Have you ever been reading a textbook and found that a figure referred to in the text is located over the page? Which means you need to interrupt your train of thought to go looking for the figure, then reintegrate the information into what you were reading a moment ago. This is an example of "split-attention effect", whereby learners are required to divide their attention between two related pieces of information. The result is an increase in extrinsic cognitive load (see post 14/4/14). In other words, the way the information is presented is making you work just that little bit harder to understand the information itself. This in turn puts that little bit more pressure on your working memory, making it harder to commit the information to your long term memory.
On their own, events such as this may have little impact on someone's learning. But when they add up, they can contribute to "cognitive overload". This is where the total (intrinsic plus extrinsic) cognitive load of the instructional material exceeds the learner's working memory and impairs their cognitive processing. Importantly, it is not only publishers of print material that face this kind of challenge. Designers of digital/multimedia resources typically combine several instructional elements including text, still and moving images, narration, music and, in many cases, interactivity. This offers massive freedom and opportunity, but also comes with the risk that the complexity of the resource detracts from its instructional value (Mayer and Moreno, 2003).
Minimising extrinsic load
So what can be done in the design of educational resources to reduce the likelihood of cognitive overload? Two techniques that have been shown to have an impact are contiguity and signaling (or cuing). Contiguity principles involve combining elements - spatially and temporally - in a way that helps the learner to integrate the material. In the example above, this could mean placing text and graphics close together on the same page or, taking things a step further, incorporating critical text into a diagram to avoid split-attention effect. Similarly, in audiovisual materials, concepts conveyed aurally should be tightly integrated with supporting images.
Signalling involves drawing the learner's attention to key aspects of the material. In text based material this could be something as simple as bolding of critical terms or summarising key elements of the text in table form. In multimedia applications, an example would be the use of colour-coded layering of graphics or giving the user the ability to manipulate an image in ways that emphasise important information.
Does it really matter?
In a study by Khalil et al (2010), veterinary students reported that significantly less mental effort was required to interact with a computer based anatomy tutorial designed around Cognitive Load Theory (CLT) principles - including signalling, contiguity and user control - compared with traditional "paper based" resources (class notes and text books) that covered the same material. The computer based module presented a lower total cognitive load, facilitating students' processing of the material.
One of the interesting things about this study is that it involved a subject that is considered very difficult for novice learners. Anatomy is a dense and voluminous field of study that can quickly overwhelm students and cause them to disengage. The authors conclude that the computer based module was not a replacement for the paper based materials, rather that its CLT-based design gave students a means of digesting some of the basic material without experiencing cognitive overload, and that this provided a framework for coping with additional, more complex information from in-depth sources such as text books. This concept of using complementary resources to provide a "scaffold" for learning has exciting potential across a range of educational contexts.
The big picture
Regardless of the type of educational resource, the principles of CLT and good design are the same. As our instructional delivery systems evolve, our understanding of working memory and cognitive capacity provides an important point of reference for designing resources that harness the immense potential of technology while keeping the learner and the learning experience in mind.
Khalil MK, Mansour MM and Wilhite DR (2010). Evaluation of Cognitive Loads Imposed by Traditional Paper-Based and Innovative Computer-Based Instructional Strategies. Journal of Veterinary Medical Education, 37(4), 353-357.
Mayer RE and Moreno R (2003). Nine Ways to Reduce Cognitive Load in Multimedia Learning. Educational Psychologist, 38(1), 43-52.