This paper presents the main tenets of two paradigms of investigation of human cognition _ the symbolic and the connectionist _ and discusses how research in each paradigm has fed studies in L2 learning. The symbolic paradigm explains the acquisition and use of knowledge through the existence of mental representations, logical rules, and symbols. The connectionist paradigm claims that human cognitive processing is related to how neurons are interconnected in the brain. The paper also examines how constructs such as types of knowledge, types of memory, input processing, and attention are presented in the two theories and how these constructs relate to current L2 research.