Carmen Muñoz is Professor of English Linguistics and Applied Linguistics at the University of Barcelona, and the researcher most closely identified with serious empirical work on age effects in instructed, foreign-language settings. She trained at Reading (MA, Applied Linguistics) and Barcelona (PhD, English Linguistics), and built a research group around the idea that the naturalistic-setting findings on age — younger is better — do not straightforwardly transfer to classrooms.
The Barcelona Age Factor (BAF) Project is her signature contribution. Running across years and cohorts, it compared learners who had started English at different ages inside the Spanish school system, controlling for hours of exposure. The consistent result, well summarised in Age and the Rate of Foreign Language Learning (2006), is that later starters outperform earlier starters in rate of acquisition at equivalent exposure — a direct challenge to the policy intuition that "earlier is always better" in foreign-language classrooms. Her later work pushes into intensive exposure, extramural input, and the effect of subtitled audiovisual material on L2 learning.