A culture of learning is one that encourages ongoing inquiry and questioning. It is comfortable with the fact that there is always more to learn and explore, and therefore the "work" of learning is never-ending. Learning is at the core of all research and development. The more you approach work with a sense of curiosity and inquiry, the more you can research and develop new approaches.
This can be a challenge for foundation staff or board who are geared toward finding the "one" solution to a challenge, checking it off the list, and moving on. But the culture of learning and ongoing inquiry is why cell phones now fit in the palm of your hand, and why more cancers are now curable with less stress for patients.
Learning isn't that helpful if it's only happening inside the heads of a foundation's internal team. Learning should be intentional, documented, and shared. That means making room for reflection by creating formal or informal systems or processes for reflection and discussion, as well as documenting and sharing learning on a regular basis.
Learning cultures can reflect the personalities of their organizations. For example, Google gives employees one day each week to suspend normal work and focus on inquiry and innovation. The software-developer community InfoQ crowdsources its employee learning, allowing staff to post information they'd like to learn and information they'd like to share. When interests align, those who wish to share join those who wish to learn during a brown-bag lunch. The company also hosts a series of two-hour "deep dive" trainings when staff wish to learn more. Many foundations I work with host regular brown-bag lunches for staff to learn about or discuss issues related to their work. The Kate B. Reynolds Charitable Trust even maintains a specific reserve fund for "just-in-time" learning. If an initiative or grantmaking program appears to be struggling, or a new opportunity arises, the Trust can immediately call in an expert, conduct a quick survey, convene key advisors or stakeholders, or do any number of things to learn and apply that learning in real time.
Introspection and learning take an investment of time - but it's time well spent. Remember that intentional learning can feel as though you are purposefully hunting for failures, so it's important to keep an eye out for things done well in addition to areas for improvement. In either case, the key is to find opportunities that the foundation can embrace in real time as its work progresses, rather than waiting for a post-mortem evaluation, when it's too late to increase impact.