Which of the following is one of the four cornerstones of adult learning?

Adults learn by doing is a fundamental principle of adult education, emphasizing the idea that experiential learning enhances understanding and retention of information. This approach recognizes that hands-on experience and practical application of knowledge allow learners to engage deeply with the material. It encourages active participation, which is especially important for adults who often bring prior experiences and knowledge to the learning environment.

When adults engage in activities where they can apply what they have learned, they are more likely to retain information and develop skills that are directly applicable to their personal and professional lives. This contrasts with more passive forms of learning, such as lectures, which may not cater as effectively to the adult learner's need for practical application.

In the context of the other options, the focus on competition in learning (as suggested in another choice) detracts from the collaborative and experiential nature that adult learners often value. Additionally, the preference for lectures over discussions does not align with the interactive learning style that is beneficial for adults. Lastly, isolating learning experiences can hinder the social interaction and shared insights that are crucial for deeper understanding, which adults often seek in their educational experiences.