridge: Cambridge University Press.
[2] Marchman, V.A., Martínez, L.Z., Hurtado, N., Grüter, T., & Fernald, A. (2017). Caregiver talk to young Spanish-English bilinguals: comparing direct observation and parent-report measures of dual-language exposure. Developmental science, 20(1). https://doi.org/10.1111/desc.12425.
[3] Weisleder, A., & Fernald, A. (2013). Talking to children matters: Early language experience strengthens processing and builds vocabulary. Psychological Science, 24(11), 2143–2152.
[4] De Houwer, A. (2018). The role of language input environments for language outcomes and language acquisition in young bilingual children. In D. Miller, F. Bayram, J. Rothman, & L. Serratrice (Eds.), Bilingual cognition and language: The state of the science across its subfields (pp. 127–153). Amsterdam: John Benjamins Publishing Company. https://doi.org/10.1075/sibil.54.07hou.