The construct "awareness" is undoubtedly one of the more difficult constructs to operationalize and measure in both second language acquisition (SLA) and non-SLA fields of research. Indeed, the multifaceted nature of awareness is clearly exemplified in concepts that include perception, detection, and noticing, and also in type of learning or learning conditions (implicit, explicit, incidental, subliminal), type of consciousness (autonoetic, noetic, anoetic), and type of awareness (language, phenomenal, metacognitive, situational). Given this broad perspective, this article provides, from a psycholinguistic perspective, a timeline on the research that addresses the role of awareness or lack thereof in second/foreign language (L2) learning.