Cognitive load theory was introduced in the 1980s as an instructional design theory based on several uncontroversial aspects of human cognitive architecture. Our knowledge of many of the characteristics of working memory, long-term memory and the relations between them had been well-established for many decades prior to the introduction of the theory. Curiously, this knowledge had had a limited impact on the field of instructional design with most instructional design recommendations proceeding as though working memory and long-term memory did not exist. In contrast, cognitive load theory emphasised that all novel information first is processed by a capacity and duration limited working memory and then stored in an unlimited long-term memory for later use. Once information is stored in long-term memory, the capacity and duration limits of working memory disappear transforming our ability to function. By the late 1990s, sufficient data had been collected using the theory to warrant an extended analysis resulting in the publication of Sweller et al. (Educational Psychology Review, 10, 251–296, 1998 ). Extensive further theoretical and empirical work have been carried out since that time and this paper is an attempt to summarise the last 20 years of cognitive load theory and to sketch directions for future research.

Cognitive load theory has traditionally been associated with individual learning. Based on evolutionary educational psychology and our knowledge of human cognition, particularly the relations between working memory and long-term memory, the theory has been used to generate a variety of instructional effects. Though these instructional effects also influence the efficiency and effectiveness of collaborative learning, be it computer supported or face-to-face, they are often not considered either when designing collaborative learning situations/environments or researching collaborative learning. One reason for this omission is that cognitive load theory has only sporadically concerned itself with certain particulars of collaborative learning such as the concept of a collective working memory when collaborating along with issues associated with transactive activities and their concomitant costs which are inherent to collaboration. We illustrate how and why cognitive load theory, by adding these concepts, can throw light on collaborative learning and generate principles specific to the design and study of collaborative learning.

Cognitive load theory has been in development since the 1980s. Much of the impetus for that development has come from firstly, replication failures using randomised controlled trials and secondly, from the incorporation of other theories into cognitive load theory. Both have led to theory expansion. The immediate cause of the so-called “replication crisis” in psychology and other disciplines is a failure to replicate previous empirical findings. Using cognitive load theory as an example, I argue that the appearance of contradictory evidence does not necessarily derive from a failure to properly collect data. Rather, it can be caused by initially insufficiently detailed theories, with increasing detail often revealing the reason for a failure to replicate. For cognitive load theory, each failure to replicate, rather than being a negative, contributed to the further development of the theory. In addition, the theory has developed over many years by closely incorporating other theories associated with human cognitive architecture and evolutionary psychology. In this paper, I discuss some of the developmental milestones associated with cognitive load theory and how they were informed by replication failures and theory integration.