Susanne E. Carroll is a Canadian linguist, Professor Emerita of Linguistics at the University of Calgary, and the author of the most fully worked-out modular alternative to attention-based accounts of second language acquisition. Trained in generative syntax and semantics (PhD, Université de Montréal), she has spent her career on a question most input theories skate over: not whether input matters, but what counts as input in the first place, and what the mind must already be able to do for raw speech to leave any trace.
Her answer is set out in Input and Evidence: The Raw Material of Second Language Acquisition (2001), the book that introduced Autonomous Induction Theory. Carroll's starting move is to separate the acoustic signal a learner is exposed to from the structured representations a learner's processors actually build. Acquisition cannot work on the signal directly; it works on what the parser manages to encode, and it is driven by parse failure rather than by conscious attention. Much of her empirical work since has probed the earliest moments of contact with a new language, showing how learners segment and store unfamiliar words on first exposure and how heavily that depends on what they already know from the L1.
Carroll is the sharpest critic of Schmidt's Noticing Hypothesis. Her objection cuts deeper than the usual measurement complaints: the units acquisition operates on, phonemes, morphemes, syntactic categories, are mental constructs, not objects sitting in the sensory environment, so they cannot be "noticed" there at all. As she puts it, "the stuff of acquisition ... consists of mental constructs that exist in the mind and not in the environment ... If not present in the external environment, there is no possibility of noticing them" (Carroll, 2001, p. 47). Conscious noticing, on her account, comes too late and too coarse to be the trigger for grammatical restructuring, because the parser has already done its work below awareness. This is the line of attack Geoff Jordan adopts and names as closest to his own commitments.