Getting Out of Order: Avoiding Lesson Effects Through Instruction

This chapter describes two experiments that test the felicity-conditions hypothesis that people learn best if a task is taught one subprocedure per lesson. In these experiments, children were taught multiplication skills by a human tutor. Although there was a slight trend that presenting one topic per lesson led to fewer errors than presenting two topics, the more important finding is that there is better transfer to new problems when teaching two subprocedures per lesson: about one-third fewer errors at test. These results suggest that it is crucial to learn when to apply a particular element of knowledge. Lessons that deliberately change the element of knowledge needed from problem to problem are more difficult for learners but can enhance the learner's ability to apply different types of knowledge and to transfer their learning. This effect also suggests why textbooks have evolved to use one disjunct per lesson and is also consistent with good practice in system documentation. The study further suggests not only that teaching multiple items per lesson is safer if there is someone to help remove any confusion but also that some small amount of reordering by a teacher can help the learner to compensate for poor orders.