The article discusses the concept of "desirable difficulty" in learning, suggesting that if something comes too easily, it won't stick. This concept was developed by Nate Kornell, a psychologist focused on memory and learning at Williams College in Massachusetts, who suggests that "spacing" and "interleaving" are effective strategies for learning. These findings could lead to more productive forms of "brain training" than a random computer game designed to improve intelligence. Older people may find their curiosity piqued by something relevant to their self-interest or something they already know about. The article also suggests that learning new skills and taking on new hobbies can increase your curiosity and relieve stress.