The Science of Learning and the Learning of Science

 Introducing Desirable Difficulties

By Robert A. Bjork and Marcia C. Linn

Students' performance during instruction is commonly viewed as a measure of learning and a basis for evaluating and selecting instructional practices. Laboratory findings question that view: Conditions of practice that appear optimal during instruction can fail to support long-term retention and transfer of knowledge and, remarkably, conditions that introduce difficulties for the learner — and appear to slow the rate of the learning — can enhance long-term retention and transfer. Such "desirable difficulties" (Bjork, 1994) include: spacing rather than massing study sessions; interleaving rather than blocking practice on separate topics; varying how to-be-learned material is presented; reducing feedback; and using tests as learning events.