The significance of cognitive processes in language learning, such as the mental processes learners bring to task learning, has been accepted by psycholinguistics and linguistics (Zhang, 2012). The presence of conscious and unconscious processes is of the essence in cognitive psychology. More specifically, whether learning takes place consciously or unconsciously is an important discussion for second language researchers. On the one hand, scholars such as Schmidt (1990) acknowledged that attention to input is a conscious process and is a necessary process to convert input to intake. Another cogent argument he put forward was that no matter whether a learner attends deliberately to a linguistic form in the input or it is noticed unintentionally, once it is noticed, it becomes intake. On the other hand, Krashen's (1982)- Input Hypothesis- explicitly rejected a role for consciousness language acquisition and believed that acquisition occurs once learners have access to an optimal amount of appropriate input, which in turn leads acquisition to happening naturally. Having said that the existence of unconscious learning cannot be denied completely, conscious learning is assumed to have an important role in L2 learning. In this paper, we will elaborate noticing hypothesis from both cognitive and ecological perspectives.