Arthur S. Reber examines the phenomenon of implicit learning, which involves acquiring knowledge about the rule-governed complexities of a stimulus environment without conscious effort. The article reviews two experimental paradigms—synthetic grammar learning and probability learning—and integrates them with other approaches to unconscious cognition. Key findings include: 1. **Tacit Knowledge**: Implicit learning produces an abstract and representative knowledge base that is optimal for solving problems and making decisions in novel situations. 2. **Unconscious Acquisition**: This knowledge is acquired independently of conscious learning efforts. 3. **Application in Problem Solving**: The tacit knowledge can be used implicitly to solve problems and make accurate decisions about novel stimulus circumstances. The article also discusses various epistemological issues, such as intuition, neuroclinical disorders of learning and memory, and the relationship between evolutionary processes and cognitive science. The author emphasizes the importance of understanding how complex knowledge is acquired, highlighting the need to explore both explicit and implicit learning processes in a wide range of contexts. The experimental procedures, including synthetic grammar learning and probability learning, are described in detail, and the results are discussed in relation to the acquisition of implicit knowledge. The article concludes with a discussion on the nature of mental representation and the role of explicit and implicit processes in learning and problem-solving.Arthur S. Reber examines the phenomenon of implicit learning, which involves acquiring knowledge about the rule-governed complexities of a stimulus environment without conscious effort. The article reviews two experimental paradigms—synthetic grammar learning and probability learning—and integrates them with other approaches to unconscious cognition. Key findings include: 1. **Tacit Knowledge**: Implicit learning produces an abstract and representative knowledge base that is optimal for solving problems and making decisions in novel situations. 2. **Unconscious Acquisition**: This knowledge is acquired independently of conscious learning efforts. 3. **Application in Problem Solving**: The tacit knowledge can be used implicitly to solve problems and make accurate decisions about novel stimulus circumstances. The article also discusses various epistemological issues, such as intuition, neuroclinical disorders of learning and memory, and the relationship between evolutionary processes and cognitive science. The author emphasizes the importance of understanding how complex knowledge is acquired, highlighting the need to explore both explicit and implicit learning processes in a wide range of contexts. The experimental procedures, including synthetic grammar learning and probability learning, are described in detail, and the results are discussed in relation to the acquisition of implicit knowledge. The article concludes with a discussion on the nature of mental representation and the role of explicit and implicit processes in learning and problem-solving.