How effective are study groups?

Have you ever been part of a study group? What was it like?

You rarely hear much about study groups. There are frequent stories of people who master certain skills by practicing on their own or perhaps under the guidance of an instructor.

I don’t think there is a substitute for self-study, but it seems to me that being part of a study group could make things easier. There is a social aspect to it and proper use of friendly competition may spur people’s efforts. Additionally, if someone is stuck in learning something, others in the group may provide assistance. Those providing the assistance benefit by reviewing what they have learned.