In Chapter 1 the different medical study designs are discussed and the difference between age, period and cohort effects is explained. Furthermore, some general information (e.g. prior knowledge, software used for the examples) needed to work through the book is provided. Finally, there is a short section in which the differences between the second and third edition are outlined.

Beliefs are, or at least appear to be, integral to cognition and action. Though there are scarcely features of human psychology more intuitive to their bearers, beliefs are surprisingly elusive targets of study. In this chapter, we consider some perennial questions about beliefs and suggest that some clarity might be achieved by viewing beliefs through the lens of cognitive psychology. We discuss psychological findings and evolutionary considerations which seem to imply that the mind is not designed to form true beliefs, but beliefs that are instrumentally useful. This issue is redolent of debates over whether people are rational or irrational and whether beliefs aim at truth or serve other psychological functions. We survey a series of practical tradeoffs and computational constraints that limit the attainment of true beliefs, and which may be responsible for apparent irrationality. Additionally, the origin of false or irrational-seeming beliefs may be inadequately specified by behavioral data, which implies that a deeper understanding of processes and prior knowledge inside the head is essential for a science of beliefs. We conclude by noting that a view of irrational beliefs as the result of prior knowledge, rather than irrational processes, may have optimistic implications for improving people’s beliefs.

This chapter summarizes research and theory concerned with the effects of learner expertise (prior knowledge) on multimedia learning. According to the expertise reversal principle, in many situations, design principles that are effective for novice learners may not be effective or even hinder learning for more knowledgeable learners. The main theoretical issue associated with this principle concerns the integration in working memory of instructional information with knowledge structures held in long-term memory. The major instructional implication is the need to tailor instructional formats and procedures to changing levels of expertise. The chapter also suggests future research directions.

The learner control principle is that giving learners control over their instruction by allowing them to pace, sequence, and select information aids learning if learners possess high levels of prior knowledge and if they receive additional instructional support to orient themselves in the learning environment and to self-regulate their learning. Learner control has been suggested to afford an active, constructive processing of instruction, to increase and sustain the motivation to learn, to enhance the acquisition of self-regulatory skills, and to enable learners to adapt instruction to their preferences and needs. Despite these envisioned benefits, there is little empirical evidence supporting these claims, which is largely because these benefits are overwritten by the additional cognitive and metacognitive demands learner control imposes.

In this chapter, we review Ornstein’s contributions to the study of children’s memory strategy use to maintain information they are expected to remember, including barriers, supports, and application. We then discuss our own work on how children go beyond maintaining information to extending their knowledge base by going beyond what was explicitly provided and self-deriving new knowledge through integration of separate learning episodes. We examine the parallels in how knowledge is maintained and extended, including the role of prior knowledge. We conclude with three lessons learned from the work of Ornstein and colleagues that will enrich developmental science: move the research into ecologically relevant and even “high-stakes” contexts, conduct longitudinal work, and investigate the role of metacognition.