  Although cognitive science has discovered several methods for increasing the
learning of complex skills, such as physics problem solving, detailed
examination of verbal protocols suggests there is still room for improvement.
Basically, students do not always apply the meta-cognitive strategies that the
instruction invites. For instance, when prompted to self-explain, students may
still choose to not explain. We conjecture that most students know which
meta-cognitive strategies are good and bad. When they work in pairs, they are
more likely to choose the good strategies. We hypothesize that social
accountability improves meta-cognitive strategy choice, which thereby improves
learning. Our experiment compared individuals and pairs learning from
state-of-the-art instruction. The results suggest that the dyads solved more
problems and requested fewer hints during problem solving than individuals. We
also discovered a new form of self-explanation, wherein students generate
explanations to account for the differences between their solutions and the
instructor's.
