One important consideration is whether the person has opportunities forformal language learning. Contrary to popular belief, simply immersing an adult in an English-speaking environment rarely works – we don’t need to look further than the struggles of many migrants, even highly educated ones, who came to English-speaking countries as adults for evidence of that. Looking specifically at university students, though, there is research on this. Pamela Humphreys, as part of her Ph.D. studies, sent a large number of students for IELTS tests at the beginning and end of their three-year university degrees and compared the results. She found that the average score gain was 0.3 of an IELTS band score, a barely noticeable difference – and that many students went backward.
So, studying in a higher education course by itself clearly doesn’t do much for a person’s English language proficiency; language learning in adults doesn’t occur simply by ‘exposure’ or ‘osmosis’ – time – and quite a considerable amount of time at that – must be devoted explicitly to language learning activities. While it’s common to hear stories about people who migrated to an English-speaking country as young children rapidly developing a high level of proficiency, at least in spoken ‘playground’ language, this ability disappears after roughly late primary school. This is known as the ‘critical period’ – see, for example, Lightbown and Spada (2013.
So, given that simple exposure isn’t enough, and formal language learning is necessary, the next question is how much formal learning is needed? Research in this area is tricky because of the difficulty in finding a large uniform sample and limited research funding in the area generally, but Kathy Elder and Kieran O’Loughlin (1998) looked at 112 students very roughly concluded that:
To gain a deeper insight into this variation, Pearson has published a summary of research on language proficiency gain (Benigno et al, 2017). The consensus shown within the report demonstrates a clear pattern – that a significant factor is the ‘distance’ between the learner’s first language (or languages) and the language they’re learning. For example, people who grew up speaking Chinese or Arabic can take two to three times longer than those who grew up speaking French or German to make the same gains in English proficiency. Looking in more detail and taking moving from IELTS 6.0 to 6.5 as an example, their research shows that students can take anything from around 300 to over 700 hours*, suggesting that Elder and O’Loughlin’s research may have been optimistic.
Benigno, V., de Jong, J., & Van Moere, A. (2017). How long does it take to learn a language? Insights from research on language learning (Global Scale of English Research Series). Pearson.
Elder, C., O’Loughlin, K., & IELTS Australia. (2003). Investigating the relationship between intensive English language study and band score gain on IELTS (Volume 4; IELTS Research Reports). IELTS Australia.
Humphreys, P. (2018). What is this thing called academic English language proficiency? From theory to principled practice. UECA PD Fest, Sydney.
Lightbown, P. M., & Spada, N. (2013). How Languages are Learned 4th edition. Oxford Handbooks for Language Teachers. Oxford University Press.