Vicki Swisher has an interesting piece on Businessweek.com about the types of jobs that can be the most powerful learning/developmental experiences for managers.
Swisher points to research by the Center for Creative Leadership (CCL) which shows that formal training accounts for only a small fraction of the learning/knowledge that managers need to to develop critical skills; the rest comes from experience. This finding is certainly no surprise. Formal training can only do so much. The real role for formal training has to be in helping managers accelerate the learning through experience that takes place on the job. It can do so in a number of ways. For instance, formal training can introduce managers to new ideas or perspectives, enable sharing of knowledge across the organization, help managers reflect on their experiences and identify ways to improve, and give executives access to practices and techniques being employed in other organizations so as to prevent a firm from becoming overly insular.
Still, Swisher rightfully points out that not all experiences are equally useful as development learning opportunities. Her list of what research shows to be the most useful developmental jobs is quite intriguing.