The previous chapters have outlined the theoretical background, basic assumptions, and some key applications of Cognitive Load Theory (CLT) in its current state of development. The fundamental idea underlying CLT is that instructional design decisions should be informed by the architecture of the human cognitive system. CLT can therefore be described as a cognitive theory of instructional design. CLT has been very influential in educational research since the 1980s. It has inspired a growing number of research studies aimed at deriving empirically based guidelines for instructional design. Moreover, at its present stage of development, CLT is arguably one of the most influential instructional design theories.

However, the extant research on cognitive load raises questions about the assumptions underlying CLT, some of which have not been consistently supported by the empirical data, suggesting the need to update the theory by incorporating recent empirical findings on cognition and learning (Schnotz & Kirschner, 2007). The first goal of this chapter is to summarize the theoretical developments of CLT and highlight some of its strengths and limitations.

An additional contribution of CLT research includes efforts to develop practical, valid, and reliable measures of its main construct: cognitive load. However, as suggested in Chapter 9, the existing body of cognitive load research fails to exhibit methodological consistency regarding cognitive load measurement and lacks appropriate methods to measure other relevant constructs, such as the different load types proposed by the theory (DeLeeuw & Mayer, 2008).

THE PROBLEM OF COGNITIVE LOAD MEASUREMENT: WHAT ARE GOOD COGNITIVE LOAD INDICATORS?

The previous chapters have outlined the basic theoretical assumptions for cognitive load theory (Chapter 2), described how cognitive load affects the process of schema acquisition (Chapter 3), and discussed the role that learners' individual differences play in the process of knowledge construction (Chapter 4). The central problem identified by Cognitive Load Theory (CLT) is that learning is impaired when the total amount of processing requirements exceeds the limited capacity of human working memory.

In addition to the fundamental assumption that learning is a function of available cognitive resources, CLT makes some additional assumptions with respect to the relation among cognitive resources, demands, and learning. The first of these additional assumptions is that instructional design and/or methods may induce either a useful (germane) or a wasteful (extraneous) consumption of cognitive capacity. The second assumption is that the source of cognitive load can also vary depending on the complexity of the task to-be-solved (intrinsic cognitive load defined by element interactivity). There is a large body of empirical research supporting the assumptions of CLT by analyzing the relation between the factors influencing cognitive load and learning outcomes. For example, several empirically well-established instructional design principles (Mayer, 2005) were identified in that line of research, which are discussed in other chapters of this book (see Chapters 7, 8). However, can CLT's assumptions be verified directly?

What is Cognitive Load Theory (CLT)? The objective of CLT is to predict learning outcomes by taking into consideration the capabilities and limitations of the human cognitive architecture. The theory can be applied to a broad range of learning environments because it links the design characteristics of learning materials to principles of human information processing. CLT is guided by the idea that the design of effective learning scenarios has to be based on our knowledge about how the human mind works. Starting from this premise, different processes of knowledge acquisition and understanding are described in terms of their demands on the human cognitive system, which is seen as an active, limited-capacity information processing system. Taking into account the demands on cognitive resources induced by the complexity of the information to be learned, the way in which the instruction is presented to the learner, and the learner's prior experience and knowledge, CLT aims to predict what makes learning successful and how learning can be effectively supported by teaching and instruction.

Because of its applicability for a broad range of instructional materials, including Web-based and multimedia instruction, CLT is a frequently discussed concept in educational psychology and applied learning sciences. A growing body of empirical research has become available in recent years that describes the relationships among human cognitive architecture, the design of educational materials, and successful learning.