Individual variation and constraints on language learning

If I had chosen to speak Chinese to my daughter instead of English, she would have grown up speaking differently than she does now. If I had chosen to speak to her only with loud music in the background, then it would be no surprise if her language development was delayed. And I wouldn't expect much better results if I had only spoken to her when she was engrossed in some other activity. This is all ratber obvious. Children learn the language tbat they are exposed to; dramatic corruption of the input affects what they can learn from it; and it helps when children attend to what people say to them. So it is surprising indeed to read that theories of language learning are seriously undermined by the finding that different language input leads to different learning outcomes. Yet this is what Ewa D^browska claims here and in other works. This is unfortunate. D^browska and her colleagues are making valuable discoveries about the scope of language abilities across the population, and these results should be relevant to any model of language learning. But by using these findings to fuel the tension between socalled 'generative' and 'usage-based' accounts of language learning little progress is made. Much more could be gained by probing more deeply into the source of individual differences. D^browska finds that adults with different educational backgrounds perform differently in tasks that require attention to morphological, syntactic, or semantic details. Speakers with low academic achievement are less likely to comprehend implausible passives (The dog was bitten by the man), sentences with sentential subjects (Paul noticed that the fact that the room was tidy surprised Shona), or sentences with universal quantifiers (Every fish is in a bowl). She argues that the individual differences in comprehension profiles reflect different grammatical endstates in learners of the same language. Additionally, she argues that this evidence challenges what she refers to as the Convergence Argument, which she regards as "one of the strongest arguments for an innate language faculty." The convergence