A time for telling

Suggestions for improving text understanding often prescribe activating pri or knowledge, a prescription that may be problematic if students do not hav e the relevant prior knowledge to begin with. In this article, we describe research about a method for developing prior knowledge that prepares studen ts to learn from a text or lecture. We propose prior knowledge that prepare s students to learn from a text or lecture. We propose that analyzing contr asting cases can help learners generate the differentiated knowledge struct ures that enable them to understand a text deeply. Noticing the distinction s between contrasting cases creates a "time for telling"; learners are prep ared to be told the significance of the distinctions they have discovered. In 3 classroom studies, college students analyzed contrasting cases that co nsisted of simplified experimental designs and data from classic psychology experiments. They then received a lecture or text on the psychological phe nomena highlighted in the experiments. Approximately 1 week later, the stud ents predicted outcomes for a hypothetical experiment that could be interpr eted in light of the concepts they studied. Generating the distinctions bet ween contrasting cases and then reading a text or hearing a lecture led to more accurate predictions than the control treatments of (a) reading about the distinctions between the cases and hearing a lecture, (b) summarizing a relevant text and hearing a lecture, and (c) analyzing the contrasting cas es twice without receiving a lecture. We argue that analyzing the contrasti ng cases increased students' abilities to discern specific features that di fferentiated classes of psychological phenomena, much as a botanist can dis tinguish subspecies of a given flower. This differentiated knowledge prepar ed the students to understand deeply an explanation of the relevant psychol ogical principles when it was presented to them. These results can inform c onstructivist models of instruction as they apply to classroom activities a nd learning from verbal materials. In particular, the results indicate that there is a place for lectures and readings in the classroom if students ha ve sufficiently differentiated domain knowledge to use the expository mater ials in a generative manner.