“The question of whether learners must be aware that they are ‘noticing’ something in the input is the object of considerable debate. According to information processing theories, anything that uses up our mental ‘processing space’, even if we are not aware of it or attending to it intentionally, can contribute to learning. From a usage-based perspective, the likelihood of acquisition is best predicted by the frequency with which something is available for processing, not by the learner’s awareness of something in the input.”