The present study investigated a group of cognitive individual differences considered advantageous in second language learning and their role in language learning under implicit and explicit feedback conditions using both language awareness and language development measures. The study further investigated whether different types of awareness are related to language development. One hundred and twelve intermediate English learners of Spanish at a US university were administered tests from two language aptitude test batteries (Hi-LAB and LLAMA) and were randomly assigned to an implicit feedback (recast), explicit feedback (explicit correction), or control group. The two feedback groups received feedback on the target linguistic form (i.e., Spanish noun-adjective gender agreement) according to their group assignment in two treatment sessions. Learners’ knowledge of the linguistic target was measured using a grammaticality judgment test and an OPT immediately before the treatment and immediately after the treatment. Learners’ ability to notice the corrective function and linguistic target of the feedback was measured by means of a post-task debriefing questionnaire. Implicit sequence learning ability and error awareness predicted the implicit group’s pretest-posttest improvement, whereas phonological short-term memory predicted the explicit group’s pretest-posttest improvement. Phonemic coding ability, attention control, and processing speed further predicted learners’ awareness in the implicit feedback group.